Method for determining the phoria value of a subject

Abstract

One aspect of the invention relates to a method for determining the phoria value of a subject, the method being implemented by a control module (900) configured to control an automatic refractor head (920) and a selection screen (940). Figure to be published with the abbreviation: Figure 8

Description

Title of the invention: Method for determining a phoria value of a subject TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of optometry.

[0002] In particular, the invention relates to a method, a device and a system for automatically measuring at least one dissociated phoria value of a subject. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Heterophoria corresponds to a deviation of the visual axes when both eyes are at rest. It is only evident when the vision of the two eyes is dissociated. Indeed, when the vision of the two eyes is not dissociated (binocular vision), the brain superimposes and merges the received images (one for each eye) to produce a single image.

[0004] Concretely, this means that in binocular vision, both eyes look towards the same point (in the absence of strabismus), but if one eye is masked, it deviates towards its resting position. When the eye is unmasked, it refocuses thanks to the brain's fusion reflex. This phenomenon is illustrated in Figures 1a and 1b. In [Fig.1a], the subject fixes a target O in binocular vision and the visual axes 110, 120 of the two eyes 130, 140 are oriented towards this target O. Then, as shown in [Fig.1b], one 130 of the subject's eyes (in the example of [Fig.1b], the right eye) is hidden thanks to an object 150, for example an occulting screen. Fusion is then prevented, and the masked eye 130 takes a resting position. If the subject has heterophoria, the visual axis 160 of the masked eye 130 is shifted relative to the visual axis 110 of the same eye 130 when it performs image fusion. This deviation may be in the horizontal plane and / or in the vertical plane.In the example of [Fig.lb], the deviation in the horizontal plane is represented by an angle a formed between the visual axis 160 of the masked eye 130 in the resting position and the visual axis 110 of the same eye 130 in binocular vision. This angle a represents the movement that the eye must perform to return to binocular vision during fusion. When there is no shift between the visual axes 110, 160 in the resting position and in binocular vision, we speak of orthophoria.

[0005] Heterophoria can therefore only be demonstrated when the vision of the two eyes is dissociated, in the absence of fusional stimulus (i.e. when the fusional reflex is prevented). When the divergence (or convergence) also manifests itself in binocular vision, we then speak of tropia or strabismus.

[0006] Heterophoria can be vertical and / or horizontal. In the case of heterophoria horizontal, when the deviation of the visual axis is inward (toward the nose), we speak of esophoria, and when the deviation of the visual axis is outward (toward the temple), we speak of exophoria. In the case of vertical heterophoria, when the deviation of the visual axis is upward, we speak of hyperphoria, and when the deviation of the visual axis is downward, we speak of hypophoria.

[0007] Heterophoria is very common and affects approximately 75% of the population. It is not generally associated with any particular or excessive discomfort, because in the vast majority of cases, the fusion effort required to align the axes of the two eyes in binocular vision is moderate and is done without difficulty. However, when this effort becomes too great, and the subject's reserves of convergence or divergence are insufficient, heterophoria can lead to eye fatigue, headaches, and even double vision problems, which require treatment by an orthoptist to allow the subject visual comfort at all distances.

[0008] To highlight heterophoria and quantify its importance, dissociated phoria measurements are carried out. Dissociated phoria measurements are measurements carried out by dissociating the subject's binocular vision. They are expressed in prismatic diopters and represent the horizontal and / or vertical deviation of the visual axis of one eye of the subject in binocular vision relative to its resting position. In the example of Figures 1a and 1b, the horizontal phoria measurement thus represents the angle α between the visual axis 160 of an eye 130 in the resting position and the visual axis 110 of the same eye 130 when it achieves fusion (and the visual axes 110, 120 of the two eyes point towards the target O that the subject is fixing).

[0009] Equivalently, a phoria value corresponds to the prismatic deviation value of the prism that must be placed in front of the hidden eye (in the resting position) to deviate the visual axis of this eye towards the point that the other, unhidden eye is fixing.

[0010] For the sake of simplification, the "prismatic deviation value" of a prism is also called the "value" of the prism hereinafter. This value is expressed in prismatic diopters (symbol A). It is recalled that one prismatic diopter (1 A) corresponds to a deviation of one centimeter (1 cm) at a distance of one meter (1 m).

[0011] Dissociated phoria values ​​can be measured in distance vision (VL, corresponding to a distance between the subject and the target of approximately 5 meters in France) and in near vision (VP, corresponding to a distance of approximately 40 cm in France), along the vertical axis and along the horizontal axis. For the same subject, 4 phoria values ​​can thus be measured: horizontal phoria in VP, vertical phoria in VP, horizontal phoria in VL, vertical phoria in VL.

[0012] Dissociated phoria measurements are generally carried out in an ophthalmology practice, either by the ophthalmologist himself, or by an orthoptist or by a trained assistant. They can also be carried out in an optical store, by an optician or an optometrist. The phoria measurements obtained are then compared to the subject's fusional reserves and the CA / A ratio in order to detect a potential binocular vision disorder, particularly of the convergence or divergence type. Fusional reserves correspond to the convergence or divergence values ​​that can occur without modifying accommodation or without causing diplopia. The CA / A ratio corresponds to the amount of accommodative convergence induced by accommodation diopters, and is measured using a so-called gradient measurement.

[0013] There are different methods for measuring dissociated phorias, including the masking-unmasking test, the Maddox test, the Thorington test and the Von Graefe test. In all cases, phoria measurements are generally carried out on an individual with compensation (i.e. with corrective lenses). This aims to limit the impact of accommodation on the convergence of the visual axes. Indeed, when the individual accommodates in order to see clearly, the visual axes converge. Thus, if an individual is poorly or not compensated depending on the case, they can, for example, make an additional accommodative effort to see clearly, the measurement of dissociated phorias is impacted (more convergent or more rarely divergent) and therefore does not reflect the real angular deviation of the visual axes. This phenomenon is explained by the near vision triad (miosis, accommodation and convergence) as well as by the desire to merge two clear images.

[0014] The masking-unmasking test consists of placing a mask in front of the subject's eye, then removing the mask and observing the movement of the hidden eye. This examination does not require a refractor head and must be performed by a practitioner trained for this purpose. It cannot be performed by an untrained operator. Unlike the other tests discussed below, this is an objective measure of phoria, in the sense that it does not depend on the subject's responses, but only on the practitioner's technical skill. For this reason, this test requires very good training to quantify heterophoria.

[0015] The Maddox test is based on the use of a cylinder (most often red), called a Maddox cylinder, which gives, from a point of light, an image in the form of a line, for example red, oriented at 90° relative to the axis of the cylinder. The subject must first fix a point of light, then the practitioner places the Maddox cylinder in front of one of the subject's two eyes. The subject then sees two different images: a red line (seen by the eye in front of which the cylinder is placed) and a point of light (seen by the other eye). To determine a phoria value, the practitioner passes prisms having different prismatic deviation values ​​in front of the eye in front of which the Maddox cylinder is placed, and the prismatic deviation value of the prism for which the line and the point are aligned is determined. This prism value corresponds to the phoria value. This test must be carried out by a trained practitioner. Furthermore, the red color of the Maddox cylinder, as well as the large difference between the two images, causes poor accommodation control during the measurement, thus inducing more convergent values. This test is therefore not recommended, especially for non-presbyopic subjects.

[0016] The Thorington test requires two targets: one for distance vision and one for near vision. This test also uses a Maddox cylinder and is subject to the same drawbacks as the Maddox test. In addition, this test can only measure angular deviations of up to 4 A in distance vision, which does not allow for broad screening of the population.

[0017] Finally, the Von Graefe test is the most widely used subjective method for measuring phoria values ​​currently. In the Von Graefe test, a so-called "dissociator" prism is placed in front of one eye of the subject to dissociate the subject's vision. Then, the practitioner passes prisms of different values ​​in front of the subject's other eye, until the subject observes an alignment, on a vertical or horizontal axis, of the images. More precisely, a first so-called realignment prism is placed in front of the subject's second eye. The practitioner then questions the subject about the relative positions of the images and, based on the response, determines the direction of the prismatic variation to be carried out. This method, described in more detail below with reference to [Fig. 2], is a subjective method, which does not rely solely on the practitioner's expertise, unlike the masking-unmasking method.Furthermore, it is not subject to the existing restrictions on non-presbyopic subjects, unlike the Maddox test, and it is suitable for higher phoria values ​​than the Thorington test. However, to be applied correctly, it requires that the practitioner be perfectly trained and accustomed to the procedure.

[0018] As mentioned previously, the above tests are based on complex procedures comprising a series of steps that the practitioner must have in mind and apply in a well-defined order, and for which he must have been specifically trained. These constraints are an obstacle to simplified access to care and the management of visual pathologies in the population. In addition, the quality of the measurements carried out depends greatly on the experience of the practitioner, and it is complicated to obtain a very precise measurement, even for a very experienced practitioner. In addition to requiring the intervention of trained and experienced practitioners, current tests therefore suffer from a problem of reliability and reproducibility. Finally, it is noted that currently, in the Maddox, Thorington and Van Graefe tests, the practitioner must manually vary the values ​​of the prisms which pass in front of the subject.Such manual variation is tedious for the practitioner, and represents a source of error and imprecision in the measurement of phorias.

[0019] The invention improves the situation. Summary of the invention

[0020] The invention offers a solution to the problems mentioned above, by making it possible to automatically scroll the prisms to determine the subject's phoria values, and to allow the practitioner to finely determine a subject's phoria value.

[0021] One aspect of the invention thus relates to a method for determining a phoria value of a subject, the method being implemented by a control module configured to control an automatic refractor head and a selection screen, the method comprising:

[0022] - control the automatic refractor head to place, in a first em placement of the automatic refractor head, a prism called a dissociating prism;

[0023] - control the automatic refractor head to place successively, in a second location of the automatic refractor head distinct from the first location, prisms called realignment prisms, having respective values ​​of prismatic deviation distinct two by two, the values ​​of prismatic deviation of the successive realignment prisms being increasing or decreasing;

[0024] - receive a stop data and, upon receipt of the stop data: • obtaining the prismatic deviation value of the realignment prism upon receipt of the stop data, said value being called the stop value; • control the selection screen to display: • a validation proposal; and • a set of value propositions, each value proposition being associated with a respective prismatic deviation value having a deviation from the stop value less than a predefined deviation;

[0025] - receive at least one instruction corresponding respectively to at least one selecting a value proposition from the set of value propositions;

[0026] - for each instruction received, command the refractor head to place, in the second location, a realignment prism having a prismatic deviation value corresponding to the prismatic deviation value associated with the value proposition corresponding to said instruction;

[0027] - receive validation data corresponding to a selection of the proposal validation;

[0028] - obtain the prismatic deviation value, called final value, of the prism of re alignment upon receipt of validation data; and

[0029] - determine as the subject's phoria value said final value.

[0030] By "the prismatic deviation values ​​of the successive realignment prisms being increasing or decreasing", it is understood that the deviation values prismatic prisms scroll in a predefined order, this order being either ascending or descending. In other words, the values ​​of the realignment prisms are gradually increased or the values ​​of the realignment prisms are gradually decreased.

[0031] The “stop data” corresponds to data received by the control module to stop the scrolling of the realignment prisms. For example, such stop data is received when the subject indicates that he is observing an alignment of the images. The stop value corresponds to the value of the prism placed when the stop data is received. This is a first estimate of the phoria value. Upon receipt of such stop data, the practitioner can readjust the value of the prism around the stop value. Indeed, the stop value may not correspond exactly to the phoria value, for example because the practitioner stopped the scrolling a little too late compared to the moment when the subject indicated that he was observing an alignment, or because the subject indicated a little too late that he was observing an alignment. The practitioner can then, for example, "go back" by a few half prismatic diopters or a few prismatic diopters.

[0032] By "obtaining the prismatic deviation value of the realignment prism upon receipt of the stop data, said value being called the stop value", it is understood to mean obtaining any value associated with the prismatic deviation value of the prism upon receipt of the stop data. This may be the prismatic deviation value, but also, for example, a prism number - it being understood that it is possible to determine the prismatic deviation value from the prism number. For example, the prism of number i may correspond to the i-th prism placed in front of the subject's eye, regardless of the initial value of the prism and the direction (increasing or decreasing) of the prismatic variation. From the initial value of the prism, the direction of variation and the variation step, it is possible to determine the prismatic deviation value from the prism number.

[0033] The set of value propositions comprises at least one value proposition. By "value proposition associated with a respective prismatic deviation value" it is understood that the value proposition is linked to a prismatic deviation value. Such a value proposition may be a prismatic deviation value, a prism number, etc.

[0034] Each value proposition corresponds to a value “around” the stop value that the user can test. By “prismatic deviation value having a deviation from the stop value less than a predefined deviation”, it is understood that the VS value(s) (for “selectable values”) of the set of value propositions are such that IVS - VAI < a, where VA is the stop value and a the predefined deviation. The constraint can of course be stronger. For example, in certain embodiments, the VS values ​​are chosen from “already past” values:

[0035] - if, during the successive placement of the prisms, the values ​​were increasing, the VS values ​​are between VA - a and VA;

[0036] - if, during the successive placement of the prisms, the values ​​were decreasing, the VS values ​​are between VA and VA + a.

[0037] The validation data is received for example when the user indicates that he observes an alignment of the images with the current value of the prism. Upon receipt of such validation data, the current value, i.e. the value of the realignment prism at the time when the validation data is received, is recorded and corresponds to the phoria value.

[0038] It is noted that "obtaining the final value" corresponds to the "direct" reception of the final prismatic deviation value, or to the reception of data making it possible to determine the final prismatic deviation value, for example the prism number ("indirect" obtaining).

[0039] It is noted that, traditionally, the dissociating prism is placed in front of the right eye and the realigning prism is placed in front of the left eye, but this is not mandatory.

[0040] It is also noted that the above method can be implemented in distance vision and / or in near vision.

[0041] In some embodiments, the realignment prisms are placed successively with a frequency between 0.5 Hz and 2 Hz.

[0042] This means that the time difference between two consecutive placements is fixed and between 0.5 seconds and 2 seconds. For example, the frequency can be equal to 1 Hz. Such values ​​allow scrolling fast enough so that the duration of the phoria measurement remains reasonable, but long enough so that there is not (too much) delay between the moment when the subject detects an alignment and the moment when a stop data is received by the control module.

[0043] In some embodiments, the prismatic deviation values ​​of the successive realignment prisms are spaced apart by a predefined fixed pitch, between 0.5 A and 1 A.

[0044] This makes it possible to test successive values ​​that are close enough to obtain a stopping value that already constitutes a good estimate of the phoria value.

[0045] It is noted that it is complicated, if not impossible, to scroll realignment prisms regularly in manual methods. This results in a longer measurement time, which distorts the measurement. These problems are avoided with the automatic method of the invention.

[0046] In some embodiments, the set of value propositions comprises value propositions associated with values ​​that belong to the prismatic deviation values ​​of the successive realignment prisms and the predefined deviation is between 0.5 A and 2 A.

[0047] In these embodiments, it is only possible to place in front of the subject's eye prismatic deviation values ​​that have already passed, and which are at most 2 A away from the stop value.

[0048] In some embodiments, the method further comprises:

[0049] - command the selection screen to display a progress line including a plurality of positions representing prismatic deviation values;

[0050] - at each placement of a realignment prism among the realignment prisms successive, command the selection screen to display a symbol linked to the prismatic deviation value of the placed realignment prism, the symbol being superimposed on its corresponding position in the advancement line.

[0051] The advancement line is for example a graduated line whose graduations correspond to different prismatic deviation values. This advancement line is typically displayed before the realignment prisms begin to scroll. As soon as the realignment prisms begin to scroll, the symbol linked to the current prismatic deviation value also scrolls on the selection screen. The symbol can be a prism number, or a prismatic deviation value, or any other symbol linked to the current prismatic variation value.

[0052] This allows the practitioner to quickly see where the phoria measurement is.

[0053] In particular, each value proposition among the set of value propositions can be displayed at the position, in the progress line, corresponding to the prismatic deviation value linked to said value proposition.

[0054] For example, the value propositions may be displayed as selectable areas on the selection screen. This allows the practitioner to more easily select values ​​"around" the stop value.

[0055] In particular, the method may comprise:

[0056] - upon receipt of an instruction corresponding to a selection of a proposal of value from among the set of value propositions, controlling the selection screen to display a representation indicating said value proposition, said representation being displayed at a location distinct from the position, in the advancement line, corresponding to the prismatic deviation value related to said value proposition.

[0057] This embodiment is particularly advantageous when the selection screen is a touch screen. When the user selects an area on the progress line, he hides the corresponding symbol with his finger and no longer sees the symbol or what is displayed on the area. To overcome this drawback, it is therefore proposed to display a representation of the tested value (for example, a duplication of the symbol, possibly of a larger size), at a distance from the progress line. and therefore the user's finger.

[0058] In some embodiments, the phoria value is a horizontal phoria value, wherein an optotype is placed in front of two eyes of the subject, wherein the dissociating prism is a vertical prism, such that the subject sees two images of the optotype respectively located on two distinct horizontal planes. The method may further comprise:

[0059] - after having commanded the automatic refractor head to place the prism dis sociator in the first location, receive initial vertical positioning data including: • information indicating whether the subject sees two images of the optotype on the same vertical plane or on two separate vertical planes after placement of the dissociating prism; and • when the subject sees the two images of the optotype on two separate vertical planes, information describing a relative position of the two images of the optotype perceived by the subject;

[0060] - determine, based on the initial vertical positioning data received, a horizontal prism type and an initial prismatic deviation value;

[0061] wherein the successive realignment prisms are of the determined horizontal prism type;

[0062] wherein the respective prismatic deviation values ​​of the successive realignment prisms are ordered from the determined initial prismatic deviation value.

[0063] After placing the dissociating prism, the subject therefore sees two images of the optotype on two distinct horizontal planes, one being “lower” than the other.

[0064] By "information describing a relative position of the two images of the optotype", is meant information indicating how the subject positions the two images relative to each other. In particular, such information makes it possible to indicate which image, among the top image and the bottom image, the subject sees on the right and which image the subject sees on the left.

[0065] The type of horizontal prism can be: internal base prism or external base prism.

[0066] In these embodiments, the initial value of the realignment prism, as well as the direction of variation of the successive values ​​of the prisms, are advantageously determined as a function of the way in which the subject sees the images of the optotype relative to each other after placement of the dissociating prism. This makes it possible to approach, from the positioning of the realignment prism, the horizontal phoria value of the individual. In other words, the initial value of the realignment prism is advantageously chosen to approach, from the start, the phoria value of the subject and thus avoid scrolling through too many prism values ​​until achieve alignment, unlike the Van Graefe reference test, in which the type and initial value of the realignment prism are predetermined and are the same for all subjects (usually a 12-15 A internal base prism).

[0067] In particular, control of the automatic refractor head for successively placing the realignment prisms may comprise:

[0068] - command the automatic refractor head to place a first re prism alignment having a prismatic deviation value corresponding to the determined initial prismatic deviation value;

[0069] - receive new vertical positioning data comprising: • information indicating whether the subject sees the two images of the optotype on the same vertical plane or on two separate vertical planes after placement of the first realignment prism; and • when the subject sees the two images of the optotype on two separate vertical planes after placement of the first realignment prism, information describing a relative position of the two images of the optotype perceived by the subject;

[0070] - determine, from the new vertical positioning data, whether the values of prismatic deviation of successive realignment prisms are increasing or decreasing.

[0071] Thus, according to these embodiments, the subject is asked how he perceives the positions of the images relative to each other after placement of the initial realignment prism. The direction in which the modification of the prismatic deviation value of the realignment prism is carried out (increase or decrease) is then determined from the subject's response.

[0072] In alternative embodiments, the phoria value is a vertical phoria value, wherein an optotype is placed in front of two eyes of the subject, wherein the realignment prisms are vertical prisms. The method may further comprise:

[0073] - receive a horizontal heterophoria type and a horizontal phoria value from the subject ;

[0074] - determine, from the type of heterophoria and the horizontal phoria value received, a horizontal prism type and a horizontal prismatic deviation value;

[0075] wherein the dissociating prism is a prism of the determined horizontal prism type having as prismatic deviation value the determined horizontal prismatic deviation value.

[0076] In these embodiments, a previously received or determined horizontal phoria value is advantageously used to determine the vertical phoria value of the subject (i.e., to carry out the measurement of the vertical phoria value of the subject). More In particular, this horizontal phoria value is used to choose the type of horizontal prism and the prismatic deviation value of the dissociation prism to be placed in front of one of the subject's eyes to measure the vertical phoria value. This ensures adequate dissociation of the optotype images on two vertical planes (in particular so that these planes are neither too close together nor too far apart, which, in both cases, could impair the subject's assessment of the horizontal alignment of the images when changing the value of the realignment prism).

[0077] Another aspect of the invention relates to a device for determining a phoria value of a subject, configured to control an automatic refractor head and a selection screen, the device being configured to:

[0078] - control the automatic refractor head to place, in a first em placement of the automatic refractor head, a prism called a dissociating prism;

[0079] - control the automatic refractor head to place successively, in a second location of the automatic refractor head distinct from the first location, prisms called realignment prisms, having respective values ​​of prismatic deviation distinct two by two, the values ​​of prismatic deviation of the successive realignment prisms being increasing or decreasing;

[0080] - receive a stop data and, upon receipt of the stop data: • obtaining the prismatic deviation value of the realignment prism upon receipt of the stop data, said value being called the stop value; • control the selection screen to display: • a validation proposal; and • a set of value propositions, each value proposition being associated with a respective prismatic deviation value having a deviation from the stop value less than a predefined deviation;

[0081] - receive at least one instruction corresponding respectively to at least one selecting a value proposition from the set of value propositions;

[0082] - for each instruction received, command the refractor head to place, in the second location, a realignment prism having a prismatic deviation value corresponding to the prismatic deviation value associated with the value proposition corresponding to said instruction;

[0083] - receive validation data corresponding to a selection of the proposal validation;

[0084] - obtain the prismatic deviation value, called final value, of the prism of re alignment upon receipt of validation data; and

[0085] - determine as the subject's phoria value said final value.

[0086] Another aspect of the invention relates to a system for determining a phoria value of a subject comprising a device as defined above, a re- automatic fractionator and a selection screen.

[0087] A computer program, implementing all or part of the method described above, installed on pre-existing equipment, is in itself advantageous.

[0088] Thus, the present invention also relates to a computer program comprising instructions for implementing certain steps of the method described above, when this program is executed by a processor.

[0089] This program may use any programming language (for example, an object-oriented language or other), and be in the form of interpretable source code, partially compiled code or fully compiled code.

[0090] The [Fig.8] described in detail below can form the flowchart of the general algorithm of such a computer program.

[0091] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0092] Other characteristics and advantages of the invention will appear on reading the description, which can be read in conjunction with the figures. These figures are presented for information purposes only and in no way limit the invention.

[0093] [Fig. 1a], [Fig. 1b] Figures 1a and 1b represent an example of heterophoria in a subject.

[0094] [Fig.2] [Fig.2] represents an example of a flowchart representing steps implemented during a Von Graefe test according to the state of the art.

[0095] [Fig.3a], [Fig.3b], [Fig.3c], [Fig.3d] Figures 3a, 3b, 3c and 3d represent examples of prisms of the state of the art.

[0096] [Fig.4a], [Fig.4b] Figures 4a and 4b represent images seen by a subject during vertical dissociation and during horizontal dissociation of vision respectively.

[0097] [Fig.5a], [Fig.5b], [Fig.5c], [Fig.5d] Figures 5a, 5b, 5c and 5d represent examples of information and proposals displayed on the selection screen during a method of measuring a phoria value according to one or more embodiments of the invention.

[0098] [Fig.6] [Fig.6] represents a flowchart of a method for determining a horizontal phoria measurement according to one or more embodiments of the invention.

[0099] [Fig.7] [Fig.7] shows steps for determining a vertical phoria measurement according to one or more embodiments of the invention.

[0100] [Fig.8] [Fig.8] represents an example of a flowchart of a method for determining a phoria measure according to the invention.

[0101] [Fig.9] [Fig.9] represents a system in which a method of determining of a phoria measurement according to one or more embodiments of the invention can be implemented.

[0102] [Fig. 10] [Fig. 10] shows a device for determining a phoria measure in one or more embodiments of the invention. DETAILED DESCRIPTION

[0103] As mentioned above, the Von Graefe test is the most widely used subjective method currently in France and in a number of countries around the world. It is now generally used with a manual refractor head, on which the practitioner moves prisms in front of the subject's eyes. The test generally lasts between 5 and 10 minutes and can only be performed by a trained practitioner who has fully mastered the procedure.

[0104] The Von Graefe test schematically comprises four or five steps:

[0105] - two steps carried out in distance vision (VL, corresponding to a subject located at a target distance of approximately 5 m in France, 6 m in Anglo-Saxon countries): one to determine a horizontal VL phoria measurement and one to determine a vertical VL phoria measurement;

[0106] - two steps carried out in near vision (NP, corresponding to a subject located at a target distance of approximately 40 cm in France, more generally 33 cm in Anglo-Saxon countries): one to determine a horizontal phoria measurement VP and one to determine a vertical phoria measurement VP; and

[0107] - an additional step called “gradient measurement” carried out only on the non-presbyopic subjects under 40 years old and carried out in VP.

[0108] Horizontal and vertical measurements are carried out in the same way in VP and VL. The only differences between VP and VL measurements are the distance from the subject to the target and possibly the type of target (generally, a single optotype for VL and a series of optotypes for VP).

[0109] [Fig. 2] represents an example of a flowchart of a method for measuring phorias of a subject according to the prior art, based on a Von Graefe test. More precisely, [Fig. 2] represents steps for measuring phorias in distance vision or in near vision. Thus, the steps of [Fig. 2] can be implemented twice, successively: once to determine the values ​​in distance vision, and another time to determine the values ​​in near vision. Conventionally, the values ​​in distance vision are determined before the values ​​in near vision.

[0110] It is noted that the Von Graefe test is performed while the subject is wearing the correction (or compensation) adapted to his eyesight. Thus, during a step 210 (optional if the subject does not need compensation), the optimal compensation determined for the subject or the subject's usual compensation can be placed in front of the subject's eyes, in the refractor head.

[0111] During a step 220, an optotype may be displayed in front of the subject's eyes, for example an isolated letter (or an isolated symbol) or a set of letters (or symbols), such as a row or a column of letters. The optotype is located on the other side of the compensation relative to the subject's eyes. As mentioned previously, the optotype (also called a "target") is typically a single letter (or a single symbol) in distance vision and a set of letters (or a set of symbols) in near vision.

[0112] Then, the horizontal phoria value (in VP or in VL) is measured during a step 230.

[0113] To measure the horizontal phoria value (step 230), we begin by dissociating the vision (step 231), in order to allow the visual axes to take a resting position. We then voluntarily induce double vision in the subject. The creation of artificial double vision allows the ocular pair to take its passive position (without fusional effort). To dissociate the vision, it is common to place a prism, called a dissociating prism, on one of the patient's eyes. To determine horizontal phorias, the dissociating prism is a vertical prism and induces a vertical dissociation of the vision. Traditionally, the dissociating prism is a top-base prism placed in front of the right eye having a value equal to 6 A.

[0114] Figures 3a and 3b respectively represent a lower base prism and an upper base prism, which are two types of vertical prisms. It is recalled that a prism is a glass whose two surfaces (or, more broadly, the planes tangent to the two surfaces of the glass) are inclined relative to each other (i.e. form a non-zero finite angle). The thinnest part at the edge of the prism is called the "vertex", and the thickest part is called the "base". By "vertical prism", we mean a prism whose vertex-base axis is vertical (i.e. in the longitudinal axis of the patient's body, generally perpendicular to the axis passing through the centers of the patient's two eyes). A lower base prism, as shown in [Fig.3a], has the base directed towards the bottom of the subject's face. An upper base prism, as shown in [Fig.3b], has the base directed towards the top of the subject's face.

[0115] At the end of step 231, the patient's vision is vertically dissociated, and the patient sees two images of the optotype located on two separate horizontal planes. For example, when the vision is dissociated by placing a top-base prism in front of the right eye and the optotype is a single letter, the subject sees two images of the optotype one above the other, as shown in [Fig. 4a]: an image 410 of the optotype at the top, seen by the left eye, and an image 420 of the optotype at the bottom, seen by the right eye. It is noted that in [Fig. 4a], images 410 and 420 are shown aligned vertically. However, this is not necessarily the case. Depending on the values ​​of horizontal phorias of the subject, the latter can see the images 410 and 420 aligned vertically, or offset vertically relative to each other, in one direction or the other. It is noted that the relative vertical position of the images perceived by the subject after placement of the dissociating prism is not used in the Van Graefe test.

[0116] It is noted that if a lower base prism were placed in front of the right eye, the subject would still see two images of the optotype on two separate horizontal planes, but it would be the image seen by the right eye that would be above the image seen by the left eye. Similarly, if the upper base prism had been placed in front of the subject's left eye, the image seen by the right eye would be located above the image seen by the left eye. Finally, if a lower base prism had been placed in front of the left eye, the image seen by the left eye would be located above the image seen by the right eye.

[0117] In step 233, a horizontal initial prism is placed in front of the subject's other eye (here, the left eye). Typically, the initial prism is an internal base prism having a value equal to 12 A.

[0118] Figures 3c and 3d respectively represent an internal base prism and an external base prism, which are two types of prisms. By "horizontal prism", we mean a prism whose vertex-base axis is horizontal (i.e. perpendicular to the longitudinal axis of the patient's body, generally in the axis passing through the centers of the patient's two eyes). In Figures 3c and 3d, the eye represented is the patient's left eye. An internal base prism, as represented in [Fig.3c], has the base directed towards the subject's nose. An external base prism, as represented in [Fig.3d], has the base directed on the other side relative to the nose (towards the temple of the side considered).

[0119] The practitioner then questions the subject about the relative vertical positions of the two images (top image and bottom image). For example, the practitioner questions the subject about the position of the bottom image relative to the top one (shifted to the right, shifted to the left, or aligned vertically). Depending on the response given (step 235), the practitioner determines the direction of the prismatic variation to be carried out.

[0120] If the subject responds that the two images are not vertically aligned (exit from step 235, arrow “N”), the practitioner modifies (step 237) the prismatic deviation value of the horizontal prism (also called “realignment prism”). In the example considered (dissociating prism with upper base in front of the right eye and realignment prism with internal base in front of the left eye), if the subject sees the bottom image shifted to the left relative to the top image, the practitioner increases the prismatic deviation value of the horizontal prism. Conversely, if the subject sees the bottom image shifted to the right relative to the top image, the practitioner decreases the prismatic deviation value.

[0121] Typically, during successive steps 237, the practitioner modifies (increases or decreases) the prismatic deviation value of the horizontal prism in steps of 1 A.

[0122] At the end of step 237, step 235 is implemented again: the practitioner asks the patient for the relative vertical position of the two images.

[0123] If, at the end of a step 235, the subject responds that the two images are aligned vertically (exit from step 235, arrow “O”) - i.e. on the same vertical plane, as in [Fig.4a] - the test stops (step 239), and the practitioner notes the “current” value of the horizontal prism. By current value, we mean the value of the prismatic deviation of the horizontal prism used during the last performance of step 235, at the end of which the subject responded that he saw the two images aligned vertically. In other words, this current value can be (rare case) the initial value of the horizontal prism, set in step 233, or the value modified during step 237 immediately preceding a positive response from the user regarding the vertical alignment of the two images.

[0124] This current value recorded in step 239 corresponds to the value of the horizontal dissociated phoria of the subject. The direction of the horizontal dissociated phoria is determined from the type of prism for which the final alignment is obtained. In the example above, if it is an internal base prism, the subject has exophoria, and if it is an external base prism, it is esophoria.

[0125] During a step 240, the vertical phorias are measured. To do this, we start by horizontally dissociating the vision (step 241), by placing a horizontal dissociating prism in front of one of the subject's eyes. Conventionally, the dissociating prism is an internal base prism placed in front of the subject's left eye, having a value between 12 and 15 A.

[0126] The patient's vision is then dissociated horizontally, and the patient sees two images located on two distinct vertical planes. For example, if an internal base prism is placed in front of the left eye, the subject sees two images of the optotype next to each other, as shown in [Fig.4b]: an image 430 of the optotype on the left, seen by the left eye, and an image 440 of the optotype on the right, seen by the right eye. It is noted that in [Fig.4b], images 430 and 440 are shown aligned on the same horizontal plane, but this is not necessarily the case. Depending on the subject's vertical phoria values, the subject may see images 430 and 440 aligned in the same horizontal plane, or vertically offset from each other (i.e. in two distinct horizontal planes), in one direction or the other.

[0127] If, after the placement of the dissociating prism in step 241, the subject sees the two images aligned on the horizontal plane, the vertical phoria value is set to zero (step 249). In other words, this corresponds to an absence of vertical phoria (which is generally expected).

[0128] Otherwise, if the subject does not see the two horizontally aligned images, a vertical realignment prism is placed in front of the subject's other eye (here, the right eye) during a step 243. This prism is typically a top or bottom base prism having a value equal to 0.5 A.

[0129] The practitioner then questions the subject about the horizontal alignment of the two images (left image and right image). For example, the practitioner questions the subject about the position of the left image relative to the right image (higher, lower, or horizontally aligned). Depending on the response given (step 245), the practitioner determines, if applicable, the direction of the prismatic variation to be carried out.

[0130] If the subject responds that the two images are not horizontally aligned (exit from step 245, arrow “N”), the practitioner modifies (step 247) the prismatic deviation value of the realignment prism.

[0131] Typically, during successive steps 247, the practitioner modifies (increases or decreases) the prismatic deviation value of the vertical prism in steps of 0.5 A.

[0132] At the end of step 247, step 245 is implemented again: the practitioner asks the subject how the images are located relative to each other in horizontal planes.

[0133] If, at the end of a step 245, the subject responds that the two images are aligned horizontally (exit from step 245, arrow “O”), the test stops (step 249), and the practitioner notes the “current” value of the realignment prism, i.e. the value of the realignment prism at the last time step 245 was performed, at the end of which the subject responded that he saw the two images aligned horizontally. In other words, this current value can be the initial value of the vertical prism, set at step 243, or the value modified at step 247 immediately preceding a positive response from the user regarding the horizontal alignment of the two images.

[0134] This current value recorded in step 249 corresponds to the value of the subject's vertical dissociated phoria (in VL or in VP). The direction of the vertical dissociated phoria can be determined from the type of realignment prism for which the alignment is obtained.

[0135] In the non-presbyopic subject, an additional step not shown in [Fig.2] can be implemented, only in near vision: the measurement of the gradient. This additional step makes it possible to determine the link existing between the ac-commodative convergence and the accommodation (CA / A ratio). This method determines the impact of the accommodation on the convergence of the visual axes. This allows the practitioner to determine the treatment adapted to the subject (wearing an addition, rehabilitation, addition of prisms, etc.). To determine the gradient, a second measurement of horizontal dissociated phorias is carried out in near vision only, with the addition, on both eyes, of a +1.00 diopter lens on the distance vision correction. The practitioner ensures beforehand that the addition of this +1.00 diopter lens does not cause blurred vision in the subject. The measurement of the gradient is known from the state of the art and is not not detailed further here.

[0136] It appears from the above description that the Van Graefe test is delicate and laborious to implement. For each phoria measurement, the practitioner must manually place the dissociating prism on one eye, place a realignment prism on the other eye, question the subject on the relative position of the images, and interpret the subject's response to determine in which direction the prismatic variation should be carried out (increase or decrease the value of the realignment prism, which requires continual gymnastics since the subject's perception is inverted with respect to the prisms that must be introduced). Then, the practitioner must manually vary the values ​​of the realignment prism, which in itself constitutes an obstacle to a precise determination of the value of the measurement (it is not easy to precisely modify the values ​​of the realignment prism with the refraction heads, especially when they are manual).

[0137] Since these steps are repeated to carry out the vertical and horizontal measurements, in VP and VL, the number of manipulations and the risk of error in the correct interpretation of the subject's responses make this test a long and tedious method for the practitioner, as well as for the subject. In addition, the practitioner must determine, from the relative positions of the letters indicated by the subject, the direction of the heterophoria, which can lead to inversions. Finally, the variation of the prisms on a manual refraction head is done using a wheel. The accuracy of the measurement can therefore be impacted by the variation of the prisms which can be less regular and by the time which can be extended. The reaction time of the practitioner also impacts this accuracy.

[0138] These constraints constitute an obstacle to systematic monitoring of binocular vision, which is often neglected at present when a subject comes for eye examinations.

[0139] The invention proposes, to overcome the above problems, to automate the phoria measurements, by using an automatic refractor head controlled by a control device. The control device comprises a control module configured to send control signals to the automatic refractor head. The control device may comprise or be connected to a selection screen (for example a screen connected to an input device, such as a mouse and / or a keyboard, or a touch screen) configured to display proposals to a user and to receive at least one selection of at least one of the displayed proposals. Upon receipt of a control signal, the automatic refractor head is configured to place at least one prism in front of an eye of the subject. The automatic refractor head comprises two locations, each location corresponding to a respective eye, capable of receiving prisms.

[0140] For example, a control signal may include:

[0141] - a first data indicating in front of which eye the prism must be placed (i.e. in which location of the refractor head the prism should be placed);

[0142] - a second data corresponding to the type (internal base, external base, in base lower or upper base) of the prism to be placed;

[0143] - a third data corresponding to the prismatic deviation value of the prism to place.

[0144] Upon receipt of such a control signal, the refractor head places, in the location associated with the first data item, a prism of the type indicated by the second data item and having a value indicated by the third data item.

[0145] The above example corresponds to a control signal to control the placement of a single prism. The control signal can also control successive placements of prisms.

[0146] For example, the control signal may include a field indicating whether it concerns the placement of a single prism or successive prisms, and, if it concerns the placement of successive prisms, additional fields including a fourth data item corresponding to the direction of prismatic variation (scrolling in the increasing or decreasing direction of the prismatic deviation values), a fifth data item corresponding to the pitch (i.e. the difference, in prismatic diopters, between two successive prism values) and a sixth data item corresponding to the frequency of change (i.e. the duration between two successive prism placements). These fields may be set by default to predefined values, for example 1 A and 1 second, which are modified only if the control signal includes other values.

[0147] To control a scrolling of realignment prisms having successive prismatic deviation values ​​(increasing or decreasing), the realignment module can: either send a single control signal to control the successive placement of the prisms (as in the second case above), or successively send several control signals, each control signal controlling the placement of a single prism (as in the first case above). In the latter case, the control signals can be sent by the control module to the automatic refractor head with a predefined frequency and pitch.

[0148] It is thus possible to automatically implement phoria measurement methods, in particular the Van Graefe test (but the invention is not limited to this test).

[0149] A first example of implementation of a method for measuring a phoria value according to the invention is detailed below. In this example, the choice of the initial values ​​of the prisms and the direction of prismatic variation are similar to the Van Graefe test, but implemented automatically, as is the scrolling of the prisms in front of the subject's eyes (unlike the state-of-the-art Van Graefe test, which is implemented entirely manually).

[0150] First, the practitioner can select a proposal (for example, "start") displayed on the selection screen to begin a phoria measurement examination. Upon receiving the selection of the proposal, the selection screen can display fields, which the practitioner can fill in, corresponding to compensation values ​​of the subject. Once the practitioner has entered and validated these values, the control module (connected to the selection screen) sends a control signal to the refractor head to place, in front of the two eyes of the subject, lenses corresponding to the compensation values ​​received (automation of step 210 of [Fig. 2]). Alternatively, these values ​​can be directly retrieved, for example from a digital file of the subject, or from an eye examination carried out upstream on a system controlled by the control device.

[0151] Then, the selection screen can display one or more proposals corresponding to the measurement to be carried out (for example, the type of phoria: horizontal or vertical, the type of vision: VL or VP, a start button to start the measurement). Alternatively, a single proposal to start the examination is displayed (the types of phorias and the types of vision then being in a predefined order). Upon receipt of the practitioner's responses, the control module can control a screen to display an optotype (automation of step 220 of [Fig.2]).

[0152] Then, the control module sends a control signal to the refractor head to place, in front of a (predefined) eye of the subject, the dissociating prism (the type and value of which are selected, from a set of predefined values, by the control module depending on the type of phoria measured). This corresponds to steps 231 or 241 of [Fig. 2]. Optionally, after placement of the dissociating prism, the selection screen can display a question to validate that the subject is indeed seeing double, and the practitioner can validate that the subject is seeing double, or indicate that the subject is not seeing double. In the latter case, the control module can command the refractor head to place a dissociating prism having a value greater than the previous value.

[0153] Then, the control module sends a control signal to the refractor head to place, in front of the other eye of the subject, the initial realignment prism (the type and value of which are selected, from a set of predefined values, by the control module depending on the type of phoria measured). This corresponds to steps 233 and 243 of [Fig.2].

[0154] A question as well as several propositions concerning the relative positions of the images perceived by the subject can then be displayed on the selection screen, and, depending on the answer(s), the control module sends a signal of command to the refractor head to scroll realignment prisms in front of the subject's second eye, increasing or decreasing the prismatic deviation values, with a predefined frequency and pitch (steps 237 and 247 of [Fig.2]).

[0155] At the same time as the realignment prisms scroll in front of the subject's second eye, a stop proposal is displayed on the selection screen, and allows the practitioner to stop the scrolling. In particular, the practitioner can select this proposal as soon as the subject indicates that he sees the two images of the optotype aligned on the same vertical or horizontal plane (depending on the type of phoria measured).

[0156] The selection of the stop proposal corresponds to a stop data item received by the selection screen: upon receipt of this stop data item:

[0157] - the scrolling of the realignment prisms is stopped (in the case where only one signal of placing command of successive realignment prisms is sent to start the scrolling, a stop signal can be sent from the control module to the automatic refractor head, and in the case where several placing command signals of a realignment prism are successively sent, the control module can simply stop sending such command signals);

[0158] - the current value of the realignment prism is read (for example stored in a memory of the control device). This value is subsequently called the “stop value”; and

[0159] - several proposals are displayed on the selection screen.

[0160] The displayed proposals include a validation proposal and a set of value proposals.

[0161] The set of value propositions comprises at least one value proposition. Each value proposition is associated with a respective prismatic deviation value (referred to as a "selectable value"). Two value propositions are associated with two distinct prismatic deviation values.

[0162] For example, the selectable values ​​may correspond to prismatic deviation values ​​that have already been proposed to the subject and which are at most a predetermined deviation away from the stop value. For example, in the case of a scrolling of the prisms in the increasing direction of prismatic deviation, if the stop value is equal to 8 A and the predetermined deviation is 1 A, the selectable values ​​may be: {7A; 8A}, or {7A, 7.5 A; 8 A}. It is noted that the stop value may be part of the selectable values ​​(to allow the practitioner to test, for example, the value 7 A and then return to the value 8 A if the subject confirms that he does not observe alignment for 7 A).

[0163] This allows for more fine-tuning of the realignment prism value for which alignment is observed. Indeed, the stop value may not be exactly equal to the value for which alignment is observed for several reasons:

[0164] - the subject's response time: the subject says "stop" at 8 A, but he perceived the alignment at 7 A. So he said "stop" a little too late; or

[0165] - the practitioner's reaction time: the subject said "stop" when the cursor was on the number 7, but when the practitioner stopped scrolling, the cursor had moved to 8 A.

[0166] In some embodiments, the selectable values ​​may also include values ​​corresponding to prismatic deviation values ​​that have not yet been proposed to the subject and that are at most a predetermined deviation away from the stop value. For example, in the case of a scrolling of the prisms in the increasing direction of prismatic deviation, if the stop value is equal to 8 A and the predetermined deviation is 1 A, the selectable values ​​may be: {7A; 8A; 9A], or {7 A, 7.5 A; 8 A; 8.5 A; 9 A}. Such embodiments make it possible to manage cases where, in a hurry, the subject says "stop", but in fact the images are not completely aligned. He therefore said "stop" a little too early. Alternatively, in such situations, the method may be restarted from the beginning (the possibility of adjusting with values ​​that have not yet been tested is not left).

[0167] Examples of information displayed on the selection screen during measurement of a phoria value are shown in Figures 5a to 5d.

[0168] As illustrated in [Fig.5a], before starting to scroll through the prisms, the selection screen may display an advancement line 510 comprising a plurality of positions representing possible prismatic deviation values. For example, the advancement line 510 may be a graduated ruler, each graduation of which corresponds to a prismatic deviation value. A symbol 520 is also displayed. This symbol may, for example, correspond to the prism number (prism number i therefore corresponding to the i-th prism placed in front of the subject's eye). It is noted that the prismatic deviation value of the realignment prism can always be determined from the prism number, provided that the initial value of the prism, the direction of prismatic variation and the step of scrolling of the prism values ​​are known. For example, the symbol 520 is superimposed on its corresponding position on the advancement line 510, as shown in [Fig.5a].The selection screen can display three proposals 530, 540 and 550. .

[0169] Proposition 530 corresponds to an instruction to start the scrolling of the realignment prisms: as soon as the practitioner selects this proposition 530, the control module sends one or more control signals to command the refractor head to scroll successive prisms.

[0170] Proposition 540 corresponds to an instruction to stop the scrolling of the realignment prisms. Proposition 550 corresponds to a validation instruction. As long as prism scrolling has not started, proposals 540 and 550 are not selectable.

[0171] Of course, other elements may be displayed on the selection screen. For example, before the proposition 530 corresponding to the instruction to start the scrolling of the prisms, an examination instruction may be displayed on the selection screen and / or read to the subject (by the practitioner, or by a synthesized voice broadcast by a loudspeaker connected to the control module). This instruction may be, for example: “Stare at the bottom letter. Glasses will scroll in front of your eyes. Say stop as soon as the bottom letter is aligned with the top one.”

[0172] When the user selects the proposition 530 corresponding to the instruction to start the scrolling of the prisms, the scrolling of the successive realignment prisms begins. At each change of prism, the corresponding value can be displayed on the progress line 510, as shown in [Fig.5b].

[0173] As shown in [Fig.5b], a symbol 560 corresponding to the current value of the realignment prism is displayed on the selection screen, for example superimposed on the advancement line 510. Thus, successive symbols 560 can scroll on the screen to display the current value or the number of the realignment prism, which allows the practitioner to know very quickly and simply where the prisms are in the scrolling. During the scrolling of the prisms, the proposition 540 corresponding to the stop instruction is selectable, and the propositions 530 and 550 are not selectable. In certain embodiments, during the scrolling of the prisms, the prism values ​​are dictated, for example via a loudspeaker connected to the control module. Thus, as soon as a new prism is placed in the automatic refractor head, a sound indicating the prism value or the prism number is emitted.

[0174] When the subject sees the two aligned images, the proposition 540 corresponding to the stop instruction is selected, for example by the practitioner. Other embodiments are possible. For example, the subject whose phoria values ​​are being measured can actuate a button which sends stop data to the control module. According to another example, the control device can comprise a microphone connected to a voice recognition module, and, when the subject says “stop”, the scrolling of the prisms is automatically stopped.

[0175] As shown in [Fig.5c], upon receipt of the stop data, the scrolling of the prisms is stopped, and the symbol 570 displayed is that corresponding to the number of the realignment prism for which the subject indicated that he was observing an alignment. Several proposals are then selectable: proposal 550 corresponding to the validation proposal, as well as a set of value proposals 580a, 580b corresponding to different selectable values.

[0176] For example, the value propositions 580a, 580b are located at the positions corresponding to the different selectable values, on the advancement line 510.

[0177] The practitioner then has the possibility:

[0178] - either to validate the stop value via proposition 550. In this case, it is this value that is recorded as the subject's phoria value;

[0179] - either to select a value proposition 580a, 580b. In this case, a prism having a prismatic deviation value corresponding to the value proposition is displayed in front of the subject's relevant eye.

[0180] As shown in [Fig.5d], in certain embodiments, when the practitioner selects a value proposition 580a, a symbol 590 indicating the prismatic deviation value associated with said value proposition 580a is displayed at a distance from the value proposition 580a. These embodiments are particularly advantageous in the case where the selection screen is a touch screen and the practitioner selects the different propositions with his finger. Indeed, in this case, when the practitioner places his finger on the value proposition 580a, he hides the corresponding prismatic deviation value. Thus, displaying this value at a location 590 distant from the advancement line 510 allows the practitioner to see the prismatic deviation value that he is testing.

[0181] Once the practitioner has adjusted the prismatic deviation value around the stop value, he can validate the new value using the validation proposal 550. It is noted that the “new value” can be equal to the stop value. Indeed, the practitioner can test the value just below the stop value, receive as confirmation from the subject that with the just below value, the two images are not aligned, and thus validate that the stop value is the correct value. The value thus validated is recorded as the subject's phoria value.

[0182] The values ​​of the realignment prisms are between the initial value and a final value (which may be lower or higher than the initial value, depending on whether the values ​​of the successive prisms are increasing or decreasing). For example, for a horizontal phoria measurement, the initial value may be 1 A and the final value 20 A. If, with a final prism of 20 A, the subject has not observed any alignment, it is possible to stop the examination and conclude that the horizontal phoria is "> 20 A". For vertical phorias, the maximum value is generally set at 5 A.

[0183] It is noted that the invention applies to any method for determining phoria measurements in which realignment prisms pass in front of the subject. In particular, the invention applies to a novel method for determining a horizontal phoria value described below with reference to [Fig.6].

[0184] It is assumed that an optotype is placed in front of the subject's eyes.

[0185] In a first step 631, the subject's vision is dissociated, similarly to step 231 of [Fig. 2]. In the example described here with reference to [Fig. 6], it is assumed that, in step 631, a top-base prism is placed in front of the subject's right eye. It is noted that, in other embodiments, it is possible to use a bottom-base prism and / or to place the dissociating prism in front of the left eye.

[0186] For example, the prism (called “dissociating prism”) used to dissociate the vision during step 631 may have a value equal to 6 A. Other values ​​are possible, for example values ​​between 3 and 12 A.

[0187] At the end of step 631, the subject therefore sees two images of the target, one below the other. As mentioned above, the two images of the target may be offset (according to the subject's perception) vertically relative to each other (i.e. the images are located on two distinct vertical planes). Unlike the Van Graefe test, in the method of [Fig. 6], the initial realignment prism is selected according to the way in which the subject sees the images of the target, which means that the initial realignment prism is, automatically, more suited to the subject's phoria value. The measurement of the horizontal phoria is thus obtained more quickly.

[0188] Thus, during a step 633, the subject is asked how he sees the two images: vertically aligned or vertically offset and, in this case, which image is to the right (or left) of the other. For example, the practitioner (or a synthesized voice broadcast by a loudspeaker integrated or connected to the control device) can ask the subject the following question: "is the bottom letter to the right, left, or below the top letter?". He can also ask him if the bottom letter is "unstable", that is to say that it oscillates around a position. Such a situation can occur in rather rare cases where the subject brings his fusional convergence into play despite the dissociation of vision.

[0189] If the subject sees the bottom image to the right of the top image, an external base prism having for example a value equal to 0.5 A is placed in front of the subject's left eye (step 6341). As long as the subject does not indicate that the images are aligned vertically (therefore as long as no stop data is sent to the control device), the value of the external base prism is increased. Thus, as long as in step 6342 no stop data is received by the control device, the value of the realignment prism is increased (step 6343). If, during an iteration of step 6342, a stop data is received (which indicates that the subject sees the images aligned vertically), the refractor head stops scrolling the realignment prisms, the current value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0190] If the subject sees the bottom image to the left of the top image, an internal base prism is placed in front of the subject's left eye (step 6351). For example, this internal base prism may have an initial value between 7 A and 13 A. The subject is then asked, in step 6352, how he or she sees the images relative to each other in the vertical plane.

[0191] If the subject sees the two images aligned vertically, the initial value of the internal base realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0192] If the subject sees the bottom image to the right of the top image, the value of the internal base prism is decreased (step 6353).

[0193] By "the value of the prism is decreased (or increased)", it is understood that the refractor head scrolls, in front of the subject's left eye, prisms whose successive values ​​are decreasing (or increasing).

[0194] In step 6354, it is checked whether a stop data item is received, and, as long as this is not the case, the value of the prism is decreased (step 6353). If, at the end of an iteration of step 6354, a stop data item is received by the control device (which indicates that the subject sees the images aligned vertically), the refractor head stops scrolling the realignment prisms, the current value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0195] If the subject sees the bottom image to the left of the top image, the value of the internal base prism is increased (step 6355).

[0196] In step 6356, it is checked whether a stop data item is received, and, as long as this is not the case, the value of the prism is increased (step 6355). If, at the end of an iteration of step 6356, a stop data item is received by the control device (which indicates that the subject sees the images aligned vertically), the refractor head stops scrolling the realignment prisms, the current value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0197] If the subject sees the bottom image unstable, a step 6361 is implemented, during which an internal base prism is placed in front of the subject's left eye. For example, this internal base prism can have an initial value between 3 A and 7 A in distance vision, and between 6 A and 10 A in near vision.

[0198] It is noted that step 6361 may also be implemented when the subject sees the bottom image aligned with the top image. Indeed, in such a situation, one possibility is that the subject does not exhibit horizontal heterophoria. It may, however, be preferable to confirm this by deliberately shifting the image using a realignment prism, then decreasing its value, to confirm the absence of horizontal heterophoria.

[0199] The subject is then asked, at step 6362, how he sees the images relative to each other in the vertical plane.

[0200] If the subject sees the two images aligned vertically, the initial value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0201] If the subject sees the bottom image to the right of the top image, the value of the internal base prism is decreased (step 6363) as long as no stop data is received (step 6364). If, at the end of an iteration of step 6364, a stop data is received (reflecting the fact that the subject sees the images aligned vertically), the refractor head stops scrolling the realignment prisms, the current value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0202] If the subject sees the bottom image to the left of the top image, the value of the internal base prism is increased (step 6365) as long as no stop data is received (step 6366). If, at the end of an iteration of step 6366, a stop data is received (reflecting the fact that the subject sees the images aligned vertically), the refractor head stops scrolling the realignment prisms, the current value of the realignment prism is recorded and corresponds to the stop value defined above (step 639).

[0203] In step 639, the type of heterophoria (exophoria or esophoria) is also determined, based on the type of horizontal prism (internal or external base) which made it possible to obtain the alignment. In the previous example, if the last realignment prism placed is an external base prism, it is an esophoria, and if the last realignment prism placed is an internal base prism, it is an exophoria.

[0204] In steps 6343, 6353, 6355, 6363 and 6365 above, successive realignment prisms may be placed in front of the subject's left eye with a predefined pitch and frequency (e.g. an increase / decrease of 0.5 A or 1 A every second).

[0205] Thanks to the method described above with reference to [Fig.6], the horizontal phoria measurement is obtained more quickly, because the initial information on the vertical shift between the two images without a realignment prism (with only the dissociating prism) is advantageously used to automatically frame the horizontal phoria value. This makes it possible to test a much smaller number of realignment prisms than with a test carried out manually using the conventional method.

[0206] The invention also applies to a new method for determining a vertical phoria value described below with reference to [Fig.7].

[0207] The method for determining a vertical phoria value described below with reference to [Fig.7] can be implemented after determining the horizontal phoria value, regardless of the determination method used to obtain the horizontal phoria value.

[0208] During step 710, the value of the dissociating prism(s) to be placed in front of an eye (or eyes) of the subject is determined, and the dissociating prism(s) are placed in front of the eye (or eyes) of the subject.

[0209] For example, the dissociating prism may be an internal base prism having a value equal to the horizontal phoria value increased by a predetermined amount, for example 3 A. Alternatively, it is possible to associate prism values ​​with predetermined value intervals. When the horizontal phoria value is too large, two internal base dissociating prisms may be placed in front of the subject's eyes (one prism in front of each eye). Optionally, it may also be decided that beyond a certain horizontal phoria value, the vertical phoria value is not determined (in particular for material reasons, because there are no longer any prisms strong enough to dissociate vision).

[0210] For example:

[0211] - If the subject presents esophoria, or if he presents exophoria with a value less than or equal to 7 A, an internal base dissociating prism with a value greater than 8 A in distance vision or greater than 10 A in near vision is placed in front of the subject's left eye;

[0212] - If the subject presents an exophoria with a value strictly greater than 7 A and less than or equal to 12 A, an internal base dissociating prism between 13 A and 18 A in distance vision / between 15 A and 25 A in near vision is placed in front of the subject's left eye;

[0213] - If the subject presents an exophoria with a value strictly greater than 12 A and less than or equal to 20 A, an internal base dissociating prism with a value greater than 18 A is placed in front of the subject's left eye and an internal base dissociating prism between 3 A and 8 A in distance vision / between 5 A and 10 A in near vision is placed in front of the subject's right eye; and

[0214] - If the subject presents an exophoria with a value strictly greater than 20 A, no vertical phoria measurement is performed.

[0215] Of course, the number of intervals above and the values ​​of the limits and prisms are provided as an example and are not limiting.

[0216] At the end of step 710, the subject's vision is dissociated on the horizontal plane (he sees the images on two distinct vertical planes). At step 720, the subject is asked how he sees the images in relation to each other. For example, the practitioner may ask him: "is the letter on the left above, below, or on the same line as the letter on the right?"

[0217] If the subject sees both images on the same line (horizontal alignment), the vertical phoria value is zero (step 730).

[0218] If the subject sees the left image lower than the right one, a prism of The upper base realignment prism is placed in front of the subject's right eye (step 740). For example, this upper base realignment prism has an initial value of 0.5 A. As long as no stop data is received (test 750), i.e., as long as the subject sees the left image lower than the right one, the value of the upper base realignment prism is increased (step 740), for example, by 0.5 A per second. Upon receipt of stop data (test 750) indicating that the subject sees the two images aligned horizontally (i.e., one next to the other, at the same level), the current value of the upper base realignment prism is recorded as the stop value (step 730) and the type of vertical heterophoria is a L / R hyperphoria (left over right).

[0219] If the subject sees the left image higher than the right image, a lower base realignment prism is placed in front of the subject's right eye (step 760). For example, this lower base realignment prism has an initial value of 0.5 A. As long as no stop data is received (test 770), i.e., as long as the subject sees the left image higher than the right image, the value of the lower base realignment prism is increased (step 760), for example by 0.5 A per second. Upon receipt of stop data (test 770) indicating that the subject sees the two images aligned horizontally (i.e., one next to the other, at the same level), the current value of the lower base realignment prism is recorded as the stop value (step 730) and the type of vertical heterophoria is a R / L hyperphoria (right over left).

[0220] As mentioned previously, the invention is not limited to the examples given above with reference to Figures 2, 6 and 7. It can be implemented for any method of determining a phoria value in which realignment prisms having successive increasing or decreasing values ​​are scrolled.

[0221] A general flowchart of the method for determining a phoria measurement according to the invention is shown in [Fig.8]. The method of [Fig.8] is implemented by a control module. In the following, the control module is simply called “module”.

[0222] In a step not shown in [Fig. 8], an optotype is placed in front of the subject's hands. For example, when an instruction to start an examination is received by the control module (via a selection screen for example), the control module can be configured to control a screen to which it is connected, so that it displays the optotype. The placement of the optotype typically takes place before step 810 of [Fig. 8], but it can alternatively be placed after step 810.

[0223] In step 810, the module controls the refractor head to place a dissociating prism in a first location corresponding to a first eye of the subject (for example the right eye). If the method aims to measure a horizontal phoria, the dissociating prism is a vertical prism (e.g., a top-base prism), and if the method is to measure a vertical phoria, the dissociating prism is a horizontal prism (e.g., an inner-base prism). The subject's vision is then dissociated (the subject sees two images of the optotype on two separate horizontal planes or two separate vertical planes).

[0224] Then, during successive steps 820, the module controls the automatic refractor head to scroll realignment prisms in a second location corresponding to a second eye of the subject distinct from the first eye (for example the left eye). The realignment prisms have successive values ​​which follow a predetermined direction of variation, and can therefore be increasing or decreasing (the values ​​of the realignment prism are progressively increased, or the values ​​of the realignment prism are progressively decreased).

[0225] For example, successive values ​​are spaced apart by a predefined step (e.g. 0.5 A or 1 A), and are placed according to a predefined frequency (e.g. every second, every 1.5 seconds, every two seconds, etc.).

[0226] As mentioned above, the module can control the scrolling of the prisms by sending one or more control signals to the automatic refractor head.

[0227] As long as no stop data is received by the control module (test 830), the scrolling of the prisms continues (step 820).

[0228] As soon as a stop data is received by the control module (test 830, arrow “Y”), the module commands the automatic refractor head to stop the scrolling of the realignment prisms (step 835). For example, the control module can send a stop signal to the refractor head (in embodiments where a single control signal is sent to command the scrolling of the realignment prisms), or stop sending control signals to the refractor head (in embodiments where successive control signals are sent by the control module to the refractor head).

[0229] Upon receipt of the stop data, the current value of the realignment prism, i.e. the value of the realignment prism placed in the second location upon receipt of the stop data, is recorded as the so-called stop value (step 840).

[0230] The module controls the display, on the selection screen, of a validation proposal and a set of value proposals as described above (step 845), each value proposal being associated with a respective prismatic deviation value, called selectable value. The selectable values ​​may be values ​​at most a predetermined deviation from the stop value. For example, the selectable values ​​may be included in an interval [VA ± a], where VA is the stop value and a is the predetermined deviation. In other embodiments, the selectable values ​​may be included in the interval [VA - a; VA] if, in step 820, the values ​​of the realignment prisms are increasing, and in the interval [VA; VA + a] if, in step 820, the values ​​of the realignment prisms are decreasing. The stop value VA can be excluded before the first reception of an instruction in step 850, but included during the following iterations (because the user must have the possibility to "return" to the stop value and select it, even if he tests neighboring values).

[0231] It is noted that steps 835, 840 and 845 can be implemented in any order, or in parallel.

[0232] The stop data may be received via the selection screen (e.g., when the practitioner selects a "STOP" button), or via any other means (e.g., via a system comprising a microphone and a voice detection module, when the practitioner or subject says "STOP").

[0233] The module then receives an instruction (step 850) corresponding to a selection of the validation proposal or one of the value proposals.

[0234] If the received instruction corresponds to a selection of the validation proposal, the stop value is recorded as the subject's phoria value (step 870).

[0235] If the received instruction corresponds to a selection of a value proposition, the module controls the refractor head to place a realignment prism whose value corresponds to the value associated with said value proposition in the second location (step 860). The value of the realignment prism placed during step 860 becomes the new stop value. Then the test continues: a new instruction is received (step 850), which corresponds either to a new selectable value or to a validation instruction.

[0236] As long as no validation instruction is received in step 850, the test continues. As soon as an instruction corresponding to a selection of the validation proposal is received in step 850, the new stop value is recorded as the subject's phoria value (step 870).

[0237] The subject's phoria value therefore corresponds to the stop value determined in step 840 if, in the first and only iteration of step 850, the control module receives an instruction corresponding to a selection of the validation proposal, or if during the last iteration of step 850, the control module receives an instruction corresponding to the selection of the "initial" stop value (when the user tests values ​​around the initial stop value but ultimately selects this stop value). Otherwise, the subject's phoria value corresponds to the last selectable value selected in step 850.

[0238] [Fig.9] represents an exemplary system in which a phoria measurement evaluation method according to one or more embodiments of the invention can be implemented.

[0239] The system of [Fig. 9] comprises a control device (or monitoring device) 910 comprising a control module configured to control an automatic refractor head. In the example of [Fig. 9], the control device 910 is connected to a selection screen of a user equipment 940, which is here in the form of a tablet. The selection screen may be a touch screen, by means of which the practitioner can provide the input data to the control device 910. The instructions relating to the measurement of a phoria value may be displayed on the touch screen. Of course, the touch screen may be replaced by other means of selection and receiving instructions, including voice or by input devices such as a joystick or a touch pad.

[0240] The control device 910 is configured to control a display on this selection screen and receive selection data from the selection screen. In this example, the control device 910 has the form of a connection “box” making it possible to link different equipment dedicated to visual examinations. Of course, other embodiments are conceivable. In particular, the control device 910 may comprise the selection screen. In certain embodiments, the selection screen may be replaced by any other system for selecting and receiving instructions (for example a screen and a mouse, or a screen and a voice recognition system).

[0241] The system of [Fig.9] further comprises an automatic refractor head 920 configured to place optical lenses and / or prisms in front of the eyes of a subject. The refractor head 920 comprises two locations corresponding respectively to the two eyes of the subject. The controller 910 is connected to the automatic refractor head 920 and configured to control the placement of lenses or prisms in each location of the automatic refractor head 920.

[0242] The system may also include a display means 930 (e.g., a screen). The control device 910 may be connected to the display means 930 and configured to control a display of data on the selection means 930. For example, the control device 910 may control the display of an optotype on the display means 930.

[0243] The connection between the control device 910 and the automatic refractor head 920 and / or between the control device 910 and the display means 930 and / or between the control device 910 and the user equipment 916 may be wired or wireless.

[0244] [Fig. 10] represents an example of a device 910 making it possible to implement at least certain steps of the method for determining phorias of the invention, according to one or more embodiments of the invention.

[0245] In these embodiments, the device 910 comprises a control module 900, comprising a memory 911 for storing instructions allowing the implementation of the method and temporary data for carrying out different steps of the method described previously.

[0246] The control module 900 further comprises a circuit 912. This circuit 912 may be, for example, a processor capable of interpreting instructions in the form of a computer program, an electronic card whose steps of the method of the invention are described in the silicon, or even a programmable electronic chip such as an FPGA chip (for “Field-Programmable Gate Array” in English).

[0247] The control module 900 comprises an input interface 913 for receiving input data, and an output interface 914 for providing one or more phoria values. The input data may be, for example, measurement start data, instructions corresponding to proposition selections (for example a selection of a validation proposition or a selection of a value proposition).

[0248] The control module 900 may also comprise a communication module 915 configured to communicate with one or more pieces of equipment, in particular the automatic refractor head.

[0249] Of course, the present invention is not limited to the embodiments described above as examples. It extends to other variants.

Claims

Claims

1. A method of determining a phoria value of a subject, the method being implemented by a control module (900) configured to control an automatic refractor head (920) and a selection screen (940), the method comprising: - controlling (810) the automatic refractor head (920) to place, in a first location of the automatic refractor head, a prism called a dissociating prism; - controlling (820) the automatic refractor head (920) to successively place, in a second location of the automatic refractor head distinct from the first location, prisms called realignment prisms, having respective prismatic deviation values distinct two by two, the prismatic deviation values of the successive realignment prisms being increasing or decreasing; - receive (830) a stop data item and, upon receipt of the stop data item: obtaining (840) the prismatic deviation value of the realignment prism upon receipt of the stop data, said value being called the stop value; command (845) the selection screen to display: • a validation proposal (550); and • a set of value propositions (580a, 580b), each value proposition being associated with a respective prismatic deviation value having a deviation from the stop value less than a predefined deviation; - receive (850) at least one instruction corresponding respectively to at least one selection of a value proposition (580a, 580b) from the set of value propositions; - for each instruction received, commanding the refractor head to place (860), in the second location, a realignment prism having a prismatic deviation value corresponding to the prismatic deviation value associated with the value proposition corresponding to said instruction; - receive (850) validation data corresponding to a selection of the validation proposal; - obtaining the prismatic deviation value, called final value, of the realignment prism upon receipt of the validation data; and - determining (870) as the subject's phoria value said final value.

2. A method according to claim 1, wherein the realignment prisms are placed successively with a frequency between 0.5 Hz and 2 Hz.

3. A method according to claim 1 or 2, wherein the prismatic deviation values of successive realignment prisms are spaced apart by a predefined fixed pitch, between 0.5 A and 1 A.

4. Method according to one of the preceding claims, wherein the set of value propositions (580a, 580b) comprises value propositions associated with values which belong to the prismatic deviation values of the successive realignment prisms, wherein the predefined deviation is between 0.5 A and 2 A.

5. Method according to one of the preceding claims, further comprising: - controlling the selection screen to display an advancement line (510) comprising a plurality of positions representing prismatic deviation values; - at each placement of a realignment prism among the successive realignment prisms, controlling the selection screen to display a symbol linked to the prismatic deviation value of the placed realignment prism, the symbol being superimposed on its corresponding position in the advancement line.

6. Method according to the preceding claim, in which each value proposition among the set of value propositions is displayed at the position, in the advancement line (510), corresponding to the prismatic deviation value linked to said value proposition.

7. Method according to the preceding claim, further comprising: - upon receipt of an instruction corresponding to a selection of a value proposition from the set of value propositions, controlling the selection screen to display a representation (590) indicating said value proposition, said representation (590) being displayed at a location distinct from the position, in the advancement line, corresponding to the prismatic deviation value linked to said value proposition.

8. A method according to any preceding claim, wherein the phoria value is a horizontal phoria value, wherein an optotype is placed in front of two eyes of the subject, wherein the dissociating prism is a vertical prism such that the subject sees two images of the optotype respectively located on two separate horizontal planes, the method further comprising: - after having commanded the automatic refractor head to place the dissociating prism in the first location, receiving (633) an initial vertical positioning data comprising: • information indicating whether the subject sees two images of the optotype on the same vertical plane or on two separate vertical planes after placement of the dissociating prism; and • when the subject sees the two images of the optotype on two separate vertical planes, information describing a relative position of the two images of the optotype perceived by the subject; - determine, based on the initial vertical positioning data received, a type of horizontal prism and an initial prismatic deviation value; in which the successive realigning prisms are of the determined horizontal prism type; wherein the respective prismatic deviation values of successive realignment prisms are ordered from the determined initial prismatic deviation value.

9. A method according to the preceding claim, wherein controlling the automatic refractor head to successively place the realignment prisms comprises: - controlling the automatic refractor head to place (6341, 6351, 6361) a first realignment prism having a prismatic deviation value corresponding to the determined initial prismatic deviation value; - receive new vertical positioning data including: • information indicating whether the subject sees the two images of the optotype on the same vertical plane or on two separate vertical planes after placement of the first realignment prism; and • when the subject sees the two images of the optotype on two separate vertical planes after placement of the first realignment prism, information describing a relative position of the two images of the optotype perceived by the subject; - determine, from the new vertical positioning data, whether the prismatic deviation values of the successive realignment prisms are increasing or decreasing.

10. A method according to one of claims 1 to 7, wherein the phoria value is a vertical phoria value, wherein an optotype is placed in front of two eyes of the subject, wherein the realignment prisms are vertical prisms, the method further comprising: - receiving a horizontal heterophoria type and a horizontal phoria value of the subject; - determine, from the received heterophoria type and horizontal phoria value, a horizontal prism type and a horizontal prismatic deviation value; in which the dissociating prism is a prism of the determined horizontal prism type having as prismatic deviation value the determined horizontal prismatic deviation value.

11. Device (910) for determining a phoria value of a subject, configured to control an automatic refractor head (920) and a selection screen (940), the device (910) being configured to: - control (810) the automatic refractor head (920) to place, in a first location of the automatic refractor head, a prism called a dissociating prism; - controlling (820) the automatic refractor head (920) to successively place, in a second location of the automatic refractor head distinct from the first location, prisms called realignment prisms, having respective prismatic deviation values distinct two by two, the prismatic deviation values of the successive realignment prisms being increasing or decreasing; - receive (830) a stop data item and, upon receipt of the stop data item: • obtain (840) the prismatic deviation value of the realignment prism upon receipt of the stop data, said value being called the stop value; • command (845) the selection screen to display: • a validation proposal (550); and • a set of value propositions (580a, 580b), each value proposition being associated with a respective prismatic deviation value having a deviation from the stop value less than a predefined deviation; - receive (850) at least one instruction corresponding respectively to at least one selection of a value proposition (580a, 580b) from the set of value propositions; - for each instruction received, commanding the refractor head to place (860), in the second location, a realignment prism having a prismatic deviation value corresponding to the prismatic deviation value associated with the value proposition corresponding to said instruction; - receive (850) validation data corresponding to a selection of the validation proposal; - obtaining the prismatic deviation value, called final value, of the realignment prism upon receipt of the validation data; and - determining (870) as the subject's phoria value said final value.

12. A system for determining a phoria value of a subject comprising a device according to claim 11, an automatic refractor head and a selection screen.

13. Computer program product comprising instructions for implementing the method according to one of claims 1 to 10 when this program is executed by a processor.

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