Devices and methods for detecting tear film breakup

Abstract

An apparatus and method for detecting tear film breakage, comprising: a backlit translucent plate having a test pattern (10) positioned in front of at least one eye (101) of a patient (100) and having a pattern reflected on the patient's eye; and at least one digital camera (21, 22) connected to a computing system (30) having components for processing and analyzing images, the lens of the camera being pointed at the patient's eye to capture the reflection of the test pattern (10) on the patient's eye, wherein the test pattern (10) has a series of lines in the form of alternating horizontal or vertical transparent and opaque lines (12) forming the pattern and at least one opening facing the camera lens.

Description

Technical Field

[0001] This invention relates to the field of dry eye syndrome detection. Background Technology

[0002] Tests used to assess dry eye syndrome include those in which a physician uses fluorescein and directly observes changes in the patient's tear film. This so-called invasive test typically measures the time it takes for the first tear film breakup to occur.

[0003] There are also non-invasive tests that measure non-invasive breakup time. This test assesses tear film quality, allows determination of the time between eyelid blink and tear film breakup, and uses the reflection from a test chart from the cornea, which has a pattern consisting of concentric circles and radial lines.

[0004] When the membrane ruptures, the lines and / or circles of the reflected pattern become deformed or areas of the reflected pattern are lost.

[0005] Images of the reflected pattern are acquired sequentially by a camera and processed by a computerized processing system that analyzes changes in the pattern over time to detect deformation of the pattern and infer the timing of the membrane rupture.

[0006] Currently available devices typically use a pattern consisting of concentric circles and radial lines. This causes several problems:

[0007] Due to the shape of the test map and the extent to which the cornea is covered by the disk segment, the spatial resolution at the edge of the field of view is inherently worse than the spatial resolution at its center.

[0008] At the center of the field of view where radial lines converge, it is difficult to determine the deformation of the pattern.

[0009] To increase spatial resolution, the density of the pattern in the test image must be increased. Furthermore, the algorithms used to detect circle deformation (which require finding the most probable circle in the image), determining whether a point in the image belongs to a possible circle to be evaluated, and calculating the distance from a given point to the circle it should belong to are all complex, and the processing and computation time required to detect broken regions based on the image is considerable.

[0010] Therefore, it will be clear that, on the one hand, devices using conventional patterns of concentric circles and radial lines suffer from a lack of spatial resolution uniformity, and on the other hand, increasing the resolution at the edges of the field of view will have an adverse effect on computation time.

[0011] Due to the low resolution of this method, measurements can produce inaccurate and overestimated fracture times.

[0012] Technical issues

[0013] Therefore, there is real uncertainty regarding whether tear film rupture has occurred. Furthermore, the algorithms used to detect circular deformation (which require finding the most probable circle in the image), determining whether a point in the image belongs to a possible circle to be evaluated, and the distance from a given point to the circle it should belong to are all complex, and the processing and computation time required to detect rupture regions based on images is considerable. Moreover, as seen above, the measurement accuracy is low, and machines using this principle are not sensitive enough to measure small ruptures, especially since the resolution decreases with distance from the center of the pattern composed of circles and radial lines. However, physicians require reliable and reproducible measurements for diagnosis. Summary of the Invention

[0014] The present invention improves upon this situation and firstly specifies the use of a device comprising a pattern consisting of bright and dark lines, and the observation of the reflection of this pattern from the cornea.

[0015] Therefore, according to one aspect, the present invention provides an apparatus for detecting one or more tear film breaks, comprising: a backlit translucent plate equipped with a test pattern positioned in front of at least one eye of a patient and having a pattern reflected from the patient's eye; and at least one digital camera connected to a computing system, the computing system being internal or external to the measuring device and having components for processing and analyzing images, the objective lens of the camera being pointed at the patient's eye to capture a reflection of the pattern of the test pattern from the patient's eye, wherein the test pattern has a series of lines in the form of alternating horizontal or vertical transparent and opaque lines constituting the pattern and at least one aperture facing the objective lens of the camera, and wherein the transparent lines form bright lines reflected from the patient's eye on the backlit translucent plate, while the opaque lines are reflected as dark lines, the components for processing and analyzing images being configured to detect deformation of the bright or dark lines of the pattern of the test pattern reflected from the patient's eye and identify tear film breaks revealed by these deformations.

[0016] The device of the present invention is based on a device that detects bright or dark lines by alternating between bright and dark lines. It avoids the problems of devices that use test patterns with circular patterns and allows for precise detection of membrane ruptures, even though at first glance it may seem incongruous with the spherical curvature of the eye.

[0017] Furthermore, because the resolution of the pattern remains uniform across the entire measured area, the present invention allows for a series of measurements to track the progression of tear film breakup.

[0018] The device features described in the following paragraphs may be implemented optionally. These features may be implemented independently of each other or in combination with each other:

[0019] The lines in the series are preferably parallel lines.

[0020] The width of the line advantageously increases from the center line of the test pattern toward the edge of the test pattern.

[0021] The test diagram has a cylindrical curvature generated using a vertical generatrix.

[0022] The test map is advantageously large enough to produce an image on most of the cornea of ​​one or more of the patient's eyes; for example, it is designed to fill most of the human field of vision.

[0023] The components for processing and analyzing images may advantageously include components for converting the images into grayscale.

[0024] Components used for processing and analyzing images may advantageously include anisotropic bandpass filtering components.

[0025] The components for processing and analyzing images may advantageously include components for analyzing images in consecutive pixels in a direction perpendicular to the line, components for searching for bright or dark segments in consecutive pixels, and components for quantizing the size of bright or dark segments and for removing segments whose size is incompatible with the image of the line of the pattern.

[0026] The components for processing and analyzing images may advantageously include components for marking / classifying bright or dark segments of targets, said components being adapted to reconstruct a first target corresponding to the length of a bright or dark line of a pattern and to remove a second target with a shape incompatible with said bright or dark line.

[0027] The components for processing and analyzing images may advantageously include components for joining the lengths of bright or dark lines on the same axis, components for calculating a polynomial regression on the bright or dark line data to calculate an RMS curve representing the edge of the line, and computational components for detecting the tear film breakage region for image points at the edge of the line, the distance from the line edge to the curve being greater than a given tolerance value.

[0028] According to another aspect of this patent application, which can be used independently of the test diagrams described above, the device may include components for tracking one or more of the patient's eyes based on iris recognition and tracking.

[0029] Here, these components allow for comparison of detected tear film breakage with the analyzed eye, but can also be used in other situations where iris tracking is required.

[0030] According to a particular aspect of the device of this patent application, the backlit translucent plate carrying the test pattern and one or more cameras are integrated into an ophthalmic measurement device, such as an ophthalmic structure equipped with a support on which the patient's head rests, or integrated into a headset worn by the patient.

[0031] This patent application further relates to a method for detecting tear film breakage by means of, for example, the apparatus described above, and includes detecting an eyelid blink at a transmission start time and performing at least one sequence, said at least one sequence including continuously capturing images from said start time to the next eyelid blink and calculating the area of ​​breakage.

[0032] The method features described in the following paragraphs may be implemented optionally. These features may be implemented independently of each other or in combination with each other:

[0033] The method may include capturing images every 0.2 to 0.5 seconds, and preferably every 0.3 seconds.

[0034] The method advantageously includes a series of processing and analysis steps for each captured image, the processing and analysis steps including:

[0035] - Convert the image to grayscale;

[0036] - The converted image is filtered by means of an anisotropic bandpass filter in order to reduce vignetting and increase the uniformity of the image brightness;

[0037] - The steps of searching column by column for bright or dark segments in the image, quantifying the size of the bright or dark segments, and removing segments whose size is incompatible with the correspondence between the lines of the pattern;

[0038] - The steps of marking / classifying bright or dark segments of targets, reconstructing the first of the targets corresponding to the length of the line forming the pattern, and removing the second of the targets with shapes incompatible with the line of the pattern;

[0039] - The steps of joining the lengths of lines at the same level, and the steps of calculating a polynomial regression on the line data in order to calculate the RMS curve of the line edge;

[0040] - The tear film breakage area is calculated by measuring the distance from a point on the edge of the line to the curve, the breakage area corresponding to the edge of the line, the distance from the edge of the line to the curve being greater than a given tolerance value.

[0041] In this method, anisotropic filtering and polynomial regression are image processing components that together ensure fast image processing and good detection of defects caused by tear film breakage.

[0042] According to one aspect of this patent application, which can be used in another method, the method includes the step of tracking one or more eyes of the patient by means of an iris tracking method. Here, these steps allow for the repositioning of the detected tear film breakage area relative to the analyzed eye.

[0043] Eye-tracking steps may include:

[0044] - The image is transformed in the first instant by an anisotropic bandpass filter applied in the width direction of the eye to produce a pair of transitions from dark to bright and from bright to dark along the horizontal axis of the eye.

[0045] - Segment the image to identify rising and falling transition pairs that form segments that necessarily represent bright areas in the image;

[0046] - The image is filtered to remove light fragments from the central region of the pattern as well as the top and bottom regions of the image;

[0047] - Considering light segments, other areas of the image are no longer considered in this analysis, and the RMS circle of the periphery of the iris is calculated at the first moment based on the right end of the light segment on the left side of the image and the left end of the light segment on the right side of the image;

[0048] - The step of removing points that are too far from the RMS circle; and

[0049] - Regarding the remaining points, a new step is to calculate the RMS circle (93) to fit the outline of the iris.

[0050] This patent application further provides a computer program including instructions for implementing a method for detecting ruptures and an eye-tracking method when the program is executed by a processor.

[0051] This program may be stored on a computer-readable non-volatile storage medium, on which a program for implementing the method is stored when the program is executed by a processor.

[0052] This patent application concludes with a test pattern for implementing the device of the invention, the test pattern being generated by means of a transparent polymer film having opaque lines printed or screen-printed on the film, the transparent polymer film including at least one hole surrounded by an opaque border in the central region of the test pattern, the film being designed to be positioned on a backlight translucent plate of the device. Attached Figure Description

[0053] Other features, details, and advantages of the invention will become apparent after reading the following detailed description and analyzing the accompanying drawings, in which:

[0054] [ Figure 1 [This is a planar front view of a test pattern having the pattern of the present invention;]

[0055] [ Figure 2[This is a schematic diagram of the device described in this patent application;]

[0056] [ Figure 3 This invention demonstrates a first example of a measuring device that can be used in the context of this patent application;

[0057] [ Figure 4 [Image of the patient's eyes after the first treatment step;]

[0058] [ Figure 5A ]、[ Figure 5B ]、[ Figure 5C ]、[ Figure 5D ]and[ Figure 5E Display processing Figure 4 Various stages of the image of the eye;

[0059] [ Figure 6A ]and[ Figure 6B ]exhibit Figure 5E Details;

[0060] [ Figure 7 Displayed after image analysis Figure 4 Images of eyes;

[0061] [ Figure 8 [Shows an image of the patient's eyes as they look at the camera;]

[0062] [ Figure 9A ]、[ Figure 9B ]and[ Figure 9C The display is determined according to one aspect of this patent application. Figure 8 The steps for determining the position of the iris of the eye;

[0063] [ Figure 10 [Shows images of the patient's eyes when their gaze is off-camera;]

[0064] [ Figure 11A ]、[ Figure 11B ]and[ Figure 11C The display is determined according to one aspect of this patent application. Figure 10 The steps for determining the position of the iris of the eye;

[0065] [ Figure 12 This schematically illustrates a method for detecting areas of tear film breakage.

[0066] [ Figure 13 This schematically illustrates a method for repositioning the area of ​​tear film breakup within a reference frame attached to the eye. Detailed Implementation

[0067] The drawings and the following description illustrate one or more instances of the embodiments, which may therefore serve not only to better understand the subject matter of this patent application, but also, where appropriate, to facilitate its definition.

[0068] The method and apparatus for detecting tear film breakage according to this patent application use a test produced from a transparent polymer film. Figure 10 (shown in) Figure 1 (In the context of the image), the transparent polymer film includes a pattern 11 consisting of alternating straight and parallel lines 12, 13. The pattern includes opaque lines 12, such as black lines separated by transparent lines 13, which allow light from a light source to pass through a translucent carrier behind the pattern to create bright lines that are reflected from one or more of the patient's eyes.

[0069] In this example, the test Figure 10 The pattern 11 comprises twelve opaque lines 12, excluding the top and bottom boundaries of the test pattern. These opaque lines are separated by transparent lines 13 and centered on a semi-transparent center line. The test pattern can be mounted on a plastic frame for easier handling.

[0070] By convention, the axis parallel to the axis passing through the patient's eye will be called the horizontal axis, and the axis perpendicular to this axis will be called the vertical axis; in the example shown, the lines of the pattern are horizontal.

[0071] like Figure 2 The test shown in the figure is performed on its plastic carrier 10b. Figure 10 Positioned on a translucent carrier 10a, the translucent carrier itself has holes drilled for a camera objective lens to pass through, and the device uses a diffuse light source 23 behind the carrier of the pattern to illuminate the pattern. The reflection of the pattern is observed by one or two digital cameras, and two digital cameras 21 and 22 are provided for observing both eyes.

[0072] For example, diffuse light source 23 can be generated by means of an integrated box or sphere or something similar to an LCD backlight.

[0073] The test image has two empty regions 14, centered on an opaque border 15 along a horizontal midline. These empty regions are spaced apart by a distance corresponding to the average interpupillary distance, such as... Figure 1 As shown in the image. Return to Figure 2 The camera is positioned behind the empty area and in front of the patient's eye 101. The camera's objective lens takes a picture or photograph of the patient's eye through the empty area. If the optical properties and cleanliness of the substrate of the test pattern are compatible with image formation (transparency and non-scattering), then the empty area can be replaced by a transparent substrate area of ​​the test pattern.

[0074] The camera is, for example, a CMOS camera with a 1 / 4" sensor. According to the non-limiting example shown, the transparent area is a circular aperture with a diameter suitable for the camera objective lens. For a camera with an optics focal length of approximately 4mm, an aperture of approximately 14mm is provided, and the opaque border is an opaque square of approximately 16mm × 16mm. The goal of these borders is to terminate precisely upstream of the aperture that receives the camera objective lens.

[0075] In this example of the embodiment, one or more cameras transmit images with a resolution of 1920×1080, which is sufficient to obtain analysis of membrane rupture without unduly increasing the computational load on the system.

[0076] The video signal or camera signal is sent to a computerized processing device 30 or computing system, which is inside or outside the measuring device, and to avoid duplication of this processing device, the video signals of the two cameras are transmitted on the circuit board 24 of the device via a multiplexer that allows either of the video channels to be sent to the processing device 30 as needed.

[0077] The camera photographs or captures an image of the patterned lines reflected from the patient's cornea. Since the cornea can be largely considered a spherical refractive interface, it has high field curvature and the image exhibits significant distortion. To at least partially compensate for this distortion and ensure that the line width remains almost constant from the central axis of the pattern to the edge of the image in the captured image, the pattern of the test chart includes lines whose period increases from the central axis of the pattern to the edge parallel to the carrier of the line. For example, the central white line may have a height of approximately 2.8 mm, the adjacent black lines a height of 2.2 mm, and the final white line a height of 3.8 mm, with the black lines preceding these white lines having a height of 2.8 mm. This process is optimized to compensate for the curvature of a standard eye. In the described method, bright lines are used to locate the tear area. The number and width of the bright lines may differ from a given example but are chosen to obtain sufficient clarity for meaningful detection of the membrane tear area given the resolution of one or more cameras.

[0078] In the context of this patent application, white lines are reflected and displayed by the corneal refractive interface, while they are backscattered from the bulbar conjunctiva and iris of the eye. In contrast, the alternation of dark and bright lines forms a continuous background, the brightness of which depends on the ratio between the transparent area of ​​the test pattern and its total area.

[0079] exist Figure 2 In the middle, the test pattern seen from above is bent around the vertical axis to form part of a cylinder and conforms to the curvature of the patient's head by 100 degrees, so that the image of the test pattern covers most of the cornea.

[0080] The reason is:

[0081] a. Optical conjugation:

[0082] The camera sees the test image reflected from the cornea, which is roughly considered as a spherical mirror with a radius of about 8 mm or a focal length of 4 mm. Given this short focal length, the test image (the target in the optical conjugate) must be large enough that the image reflected from the cornea is large enough to be comparable in size to the outer diameter of the iris. This determines the size of the mask.

[0083] b. Photometric measurement:

[0084] For the test image to be visible, bright lines from the extreme edges of the test image must enter the pupil of the objective lens. Because the cornea is a highly curved mirror, it is necessary to graze the bright lines reaching the cornea at the edge of the field of view.

[0085] This proves that the curvature of the test graph is reasonable.

[0086] exist Figure 3 In this structure, the measuring device is mounted on an ophthalmic structure with a mandible and forehead support, the structure including a column 44 and a housing 43, with a camera integrated in the housing and the housing receiving the test on a forward-curving surface. Figure 10 The patient is positioned in front of the forward-curved face, with their chin resting against the support 45. With this configuration, for a 4mm focal length camera, the distance between the patient's eye and the test image is approximately 50mm. The measuring device can also be integrated into a headset worn by the patient.

[0087] The position of the eyes relative to the camera is allowed to change (different eye distances from one person to the next), and the focal length and distance are selected to allow the entire eye to be seen. Next, a window of focus centered on the patient's pupil is selected via operator actions, with the operator marking the center of the pupil in the image.

[0088] Therefore, the lines of the test chart are very clear in the image, and the focus is adjusted using the thumb wheel 42.

[0089] The objective of the measurement method in this patent application is to detect and measure the development of dry eye areas and tear film breakage areas. The measurement method includes repeatedly capturing images of one or both eyes of the patient at a repetition rate of approximately 0.2 to 0.5 seconds, and practically 0.3 seconds, after one or more eyes blink.

[0090] The method is primarily described in the case of a test pattern consisting of horizontal lines extending along an axis passing through the patient's two pupils, but is adjustable, particularly by means of components for processing a series of pixels and a 90° rotation of the anisotropic bandpass filter described below. Furthermore, the method described in the case of detecting bright lines is applicable to detecting dark lines.

[0091] In the computing system 30, the measurement step includes an image processing step that begins with capturing a raw image of the patient's eye, which includes:

[0092] - Convert the image ( Figure 12 Step 205) converts it to grayscale. Figure 4 An example illustrating the results is shown in image 51, which depicts a pattern on the iris 50, with an image of border 52 surrounding the camera objective. In this image, and in the original color image, the shape of the reflected bright lines includes localized defects (especially irregular line edges that individually suggest tear film deformation);

[0093] - Second step ( Figure 12 Step 210) includes applying an anisotropic bandpass filter, which is applied in a direction perpendicular to the direction of the reflected line, i.e., in the vertical direction, and thus applied to the pixel column of the image. In the case of a test pattern consisting of horizontal lines or a test pattern consisting of vertical lines, the image is rotated 90° in the latter case to obtain bright lines oriented in the horizontal direction, and the filter is configured to remove or attenuate modulation of low and high spatial frequencies in the vertical direction by abrupt transitions between gray levels. Figure 5A The image output from the filter is shown in the image. This filter is particularly advantageous in removing vignetting and defects in illumination uniformity. This transformation emphasizes the edges of the eyelid 53, the bright lines 54 of the test pattern, and preserves the image of the border 55.

[0094] Next, also in the case of bright lines oriented in the horizontal direction, the method includes analyzing the image in a 220-pixel column, such as... Figure 12 As shown in the image, a method is used to search for bright vertical segments. The resulting image then includes, for example,... Figure 5B Lines 56, 57, 58, and 59 are shown in the diagram. Once this analysis has been performed, the bright segments are checked in steps 230 and 235 based on their size. For example, as with segments that form the outline of the eyelid, this allows for the removal of segments that are too large or too short and do not clearly correspond to the pattern lines. Figure 5C The image at the end of this step is displayed, retaining the column segments of independent line 61, the image lines of pattern 62, the background 64, and the border 63. Note that the eyelashes cause the line 65 at the top of the image to split considerably. In the case of a test image composed of vertical lines, the segments are analyzed and checked pixel by pixel.

[0095] When segmentation is complete, the processing method includes an algorithm for labeling / classifying 240, 250, and 260 bright segments to obtain targets representing the bright length of the pattern line and discarding bright targets that do not have the desired shape, which are therefore considered artifacts. This algorithm first joins adjacent column segments to reconstruct the horizontal length. The results of this labeling / classification are shown in... Figure 5DIn this section, each line found has been assigned a color, represented here in grayscale. This classification allows the creation of complete lines 70 or individual lines of lengths 71 and 72.

[0096] In a subsequent step, the lengths of bright lines at the same level (e.g., with similar width and altitude) in the 280 image are combined, and then polynomial regression 285 using a polynomial of order greater than two is applied to calculate the RMS curve of the line edge shape. This step is shown in Figure 5E In this figure, special attention will be paid to the lengths 73a and 73b of the lines dividing the image by the frame surrounding the camera objective, and the lengths 73c and 73d of the bottom lines, which are joined by the RMS curves of the top 74 and bottom 74'. (Magnification) Figure 6A This allows for a clearer view of the RMS curves 74 and 74' between lengths 73c and 73d at the bottom of the image. Next, two criteria are used to detect the location or region of membrane rupture in the areas where the line edges include measurement points deviating from the shape given by the polynomial:

[0097] - The deviation from the polynomial is greater than the threshold.

[0098] - There are multiple adjacent columns that exceed this threshold.

[0099] This is for example in Figure 6B The area shown in the diagram is the region 76 where the edge 77b of line 77a does not conform to curve 74'.

[0100] As seen above, the method can be based on the processing of dark lines. Grouping the transition pairs (ascending and descending transitions in the case of bright lines) allows checking the consistency of the width of the obtained segments and allows discarding segments that are too wide or too narrow to form a test plot. Once the length has been determined, a polynomial regression is performed on each side of the length: one polynomial for ascending transitions and one polynomial for descending transitions. Therefore, the method of the present invention makes it possible to obtain the same polynomial regression and the same final result with equally good targeting of dark segments and dark lines.

[0101] The measurement results in a map of the location of tear film breakup, for example... Figure 7 As shown in the image, the image of the fracture point 78 has been positioned on the initial color image of the eye, which is shown in grayscale here.

[0102] As seen above, images are captured at approximately 0.3 seconds. The start time is defined by the blink of the eyelid, and repeated measurements for each image within a certain time period allow for the construction of fragmented images that change over time.

[0103] One issue to consider is that the patient's line of sight can change direction during the image acquisition cycle.

[0104] Because the camera observes the reflection of the pattern from the cornea, which roughly resembles a spherical refractive interface, the position of the pattern's image remains almost constant in the image transmitted by the camera, whereas the position of the iris changes when the patient moves their eyes. Therefore, a given point in the test pattern's image is not connected to a fixed point on the cornea, but rather to a point that depends on the direction of gaze. This means that measurements must be taken with reference to the position of the observed eye, rather than to the image of the pattern.

[0105] Therefore, the position of the eye in each image must be tracked. Preferably, the outline of the iris of the eye is fitted, because it forms a high contrast with the bulbar conjunctiva, which is lighter in color and from which the test image is not reflected. The pupil is easier to fit due to the reflection of the test image, which complicates the image analysis.

[0106] The following method can be implemented, either within the context of this patent application or independently, to perform other measurements on the eye. Furthermore, this method is independent of the orientation of the lines on the test chart.

[0107] Figure 8 , 9A 9B and 9C correspond to the processing operations performed on the image of the patient's eye viewed by the camera, and Figure 10 , 11A 11B and 11C correspond to the processing operations performed on images of the patient's eyes whose gaze has deviated from the camera.

[0108] exist Figure 8 In the image 83, the eyes 80 are looking straight ahead, and the image of the pattern 83 is centered relative to the iris 82, which itself is centered relative to the eyelid 81.

[0109] Figure 13 The image processing method for locating the iris is illustrated schematically. It includes a first transformation of the image via the application of an anisotropic bandpass filter 400, which is applied horizontally to detect brightness transitions along a horizontal axis. In this operation, it is desirable to distinguish between descending transitions (light to dark) and ascending transitions (dark to light), and for clarity, [the image processing method is described]. Figure 9A In the grayscale image, the dark crescent shape 84 represents the light-to-dark transition (falling transition), and has been... Figure 9A The light crescent shape 85 represents the transition from dark to light (ascending transition). In images where a significant transition does not exist, such as crescent shape 86, the image becomes an average grayscale, and the outline of the iris is represented by a ring portion 87 located immediately adjacent to the light-to-dark transition on the left-hand side and immediately adjacent to the dark-to-light transition on the other side of the eye.

[0110] Return to Figure 13The second operation involves segmenting image 410 to identify the boundaries that form bright areas in the image, particularly the rising and falling transition pairs around the bulbar conjunctiva (e.g., Figure 9A (84, 85). Figure 9B These transition pairs are indicated by boundaries 88, 89 and 90, 91, and border region 92 potentially defines the bulbar conjunctiva.

[0111] After this transformation, the method includes, for example: Figure 13 The image is filtered 420 as shown, which removes the central region of the pattern as well as the top and bottom regions of the image. Based on the remaining portion, an RMS circle 430 is calculated for the periphery of the iris from the right end of the left-hand segment of the image and from the left end of the right-hand segment of the image. For this calculation, points that are too far from the RMS circle, corresponding to defects particularly caused by eyelashes or eyelids, are discarded in step 440, and with respect to the remaining points, a new RMS circle 93 is calculated to fit the contour of the iris. Figure 9C The image is displayed on the original image of the eye.

[0112] Figure 10 The eye 80' is shown looking to the side, with its iris 82' offset relative to the pattern 83'. For this position of the eye, in... Figure 11A In the middle, the transitions 84' and 85' around the dark areas 86' and 87' corresponding to uniform color are laterally offset, but... Figure 11B The visible arcs 89' and 90' corresponding to the edges of the iris remain detectable. The application of the tracking method again allows for the regeneration of the RMS circle 93', which will, as... Figure 11C The tear film break is then repositioned within the original image shown. Depending on the position of the circle defining the iris's contour, the detected tear film break is then repositioned in step 450. This makes it possible to anchor the tear film break to the contour of the eye, rather than to the image itself.

[0113] Preferably, this sequence is performed for each image after the analysis of the line patterns described above.

[0114] As stated above, this method is used here to relocate the ruptured area, but it can also be used for other types of detection and methods that require tracking the eye's position.

[0115] According to one aspect of this patent application, the apparatus may include a manual trigger that provides the apparatus, subsequently triggering an image capture sequence upon the occurrence of an event such as a series of two blinks of a patient's eyelid. For this purpose, the system includes a method for recognizing eyelid blinks, which allows the measurement sequence to be started automatically. Similarly, the system may automatically stop the measurement sequence upon detecting a subsequent blink of the eyelid, or automatically stop the sequence after, for example, a 15-second time delay.

[0116] For example, an image capture sequence may include 30 to 50 images, and in the case of an image capture sequence of 15 seconds in length with images captured every 0.3 seconds, the sequence includes 45 images. Images can be analyzed after the image capture sequence, and due to the selected solution, i.e., the option used to work on patterns composed of lines, the processing time remains low, for example, 15 seconds using a standard computer.

[0117] Once the measurements are complete, the physician will have, on the one hand, a spatial and temporal map of tear film breakup on the corneal surface, and on the other hand, a time-related curve tracking the occurrence of tear film breakup over time. This time-related curve, and especially its slope, will reveal the frequency of breakup in the tear film. This allows for optimized interpretation of the performed examination.

[0118] This invention is not limited to the examples described above, which are merely illustrative, but covers any variations within the claimed scope, such as any other distribution or variation of line height that can be conceived by one of skill in the art. Specifically, as stated above, the pattern lines that are parallel horizontal lines in the illustrated examples can be replaced by vertical lines, and image rotation, for example, allows image processing components used to detect line deformation to be applied to this configuration without changing their orientation.

Claims

1. A device for detecting one or more tears, comprising: A backlit translucent plate (10a) with a diffuse light source (23) disposed behind it, the backlit translucent plate being equipped with a test pattern (10) positioned in front of at least one eye (101) of a patient (100), the test pattern having a pattern (11) illuminated by the diffuse light source and the pattern being reflected from the patient's eye; and at least one digital camera (21) connected to a computing system (30) having components for processing and analyzing images, the objective lens of the digital camera being pointed at the patient's eye to capture the reflection of the pattern (11) of the test pattern (10) from the patient's eye, wherein the pattern of the test pattern (10) has a series of lines in the form of alternating horizontal or vertical transparent parallel lines (13) and opaque lines (12), the backlight forming a horizontal or vertical line on the eye through the translucent plate. Vertical bright and dark lines, wherein components for processing and analyzing the image are configured to detect deformations of the horizontal or vertical bright or dark lines reflected from the patient's eye and identify tear film breakage revealed by these deformations, and wherein the components for processing and analyzing the image include components for analyzing the image in consecutive pixels in a direction perpendicular to the line, components for searching for bright or dark segments in consecutive pixels, components for quantifying the size of the bright or dark segments, and components for removing segments whose size is incompatible with the image of the line in the series of lines of the pattern reflected from the patient's eye, and wherein the components for processing and analyzing the image include components for marking / classifying bright or dark segments of targets, adapted to reconstruct a first target corresponding to the length of the bright or dark line reflected from the patient's eye and adapted to remove a second target with a shape incompatible with the bright or dark line.

2. The apparatus according to claim 1, characterized in that, The width of the line increases from the center line of the test pattern toward the edge of the test pattern.

3. The apparatus according to any one of the preceding claims, characterized in that, The test diagram (10) has a cylindrical curvature generated using a vertical generatrix, such that it forms part of a cylinder and conforms to the curvature of the patient's (100) head.

4. The apparatus according to claim 1, characterized in that, The components for processing and analyzing images include components for converting the images into grayscale.

5. The apparatus according to claim 1, characterized in that, Components used for processing and analyzing images include anisotropic bandpass filtering components.

6. The apparatus according to claim 1, characterized in that, The components for processing and analyzing images include components for joining the lengths of bright or dark lines on the same axis, components for calculating a polynomial regression on the bright or dark line data to calculate an RMS curve representing the edge of the line, and computational components for detecting the tear film breakage region for image points at the line edge, the distance from the line edge to the curve being greater than a given tolerance value.

7. The device of claim 1, comprising a component for tracking the patient’s eyes based on iris recognition and tracking in order to compare detected tear film breakage with one or more analyzed eyes.

8. The apparatus according to claim 1, characterized in that, One or more of the backlit translucent plate (10a) carrying the test diagram (10) and the digital camera (21) are integrated into the ophthalmic measurement device.

9. A method for detecting tear film breakage by means of the apparatus of claim 1, comprising detecting an eyelid blink with a transmission start time and performing at least one sequence, said at least one sequence comprising continuously capturing images from said start time to the next eyelid blink and calculating the breakage region, the method comprising: - Capture (200) images every 0.2 to 0.5 seconds. - For each captured image, a series of processing and analysis steps are included, which include: a. Convert the image to grayscale (205); b. The converted image is filtered (210) by means of an anisotropic bandpass filter in order to reduce vignetting and increase the uniformity of brightness of the image; c. The steps of searching column by column for bright or dark segments in the image (220), quantifying the size of the bright or dark segments, and removing segments whose size is incompatible with the correspondence between the lines of the pattern; d. The steps of marking / classifying bright or dark segments of targets, reconstructing the first of the targets corresponding to the length of the lines forming the pattern, and removing the second of the targets with shapes incompatible with the lines of the pattern; e. The steps of joining the lengths of lines at the same level, and the steps of calculating the RMS curve of the line edge using polynomial regression on the line data; f. The tear film breakage area is calculated by measuring the distance from a point on the line edge to the curve, the breakage area corresponding to the line edge, the distance from the line edge to the curve being greater than a given tolerance value.

10. The method for detecting tear film breakup according to claim 9, characterized in that, Capture 200 images every 0.3 seconds.

11. The method for detecting tear film breakage according to claim 9, comprising the step of tracking one or more eyes of the patient by means of an iris tracking method to reposition the area of ​​tear film breakage detected relative to the analyzed eye of the patient.

12. The method according to claim 11, characterized in that, Eye-tracking steps include: - The first step is to transform the image by means of an anisotropic bandpass filter applied in the width direction of the eye to produce a pair of transitions from dark to light and from light to dark along the horizontal axis of the eye. The step involves segmenting the image to identify rising and falling transition pairs that necessarily represent bright areas in the image. - A step, which is image filtering, removes light fragments from the central region of the pattern as well as the top and bottom regions of the image; - Step, which is to consider light segments, in this analysis other areas of the image are no longer considered, and the RMS circle of the periphery of the iris is calculated at the first time based on the right end of the light segment on the left side of the image and the left end of the light segment on the right side of the image; - The step is to remove points that are too far from the RMS circle; and - Regarding the remaining points, a new step is to calculate the RMS circle (93) to fit the outline of the iris.

13. A computer-readable non-volatile storage medium having thereon stored a program for implementing the method of claim 9 when the program is executed by a processor.

14. A test diagram (10) for implementing the apparatus according to claim 1, characterized in that, It is produced by means of a transparent polymer film having opaque lines (12) printed or screen-printed on the film and separated by transparent lines, the film being designed to be positioned on the backlight translucent plate (10a) of the device.

15. The test pattern according to claim 14, comprising at least one empty region (14) surrounded by an opaque border (15) or at least one transparent substrate region in the central region of the test pattern.

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