Method for optimizing implant power calculation formulas

Abstract

Device and method for characterizing an eye-implant system. This method characterizes a target system comprising a target implant and a target eye, said target system being characterized by an optical performance (CP) and a power (P) of said target implant.It comprises the following steps: - obtaining (E10) an optical property adjustment value (C1), intended to adjust at least one adjustable optical property (PA) of said target system (SC), - obtaining (E20) an optical performance adjustment value (C2) of said target system; - determining (E30, E30') a correspondence between said power (P) and the optical performance (CP) from at least one optical property (PO) of the target system, at least one of which is adjustable (PA), said optical property adjustment value (C1) and said performance adjustment value (C2), the determination (E30) comprising the steps: (i) adjusting (E30A) a value of said adjustable property (PA) with said optical property adjustment value (C1), (ii) adjusting (E30B) a value of said optical performance (CP) or said power (P) with said performance adjustment value (C2). Figure for abstract: Fig.6.

Description

Title of the invention: Method for optimizing implant power calculation formulas Background of the invention

[0001] The invention lies in the field of ocular implants.

[0002] Cataract surgery involves replacing the lens with an artificial implant. The properties of this artificial implant must be determined before the operation to meet the objective of refractive correction of the operated eye. This characterization of the implant requires determining its power, expressed in diopters.

[0003] This determination includes in particular a step of predicting a postoperative property of the eye and the implant, for example the expected position of the implant after its stabilization in the eye.

[0004] A predicted power calculated on the basis of such a poorly estimated postoperative property may result in an effective correction of the operated eye relatively far from the refractive correction objective.

[0005] The difference between the effective refractive correction after surgery and the desired refractive correction before surgery will be called a “performance error”.

[0006] It has been proposed, in the publication https: / / www.karger.eom / Article / Pdf / 514916, to optimize the prediction of the power of an implant by adjusting the predicted position of this implant by taking into account adjustment constants in the calculation of this position, so as to cancel a bias in the prediction of the refractive correction or to minimize an error on this same prediction, for example the mean square error or the mean absolute error.

[0007] However, the characterization of an implant with this optimization method is not satisfactory because it does not allow reliable refractive correction values ​​to be predicted.

[0008] The invention aims in particular to overcome these drawbacks. Subject matter and summary of the invention

[0009] Thus, and according to a first aspect, the invention relates to a method for characterizing a target system comprising a target implant and a target eye, said target system being characterized by an optical performance (CP) and a power (P) of said target implant, said method comprising the following steps: - obtaining an optical property adjustment value, intended to adjust at least one adjustable optical property of said target system, - obtaining an optical performance adjustment value of said target system; - determining a correspondence between said power and the optical performance from at least one optical property of the target system, at least one of which is adjustable, from said optical property adjustment value and from said performance adjustment value, the determination comprising the steps: (i) adjusting a value of said adjustable property with said optical property adjustment value, (ii) adjusting a value of said optical performance or power with said performance adjustment value, said optical property adjustment value having been determined to minimize a dispersion of errors, each of said errors being: (i) a difference between an initially predicted value, from a given value of said power, of said optical performance and a measured value of said optical performance, or (ii) a difference between an initially predicted value, from the measured value of said optical performance, of said power and the given value of said power, for a reference system of a type of said target system and comprising a reference eye and a reference implant; said performance adjustment value having been determined so as to cancel a bias of said errors obtained when said dispersion is minimal.

[0010] Correlatively, the invention also proposes a device for characterizing a target system comprising a target implant and a target eye, said target system being characterized by an optical performance and a power of said target implant, said method comprising: - a module for obtaining an optical property adjustment value, intended to adjust at least one adjustable optical property of said target system, - a module for obtaining an optical performance adjustment value of said target system; - a module for determining a correspondence between said power and the optical performance from at least one optical property of the target system, at least one of which is adjustable, from said optical property adjustment value and from said performance adjustment value, the determination comprising the steps: (i) adjusting a value of said adjustable property with said optical property adjustment value, (ii) adjusting a value of said optical performance or power with said performance adjustment value, said optical property adjustment value having been determined to minimize a dispersion (SDA) of errors, each of said errors being: (i) a difference between an initially predicted value, from a given value of said power (P), of said optical performance and a measured value of said optical performance, or (ii) a difference between an initially predicted value, from the measured value of said optical performance, of said power and the given value of said power, for a reference system of a type of said target system and comprising a reference eye and a reference implant; said performance adjustment value having been determined so as to cancel a bias of said errors obtained when said dispersion is minimal.

[0011] In this document, the term "eye implant system" refers to an assembly comprising at least one eye and one implant, and possibly other optical elements, for example glasses or lenses.

[0012] In this document, and for the sake of simplification, we will call: - “optical property” means the property as such (e.g., the curvature of the cornea) or a value of that property (e.g., a curvature of 45 dioptres); and - “performance” means the performance as such (for example a refractive correction) or a value of this performance (for example a refractive correction of 2 diopters).

[0013] Let us specify that refractive correction refers to a correction of the vision of the eye by the implant, equivalent to the correction which would be carried out by a lens, glasses or another device placed at a given distance from the eye.

[0014] Thus, and in general, the invention proposes, for a given type of eye implant system, to determine, in a first determination phase, two adjustment values ​​from a set of reference eye implant systems of the same type whose optical performances measured after operation are known, and whose implant powers are also known.

[0015] These first and second adjustment values ​​are determined so that: (i) when the predicted optical performances or the predicted implant powers of each of the reference systems are adjusted by this same first adjustment value, or more precisely when the adjustment value is taken into account in the predicted position of each of the reference implants, the dispersion of the errors between the predicted and known optical performances or powers is minimized; (ii) when the predicted optical performances or the predicted implant powers of each of the reference systems are adjusted by this same second adjustment value, the bias of the errors between the predicted and known optical performances or powers is canceled.

[0016] Thus, the two criteria (dispersion and bias) characterizing the reliability of the predictions for the reference systems are jointly minimized by taking into account the two adjustment values ​​in the calculation of the optical performance or the power.

[0017] In a second characterization phase, when it is a question of determining the optical performance of a target system of the same type or the power of a target implant, these two adjustment values ​​are used.

[0018] Cancelling the bias makes it possible to obtain accurate predictions.

[0019] But the fact of, at the same time, minimizing the dispersion and canceling the bias makes it possible to obtain predictions that are not only accurate but also precise (in English "precise"), which is not possible with the state-of-the-art methods.

[0020] The invention proposes to use two adjustment values ​​to achieve this objective.

[0021] In particular, taking into account the first adjustment value minimizing a dispersion makes it possible to reduce the uncertainty on the predictions. Indeed, the dispersion of the prediction errors on a set of reference systems quantifies the difference between the smallest and largest of these errors. If this difference is small (zesi the dispersion is small), we say that the predictions are precise.

[0022] Note here that precise predictions are not necessarily accurate. Conversely, accurate predictions are not necessarily precise. Predictions are described as accurate if the average error (also called bias) on these predictions is close to zero. Those skilled in the art sometimes use the term "biased" to describe predictions with poor accuracy, and "unbiased" to describe accurate predictions.

[0023] The methods of the prior art, although they minimize an error criterion, for example such as the mean square error or the mean bias, do not ensure that the dispersion of the errors is minimal. They only aim to obtain good predictions on average. But these methods can lead to significant prediction errors for certain samples.

[0024] The inventors observed that using, as in the prior art, a single adjustment value to cancel the bias or minimize errors in predicting optical performance or implant power, does not minimize the dispersion of these errors.

[0025] Furthermore, and very advantageously, the fact, in the first phase, of determining initially the first value which minimizes the dispersion, then in a second phase, the second value which cancels the bias is simple to implement, and in any case much simpler than a method which would aim to adjust several parameters simultaneously.

[0026] Determining, before implant placement surgery, the optical performance of the eye-implant system or the implant power of this system requires at least one optical property characterizing this system after surgery. In one embodiment, the effective implant-cornea distance is used. This distance does not correspond to the implant-cornea distance observed immediately after implant placement, since the implant undergoes small movements in the days following surgery, before stabilizing.

[0027] The prediction method according to the invention involves obtaining an adjustable optical property. This may be subject to error, for example if it has been predicted or measured with an imprecise method or device. This is particularly the case for the effective implant-cornea distance.

[0028] This error is considered to dominate the rest of the errors in the predictions. This is generally due to the fact that the error caused by inaccuracies in the measurements of other optical properties, for example those arising from biometric measurements, is negligible compared to the error in the adjustable property. It is therefore advisable to choose an adjustable optical property subject to significant prediction or measurement errors.

[0029] The adjustable optical property can be obtained by any means.

[0030] In any event, only the value of the adjustable optical property should be known. When the adjustable optical property is predicted, its method of obtaining it can remain secret.

[0031] The characterization method uses a second adjustment value, called performance, to cancel the bias of the predictions.

[0032] This performance adjustment value may typically be subtracted from the initially predicted optical performance or power, to remove bias on this initially predicted performance or power prediction.

[0033] The characterization method establishes a correspondence between the power of the target implant and the optical performance of the target eye-implant system. According to the implementation of the invention: - either the power of the target implant is given, and then the characterization process deduces the optical performance of the system; - either the optical performance of the target power system is given, and the characterization process deduces the power of the target implant.

[0034] According to a second aspect, the invention comprises a method for determining adjustment values ​​intended to characterize a target system comprising a target implant and a target eye, said target system being characterized by an optical performance and a power of said target implant, said method comprising the following steps: - obtaining a history comprising, for at least one reference system of a type of said target system, data comprising: (i) a measured value of its optical performance, (ii) at least one of its optical properties including at least one adjustable property; and (iii) a given value of the power of its reference implant; - calculation based on the same adjustment variable for all reference systems: (i) for said at least one reference system, and using said data, of an error being: (ia) a difference between an initially predicted value and said measured value of its optical performance, or (ib) a difference between an initially predicted value and said given value of the power of its implant; (ii) a dispersion of said errors obtained for a set of said reference systems; - determination of an optical property adjustment value intended to adjust at least one adjustable property of said target system and corresponding to the value of said adjustment variable which minimizes said dispersion, and - determining a performance adjustment value, equal to an average of said errors when said adjustment variable is equal to said optical property adjustment value, and intended to adjust said optical performance or said power of the target system.

[0035] Correlatively, the invention also proposes a device for determining adjustment values ​​intended to characterize a target system comprising a target implant and a target eye, said target system being characterized by an optical performance and a power of said target implant, said method comprising: - a module for obtaining a history comprising, for at least one reference system of a type of said target system, data comprising: (i) a measured value of its optical performance, (ii) at least one of its optical properties including at least one adjustable property; and (iii) a given value of the power of its reference implant; - a calculation module based on the same adjustment variable for all reference systems: (i) for said at least one reference system, and using said data, of an error being: (ia) a difference between an initially predicted value and said measured value of its optical performance, or (ib) a difference between an initially predicted value and said given value of the power of its implant; (ii) a dispersion of said errors obtained for a set of said reference systems; - a module for determining an optical property adjustment value intended to adjust at least one adjustable property of said target system and corresponding to the value of said adjustment variable which minimizes said dispersion, and - a module for determining a performance adjustment value, equal to an average of said errors when said adjustment variable is equal to said optical property adjustment value, and intended to adjust said optical performance or said power of the target system.

[0036] Generally speaking, this method makes it possible to determine, from a data history, corresponding for example to a series of pre- and post-operative results of implant placement surgeries, the adjustment values ​​which will be used, thanks to the implementation of a characterization method such as mentioned above, to characterize an eye-implant system.

[0037] By way of example, the invention in these two aspects can be used by a surgeon who, as his operations progress, establishes a history comprising, for each post-operative eye-implant system of this type, optical properties of this system including at least one adjustable optical property, the power of the implant and a measured value of an optical performance of this system, for example a refractive correction.

[0038] This history allows him to obtain the two adjustment variables for eye-implant systems of this type.

[0039] In this example, when the surgeon plans to operate on the eye of a new patient, he considers an implant to be placed in this patient and thus determines a type of eye implant system.

[0040] Still in this example, the surgeon obtains, for example with biometric measurements, the optical properties of the eye-implant system necessary for the characterization of the eye-implant system of the determined type. He uses the two adjustment variables previously obtained to characterize the eye-implant system envisaged. The surgeon thus obtains, for example, an implant power necessary to obtain a certain refractive correction after stabilization of the implant in the eye.

[0041] According to the invention, a “type of eye implant system” designates any set of characteristics specific to an element of the system (type of eye, age of eye, type of implant, optical design or material of the implant, stabilization system of the implant) or specific to an interaction between these elements (type of installation of the implant in the eye).

[0042] Thus, the characterization method uses two adjustment values ​​determined by the determination method for a type of eye-implant system.

[0043] Two implants of the same power but of different types (for example of different materials), can provide in the same eye a different refractive correction (or any other optical performance). It is therefore advantageous to take into account the type of eye-implant system in the determination and characterization methods presented above.

[0044] Furthermore, the determination of a minimum of dispersion can therefore be carried out in different ways.

[0045] According to a particular embodiment of the determination method, said adjustment variable which minimizes said dispersion is determined by a gradient descent algorithm of said dispersion according to said variable, or by an algorithm consisting of calculating said dispersion for a plurality of values ​​of said adjustment variable and choosing the value which minimizes said dispersion.

[0046] The choice of method may be motivated by different precision and / or time constraints.

[0047] According to a particular mode of implementation of the characterization method, the adjustable optical property is a distance between the target implant and one of the elements of the target eye.

[0048] Similarly, according to a particular mode of implementation of the determination method, the adjustable optical property of a reference system corresponds to a distance between the reference implant and one of the elements of the reference eye.

[0049] According to a particular embodiment of the characterization method, at least one of the optical properties of the target system is obtained from biometric measurements of the target eye, for example with a biometer.

[0050] Similarly, according to a particular mode of implementation of the determination method, at least one of the optical properties of a reference system is obtained from biometric measurements of the target eye of this reference system.

[0051] According to one embodiment of the invention, at least one of the adjustable optical properties of a reference system or a target system is predicted or measured.

[0052] According to one embodiment of the characterization method, at least one of the adjustable optical properties is calculated from at least one optical property of the target eye-implant system. This is particularly the case for the effective implant-cornea distance which can be calculated from optical properties of the eye (such as the length of the eye, the curvature of the cornea, the width of the cornea, etc.) and possibly of the implant (such as its thickness, its curvature, etc.).

[0053] Similarly, according to one embodiment of the determination method, at least one of the adjustable optical properties of at least one reference system is calculated from at least one of said optical properties of this reference system, for example of the eye.

[0054] The formulas allowing these calculations can be determined from various methods.

[0055] In a particular embodiment of the characterization method, the calculation of at least one adjustable optical property is determined from a statistical regression or machine learning technique.

[0056] For example, if we have the properties of many eyes and for each of these eyes a measured value of an adjustable property, for example the effective implant-cornea distance measured after placement of the implant, we can construct, with a regression or machine learning method, a formula to obtain predictions of this adjustable property (from the properties of each eye) which are as close as possible to the measured values ​​of this adjustable property.

[0057] Similarly, according to a particular mode of implementation of the determination method, the calculation of at least one of said adjustable properties of at least one reference system is determined from a regression or machine learning technique.

[0058] According to a particular embodiment of the characterization method, the determination of said optical property adjustment value and said performance adjustment value is carried out by a determination method according to one of the embodiments of the determination method described above.

[0059] According to a particular mode of implementation of one of the methods as described above, the optical performance corresponds to one property among: - a refraction, - a refractive correction, - a focusing position of refracted light rays, - a contrast correction.

[0060] The implant can be used to produce a convergence of light rays at a specific location in the eye, for example the retina. This convergence objective can be expressed by a position relative to the cornea or any other element of the eye, a refractive index, or an optical power expressed in diopters.

[0061] The implant may also be intended to improve the contrast of the retinal image for a given spatial frequency or group of spatial frequencies.

[0062] In one embodiment, a single optical property adjustment value and a single performance adjustment value are used.

[0063] This embodiment with a reduced number of adjustable parameters advantageously makes it possible to improve the capacity of the model to make predictions on new data with a quality close to predictions on data used to construct this model.

[0064] The invention also proposes a system comprising at least one computer equipment, for example a biometer, comprising at least one characterization device and / or one determination device as described above.

[0065] Thus, the invention makes it possible to implement several configurations, in particular: - a characterization device alone, - a determination device alone, or - a system grouping the two devices.

[0066] In one embodiment of the invention, the device for determining adjustment values ​​is a computer capable of communicating these values ​​to a biometer comprising a characterization device.

[0067] In another embodiment of the invention, the characterization device is integrated into a biometer. Such a biometer can in particular obtain the optical properties by biometric measurements and use these optical properties to characterize an eye-implant system.

[0068] It is also possible to collect biometric data provided by a third party. Thus, a computer can be used to implement the characterization method and the determination method, without the need for a biometer.

[0069] The invention proposes a computer program comprising instructions for executing the steps of a characterization method according to any one of the implementation modes described above.

[0070] The invention proposes a computer program comprising instructions for executing the steps of a determination method according to any one of the implementation modes described above.

[0071] It should be noted that the computer programs mentioned in this disclosure may use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0072] The invention also proposes a recording medium readable by computer equipment and / or a biometer, of a computer program comprising instructions for executing the steps of a characterization method according to one of the modes described above.

[0073] The invention also provides a recording medium readable by computer equipment and / or a biometer, of a computer program comprising instructions for carrying out the steps of a determination method according to one of the methods described above.

[0074] The recording media mentioned in this disclosure may be any entity or device capable of storing the program and being read by a biometer or by any computer equipment, in particular a computer.

[0075] For example, the medium may comprise a storage means, or even a magnetic recording means, for example a hard disk.

[0076] Alternatively, the recording media may correspond to a circuit integrated into a computer or a biometer, circuit in which the program is incorporated, and adapted to execute a method as described above or to be used in the execution of this method. Brief description of the figures

[0077] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof without any limiting character.

[0078] [Fig.l] [Fig.l] represents a method for determining adjustment values ​​in accordance with a particular embodiment of the invention.

[0079] [Fig.2] [Fig.2] represents a data item from a history that can be used in a particular embodiment of the invention.

[0080] [Fig.3] [Fig.3] represents adjustment values ​​within the meaning of the invention.

[0081] [Fig.4] [Fig.4] represents an example of a dispersion, a bias and an error absolute mean as a function of an adjustment variable of an adjustable property in accordance with a particular mode of implementation of the invention.

[0082] [Fig.5] [Fig.5] represents a device for determining adjustment values ​​in accordance with a particular embodiment of the invention.

[0083] [Fig. 6] [Fig. 6] represents two modes of implementation of a method for characterizing a target system in accordance with a particular mode of implementation of the invention.

[0084] [Fig.7] [Fig.7] represents a device for characterizing a target system in accordance with a particular mode of implementation of the invention.

[0085] [Fig.8] [Fig.8] represents a first system according to a particular mode of implementation of the invention.

[0086] [Fig.9] [Fig.9] represents a second system according to a particular mode of implementation of the invention.

[0087] [Fig. 10] [Fig. 10] represents a third system according to a particular mode of implementation of the invention.

[0088] [Fig. 11] [Fig. 11] represents a fourth system according to a particular mode of implementation of the invention.

[0089] [Fig. 12] [Fig. 12] represents the hardware architecture of a determination device according to a particular mode of implementation of the invention.

[0090] [Fig. 13] [Fig. 13] represents the hardware architecture of a characterization device according to a particular mode of implementation of the invention.

[0091] Description of particular embodiments of the invention

[0092] We will now describe several embodiments of the invention. Generally speaking, and as mentioned previously, the invention provides a method for determining adjustment values ​​that can be used to characterize a target system, and a method for characterizing a target system using such adjustment values.

[0093] With reference to Figures 1 and 2, the determination of the adjustment values ​​will be described and with reference to Figures 3 and 4 the characterization of a target system with such adjustment values.

[0094] [Fig.l] represents the main steps of a method for determining adjustment values ​​intended to characterize a target system in accordance with a particular embodiment of the invention.

[0095] These adjustment values ​​are determined based on a history of data relating to reference eye-implant systems of the type of the target system. Each reference system comprises a reference eye and a reference implant.

[0096] Thus, in the mode described here, this determination method comprises a step E100 of obtaining a history of HrHN data.

[0097] [Fig.2] represents a data item Hn in a particular embodiment of the invention.

[0098] In the embodiment described here, this data Hn comprises one or more optical properties POn of a reference system SRn of the type of the target system, including at least one adjustable optical property PAn, the power Pn of the implant In of this reference system SRn comprising this implant In and a reference eye On, and a value CMn of an optical performance CP measured after the installation and stabilization of the implant.

[0099] In a particular embodiment, the adjustable property PAn of a reference system SRn is the implant-cornea distance of this system which can take into account an angle between an axis of the reference eye and an axis of the reference implant.

[0100] The determination method comprises a step E1 10 of calculating, as a function of an adjustment variable A, for all the data Hn of the history, a predicted value CPnA of the optical performance of the corresponding reference system SRn,

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[0112] and an EnA prediction error by taking the difference between this CPnA value and the measured optical performance CMn. In an embodiment in which the optical performance CP is a refractive correction, the determination method uses the following formula EQ1: Ei=CPÎ-CM„ = =r=r-CM„ (EQD . LLLLLLL TO LLLLLLLV 'a'' P xZÆûïi ' where ALn is the length of the reference eye (On), nvn the refractive index of the ocular medium behind the implant (the vitreous), nan the refractive index of the ocular medium in front of the implant (the aqueous humor), VKn the power of the cornea of ​​the reference eye, and dn the distance between the fictitious spectacle lens and the cornea of ​​the reference eye. Note that in the case where the calculated error EnA would be a difference between the power PnA calculated from the measured refractive correction CMn and the given power Pn of the reference implant In, the following formula could be used instead of the formula EQ1 to calculate this error EnA: pA _pA _p _ ~ * n * h~ .......................................na»............_ » (EQ2) AL^ (P^A) -(PA^A) n In the calculation where the adjustable optical property PAn is an implant-cornea distance, this can in particular be calculated by the formula EQ10 described below. In the embodiment described here, the determination method comprises a step E1 15 of calculating a dispersion SDA of the errors EnA as a function of the adjustment variable A: N where Ba is the bias, that is, the average over n of the EnA errors. In the embodiment described here, the determination method comprises a step E120 of determining, from the formulas EQ1 and EQ2, the value of the variable A which minimizes the dispersion SDA. An algorithm to minimize this dispersion may consist of calculating a plurality of values ​​of A and choosing the value that corresponds to the smallest dispersion value SDa. Another example of an algorithm for determining the minimum of the SDA dispersion is a gradient descent algorithm. This would involve, for example, performing successive iterations, in each of which the derivative of the dispersion is calculated dSPA then we subtract from the value of A a term proportional to this derivative, then we dA chooses for the next iteration the value of the dispersion taken at this new value of A. This process can for example stop when the derivative of the dispersion has become very small.

[0113] We thus obtain the adjustment value (Cl) of optical property which minimizes the SDA dispersion of the EnA errors:

[0114] c 1 = ar gminSD4 (EQ4) A

[0115] During a step E130, the determination method obtains the performance adjustment value C2, equal to the bias obtained at the minimum dispersion (or residual error), that is to say: [0H6] £A^(EQ5)

[0117] A particular embodiment of obtaining these adjustment values ​​C1 and C2 is illustrated in [Fig.3]: C1 corresponds to the value of A which minimizes the SDA dispersion and C2 is the residual error obtained at this value of A. In this figure is also represented an adjustment value C0 which would correspond to the value of A which cancels the BA bias. It appears in this figure that this value C0 is far from the minimum dispersion C1.

[0118] [Fig.4] represents results obtained on a data history corresponding to a set of eyes operated with Tecnis PCB00 implants and for which the calculation of the effective implant-cornea distance is carried out with the formula called "HofferQ formula" (many other formulas exist, for example the Olsen, Haigis, Holladay II formulas, the SRK T formula etc.). These results are the dispersion SDA of the errors, the bias BA and the mean absolute error AEa, all as a function of the adjustment variable A of the effective implant-cornea distance. In this example, the errors are differences between predicted values ​​and measured values ​​of the refractive correction of the implant.

[0119] We can see on the one hand that the minima of dispersion and of the mean absolute error are quite distinct. On the other hand, the minimum of the mean absolute error is very close to the zero of the bias.

[0120] [Fig.5] represents a determination device D99 in accordance with a particular embodiment of the invention for determining adjustment values ​​C1 and C2.

[0121] This device D99 includes a module D100 for obtaining a history of HrHN data.

[0122] This device D99 comprises a module DI 10 configured to obtain these data Hn and to calculate errors EnA from these data and as a function of an adjustment variable A.

[0123] This device D99 includes a DI 15 module for calculating the SDA dispersion of these EnA errors.

[0124] The device D99 comprises a module D120 configured to use the dispersion SDa provided by the module DI 15 and determine the value Cl of the variable A which minimizes this dispersion SDA.

[0125] The device D99 comprises a module 130 configured to use the value Cl provided by the module D120 and to obtain the average C2 of the errors EnA when the variable A is equal to the value CL

[0126] The implementation of the determination method makes it possible to obtain, for at least one type of eye implant system, an optical property adjustment value C1 and a performance adjustment value C2. These adjustment values ​​can be used to characterize a target eye implant system of this type.

[0127] [Fig. 6] represents two embodiments of a characterization method in accordance with the invention (Figures 6A and 6B).

[0128] Figure 6A represents a first embodiment of a method for characterizing a target system of a T type comprising a target implant and a target eye.

[0129] The method of FIG. 6A comprises a step E5 of obtaining the type T of the target system, an optical performance CP of the target system, one or more optical properties PO of this target system including an adjustable optical property PA.

[0130] This method aims to obtain the power P of the target implant which will make it possible to obtain this optical performance CP once the implant is placed in the target eye and stabilized.

[0131] In this embodiment, the optical performance CP is a refractive correction by the cornea of ​​the target eye and the implant of the target system, which would be equivalent to the refractive correction provided by a fictitious spectacle lens placed at a fixed distance d from this eye.

[0132] In this embodiment, the adjustable optical property PA is an implant-cornea distance.

[0133] During a step E10, an optical property adjustment value Cl for T-type eye-implant systems is obtained.

[0134] During a step E20, an optical performance adjustment value C2 for T-type eye-implant systems is obtained.

[0135] The optical property adjustment value Cl is a value that has been determined to minimize a dispersion of errors, each of the errors being a difference between

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[0144]

[0145]

[0146] an initially predicted value of the optical performance and a measured value of this optical performance for a reference system of the type T of the target system. The adjustment value of a C2 performance is a value that has been determined so as to cancel out a bias of these errors when the dispersion is minimal. The characterization process can obtain these Cl and C2 adjustment values ​​by any means. For example, they are recorded in a table in association with a type of eye-implant system. In one example, these adjustment values ​​C1 and C2 are determined by implementing a determination method in accordance with the invention and an example of which has been described with reference to [Fig.l]. In the embodiment described here, during a step E30, the method of FIG. 6A determines the power P from the optical performance CP, in three sub-steps. A first sub-step E30A comprises adjusting the value of the adjustable property PA by adding the optical performance CP and the optical property adjustment value Cl. A second sub-step E30B comprises adjusting the value of the optical performance CP by subtracting the performance adjustment value C2 from the optical performance CP obtained in step E5. A third sub-step E300 calculates the power P of the target implant from the optical property(ies) PO, the adjusted value of the optical performance CP and the adjusted value of the adjustable optical property PA. In the case where the optical performance CP is a refractive correction and the adjustable optical property PA is an implant-cornea distance, this calculation can be based on a physical model of the eye that establishes a formula expressing the power P of the implant as a function of the refractive correction CP. An example of such a formula is: ----_------2«-----, (EQ6) AL-(PA+CÙ „ / -r^--PA+Cl -=-+1- 6- where the eye length AL, the refractive index nv of the ocular medium behind the implant (the vitreous), the refractive index na of the ocular medium in front of the implant (the aqueous humor), the power VK of the cornea, the distance d between a fictitious spectacle lens and the cornea, and the implant-cornea distance PA are optical properties PO of the target system. Note that in this example, equation EQ6 takes into account the adjusted values ​​of the implant-cornea distance (PA+C1) and the refractive correction (CP-C2).

[0147] If the adjustment value C2 were, according to another embodiment, intended to adjust the power P of the target implant, the formula EQ5 would be replaced by the formula:

[0148] p = ---_ C? (EQ7) AL-(PA+C1) ^—-(PA+C1)

[0149] Figure 6B represents a second embodiment of a method for characterizing a T-type target system comprising a target implant and a target eye.

[0150] The steps of Figure 6B that have the same reference as those of Figure 6A are identical or similar to those of Figure 6A.

[0151] The method of figure 6B comprises a step E5' of obtaining the type T of the target system, a power P of the target implant of the target system, one or more optical properties PO of this target system including an adjustable optical property PA.

[0152] This method aims to obtain the optical performance CP of the target system which would be obtained once the target implant of power P is placed in the target eye and stabilized.

[0153] Step E5' is followed by steps E10 and E20 already described to obtain the two adjustment values ​​C1 and C2.

[0154] In the embodiment described here, step E20 is followed by a step E30', which determines the optical performance CP from the power P, in three sub-steps E30A, E300' and E30B.

[0155] The first step E30A, identical or similar to that described with reference to FIG. 6A, adjusts the adjustable property PA obtained in step E5'.

[0156] In the embodiment described here, the second step E300' calculates the optical performance CP from the power P, the optical property(ies) PO and the adjusted value of the adjustable optical property PA.

[0157] The third step E30B, identical or similar to that described with reference to FIG. 6A, adjusts the optical performance CP obtained in step E300'.

[0158] In the calculation where the optical performance CP is a refractive correction and where the adjustable optical property PA is an implant-cornea distance, we can use the inverse formula of that given previously written (EQ6), to express the correction CP as a function of the power P, and taking into account the two adjustment values ​​C1,C2:

[0159] CP =---r----C?(EQ8)

[0160] If the adjustment value C2 were, according to another embodiment, intended to adjust the power P of the target implant, the formula EQ6 would be replaced by the formula:

[0161] CP = -----1-----(EQ9) ,,-,.,-1..........y JFK

[0162] In the embodiment of Figures 6A and 6B, the adjustable optical property PA was given as input to the method (steps E0 or E0'). In another embodiment, the adjustable optical property PA, for example the effective implant-cornea distance, is deduced from the other optical properties PO.

[0163] In the calculation where the adjustable optical property PA is an implant-cornea distance, this can be calculated by a wide variety of formulas, generally deduced from statistical learning. Such a formula can for example result from a linear regression, an example of which is:

[0164] PA - üq + alx K +0^ AL + a3x WTW (EQ10)

[0165] where a0-a3 are regression coefficients, K, AL and WTW are properties of the eye considered (K: curvature of the cornea, AL: length of the eye, WTW: width of the cornea) and which constitute an example of optical properties (OP). Let us emphasize that such a formula can be made more complex by taking other optical properties and additional coefficients as input, and / or by using non-linear functions. Let us also recall that this formula can be secret.

[0166] [Fig.7] represents a device D0 for characterizing a target system in accordance with a particular embodiment of the invention.

[0167] This device D0 includes a module D5 for obtaining: - of a type T of the target system, - an optical performance CP of this target system or a power P of the target implant of this target system, - one or more optical properties PO of this target system including an adjustable optical property PA.

[0168] This device D0 further comprises: - a D10 module for obtaining an optical property Cl adjustment value, - a D20 module for obtaining an optical performance adjustment value C2, - a D30 module for determining a correspondence between a power of the target implant and an optical performance of the target system, itself comprising three sub-modules: (i) a D30A adjustment sub-module for an adjustable optical property, (ii) a D30B adjustment sub-module for an optical performance; and (iii) a D300 sub-module for calculating a correspondence between the optical performance CP and the power P.

[0169] Depending on its configuration, this DO device is configured to implement the method for characterizing the target system described previously with reference to FIG. 6A or 6B.

[0170] [Fig.8] represents an embodiment in which the prediction and determination methods as described above are implemented in a D200A system comprising a BIO biometer and an E1 computer.

[0171] The biometer BIO comprises a device DO which implements the method of characterizing a target system by determining a power P of the target implant and an optical performance CP of the target system, for example its refractive correction.

[0172] For each target eye, the BIO biometer performs biometric measurements from which optical properties PO of this eye are derived. The biometer also provides an adjustable optical property PA, for example the implant-cornea distance predicted from the optical properties PO, for example using the HofferQ formula.

[0173] According to the prediction method described above and implemented on the device D10, the optical performance CP, for example the refractive correction, is obtained from one or more optical properties PO including an adjustable optical property PA, for example the implant-cornea distance PA and adjustment values ​​Cl and C2 adapted to the type T of the target implant and provided by the computer El.

[0174] This computer El comprises a device D99 implementing a method for determining the adjustment values ​​Cl and C2 as described above. The history H comprising the data Hn of reference eye-implant systems SRn making it possible to determine the adjustment values ​​Cl and C2, is recorded on a hard disk of the computer EL.

[0175] In a particular embodiment, this history is constructed with the BIO biometer of the same system. In this case, the BIO biometer can, in addition to performing biometric measurements on reference eyes, perform refractive correction measurements of the reference eye-implant systems after the implant has been placed and stabilized.

[0176] This scenario may, for example, correspond to the use, by a surgeon, of the D200A system on the one hand to characterize target eye-implant systems and thus prepare surgical implant placement operations, and on the other hand to collect pre- and post-operative data to determine new adjustment values, with the aim of improving future characterizations of eye-implant systems, and therefore improving future implant placement operations.

[0177] [Fig.9] represents an embodiment in which the method for characterizing a target implant described above is implemented by a D200B system comprising a BIO biometer. The BIO biometer comprises the device D0 which implements this characterization method. The implementation of this method differs then of its mode of implementation represented in [Fig.8] in that the adjustment values ​​Cl and C2 are provided by a third party to the D200B system.

[0178] [Fig. 10] represents an embodiment in which the method for determining adjustment values ​​C1 and C2 as described above is implemented in a system D200C comprising a computer E1. The computer E1 comprises the device D99 which implements the method for determining adjustment values. The implementation of this determination method then differs from its mode of implementation represented in [Fig.8] in that the history H is provided by a third party to the system D200C.

[0179] [Fig. 11] represents an embodiment in which the prediction and determination methods as described above are implemented in a D200D system comprising a computer comprising both a characterization device DO of a target system and the determination device D99. The difference with the embodiment represented in [Fig. 8] is that the biometric measurements cannot then be carried out by this system and the optical properties PO are then provided to it by a third party to the D200D system.

[0180] [Fig. 12] represents the hardware architecture of a D99 determination device according to a particular embodiment of the invention.

[0181] In the embodiment described here, the determination device D99 has a hardware architecture of a computer. It notably comprises a processor D991, a read-only memory D992, a random access memory D993, a rewritable non-volatile memory D994 and communication means D995.

[0182] The read-only memory D992 of the device D99 constitutes a recording medium in accordance with the invention, readable by the processor D991 and on which is recorded a computer program PGD in accordance with the invention, this program comprising instructions for executing the steps of a determination method according to the invention described previously with reference to [Fig.l] in one embodiment.

[0183] The computer program PGD defines functional modules of the determination device D99 represented in [Fig.5].

[0184] [Fig. 13] represents the hardware architecture of a characterization device D0 in accordance with a particular embodiment of the invention.

[0185] In the embodiment described here, the characterization device D0 has a hardware architecture of a computer. It notably comprises a processor D01, a read-only memory D02, a random access memory D03, a rewritable non-volatile memory D04 and communication means D05.

[0186] The read-only memory D02 of the device D0 constitutes a recording medium in accordance with the invention, readable by the processor D01 and on which is recorded a computer program PGC in accordance with the invention, this program comprising instructions for carrying out the steps of a characterization method according to the invention described previously with reference to Figures 6A and 6B in two embodiments.

[0187] The PGC computer program defines functional modules of the DO characterization device represented in [Fig.7].

Claims

1. Claims Method for acquiring biometric measurements and characterizing a target system comprising a target implant and said target eye, this method comprising: a computer-implemented method for characterizing said target system, said target system being characterized by an optical performance (CP) and a power (P) of said target implant, said characterization method comprising the following steps: - obtaining (E10) an optical property adjustment value (Cl), intended to adjust at least one adjustable optical property (PA) of said target system (SC), - obtaining (E20) an optical performance adjustment value (C2) of said target system; - determination (E30, E30') of a correspondence between said power (P) and the optical performance (CP) from at least one optical property (PO) of the target system including at least one adjustable property (PA), from said optical property adjustment value (Cl) and from said performance adjustment value (C2); said determination (E30, E30') of a correspondence between said power (P) and the optical performance (CP) being: - a determination (E30') of said optical performance (CP) as a function of said power (P); or - a determination (E30) of said power (P) as a function of said optical performance (CP), the determination (E30,E30') comprising the steps: (i) adjusting (E30A) a value of said adjustable property (PA) with said optical property adjustment value (Cl), (ii) adjusting (E30B) a value of said optical performance (CP) or said power (P) with said performance adjustment value (C2), said optical property adjustment value (Cl) having been determined to minimize a dispersion (SDA) of errors (EnA), each of said errors (EnA) being: (i) a difference between an initially predicted value, from a given value of said power (P), of said optical performance (CP) and a measured value of said optical performance, or (ii) a difference between an initially predicted value, from the measured value of said optical performance, of said power (P) and the given value of said power (P), for a reference system (SRn) of a type (T) of said target system and comprising a reference eye (On) and a reference implant (In); said performance adjustment value (C2) having been determined so as to cancel a bias of said errors (EnA) obtained when said dispersion (SDA) is minimal, at least one of said optical properties (PO) being obtained from said biometric measurements of the target eye; and said method for acquiring biometric measurements and characterizing a target system being further characterized in that it comprises an acquisition of said biometric measurements of said target eye by a biometer.

2. Acquisition and characterization method according to claim 1 wherein said at least one adjustable optical property (PA) is a distance between the target implant and one of the elements of the target eye.

3. Acquisition and characterization method according to one of claims 1 to 2 in which at least one of said adjustable properties (PA) is calculated from at least one of said optical properties (PO).

4. Acquisition and characterization method according to claim 3 according to which the calculation of at least one of said adjustable properties (PA) is determined from a statistical regression or machine learning technique.

5. Method for acquiring biometric measurements and determining adjustment values ​​intended to characterize a target system comprising a target implant and a target eye, said method comprising: A / a computer-implemented method for determining adjustment values ​​(Cl, C2) intended to characterize said target system, said target system being characterized by an optical performance (CP) and a power (P) of said target implant, said method for determining values ​​comprising the following steps:

6. - obtaining (E100) a history comprising, for at least one reference system (SRn) of a type (T) of said target system, data (Hn) comprising: (i) a measured value (CMn) of its optical performance (CP), (ii) at least one of its optical properties (POn) including at least one adjustable property (PAn), at least one said optical property of an eye of a said reference system being obtained from biometric measurements; and (iii) a given value (Pn) of the power (P) of its reference implant (In); - calculation (El 10,El 15) as a function of the same adjustment variable (A) for all reference systems (SRn): (i) for said at least one reference system (SRn), and using said data (Hn), of an error (EnA) being: (ia) a difference between an initially predicted value (CPnA) and said measured value (CMn) of its optical performance (CP), or (ib) a difference between an initially predicted value (PnA) and said given value (Pn) of the power of its implant (In); (ii) a dispersion (SDA) of said errors (EnA) obtained for a set of said reference systems (SRn); - determination (E120) of an optical property adjustment value (Cl) intended to adjust at least one adjustable property (PA) of said target system and corresponding to the value of said adjustment variable (A) which minimizes said dispersion (SDA), and - determination (E130) of a performance adjustment value (C2), equal to an average of said errors (EnA) when said adjustment variable (A) is equal to said optical property adjustment value (Cl), and intended to adjust said optical performance (CP) or said power (P) of the target system, said method for acquiring biometric measurements and determining adjustment values ​​being further characterized in that it comprises an acquisition of said biometric measurements of the eye of said at least one reference system by a biometer. Acquisition and determination method according to claim 5 wherein the value of said adjustment variable (A) which minimizes said dispersion (SDA) is determined (El20) by a gradient descent algorithm of said dispersion (SDA) according to said variable (A), or by an algorithm consisting of calculating said dispersion (SDA) for a plurality of values ​​of said adjustment variable (A) and choosing the value which minimizes said dispersion (SDA).

7. Acquisition and determination method according to claim 5 or 6 wherein said at least one adjustable optical property (PA n) of each reference system (SRn) corresponds to a distance between the reference implant (In) and one of the elements of the reference eye (On).

8. Acquisition and determination method according to one of claims 5 to 7 in which at least one optical properties (POn) of at least one reference system (SRn) are obtained from biometric measurements of the eye of this reference system (SRn).

9. Acquisition and determination method according to one of claims 5 to 8 in which at least one of the adjustable properties (PAn) of at least one reference system (SRn) is calculated from at least one of said optical properties (POn) of this reference system (SRn).

10. Acquisition and determination method according to claim 9 according to which the calculation of at least one of said adjustable properties (PAn) of at least one reference system (SRn) is determined from a regression or machine learning technique.

11. Characterization acquisition method according to one of claims 1 to 4 wherein the determination of said optical property adjustment value (Cl) and said performance adjustment value (C2) is carried out by an acquisition and determination method according to one of claims 5 to 1 H

12. 1U. Method according to one of claims 1 to 11 in which said optical performance (CP) corresponds to one property among: - a refraction, - a refractive correction, - a focusing position of refracted light rays, - a contrast correction.

13. Method according to one of claims 1 to 12 in which two said eye-implant systems are of the same type if they have in common at least: - a characteristic of the implants of said systems; - a characteristic of the eyes of said systems; - a characteristic of the interactions between the eye and the implant of said systems.

14. Method according to one of claims 1 to 13 in which a single optical property adjustment value (Cl) and a single performance adjustment value (C2) are used.

15. System comprising a biometer and a device (DO) for characterizing a target system comprising a target implant and a target eye, said target system being characterized by an optical performance (CP) and a power (P) of said target implant, said device comprising: - a module for obtaining (D10) an optical property adjustment value (Cl), intended to adjust at least one adjustable optical property (PA) of said target system (SC), - a module for obtaining (D20) an optical performance adjustment value (C2) of said target system; - a module for determining (D30) a correspondence between said power (P) and the optical performance (CP) from at least one optical property (PO) of the target system, at least one of which is adjustable (PA), said optical property adjustment value (Cl) and said performance adjustment value (C2);said determination (E30, E30') of a correspondence between said power (P) and the optical performance (CP) being: - a determination of said optical performance (CP) as a function of said power (P); or - a determination of said power (P) as a function of said optical performance (CP), the determination (E30, E30') comprising the steps of: (i) adjusting (E30A) a value of said adjustable property (PA) with said optical property adjustment value (Cl), (ii) adjusting (E30B) a value of said optical performance (CP) or of said power (P) with said performance adjustment value (C2),; said optical property adjustment value (Cl) having been determined to minimize a dispersion (SDA) of errors (EnA), each of said errors (EnA) being: (i) a difference between an initially predicted value, from a given value of said power (P), of said optical performance (CP) and a measured value of said optical performance, or (ii) a difference between an initially predicted value, from the measured value of said optical performance, of said power (P) and the given value of said power (P), for a reference system (SRn) of a type (T) of said target system and comprising a reference eye (On) and a reference implant (In);said performance adjustment value (C2) having been determined so as to cancel a bias of said errors (EnA) obtained when said dispersion (SDA) is minimal, at least one of said optical properties (PO) being obtained from biometric measurements of the target eye acquired by said biometer.;

16. System comprising a biometer and a device (D99) for determining adjustment values ​​(Cl, C2) intended to characterize a target system comprising a target implant and a target eye, said target system being characterized by an optical performance (CP) and a power (P) of said target implant, said device comprising: - a module for obtaining (D100) a history comprising, for at least one reference system (SRn) of a type (T) of said target system, a data item (Hn) comprising: (i) a measured value (CMn) of its optical performance (CP), (ii) at least one of its optical properties (POn) including at least one adjustable property (PAn), at least one said optical property of an eye of a said reference system being obtained from biometric measurements acquired by said biometer; and (iii) a given value (Pn) of the power (P) of its reference implant (In);- a calculation module (DI 10, DI 15) as a function of the same adjustment variable (A) for all the reference systems (SRn): (i) for said at least one reference system (SRn), and using its said data (Hn), of an error (EnA) being:; (ia) a difference between an initially predicted value (CPnA) and said measured value (CMn) of its optical performance (CP), or (ib) a difference between an initially predicted value (PnA) and said given value (Pn) of the power of its implant (In); (ii) a dispersion (SDA) of said errors (EnA) obtained for a set of said reference systems (SRn); - a determination module (D120), of an optical property adjustment value (Cl) intended to adjust at least one adjustable property (PA) of said target system and corresponding to the value of said adjustment variable (A) which minimizes said dispersion (SDA), and - a determination module (DI30) of a performance adjustment value (C2), equal to an average of said errors (EnA) when said adjustment variable (A) is equal to said optical property adjustment value (Cl), and intended to adjust said optical performance (CP) or said power (P) of the target system.

17. Computer program (PGD, PGC) comprising instructions which, when the program is executed by computer equipment, cause the latter to implement: - steps of a determination method according to at least one of claims 1 to 5 and / or - steps of a characterization method according to at least one of claims 6 to 11.

18. Recording medium (D992, D02) readable by computer equipment and / or a biometer, of a computer program (PGD, PGC) comprising instructions for executing the steps of a determination method according to at least one of claims 1 to 5 and / or the steps of a characterization method according to at least one of claims 6 to 11.

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