WO2021222047A1

WO2021222047A1 - Fitting system for implantable lenses

Info

Publication number: WO2021222047A1
Application number: PCT/US2021/029030
Authority: WO
Inventors: Dan Reinstein; Timothy James ARCHER; Ryan VIDA
Original assignee: Dan Reinstein
Priority date: 2020-04-26
Filing date: 2021-04-25
Publication date: 2021-11-04
Also published as: CN115460971A; KR20230002375A

Abstract

The present disclosure includes an imaging system and a method for operating an imaging system. The method includes generating an estimate of the position of a PIOL that corrects a vision deficit in a patient's eye from anatomical parameters describing the patient's eye, the PIOL having a particular, and generating a three-dimensional graphical representation of a distance between a back surface of the PIOL and a crystalline lens of the patient's eye and displaying the three-dimensional graphical representation on a display controlled by the imaging system.

Description

Fitting System for Implantable Lenses

Background

[0001] A phakic intraocular lens (PIOL), such as the implantable collamer lens, is an attractive alternative for some patients seeking decreased dependence on glasses and/or contact lenses. The PIOL is inserted surgically between the patient’s crystalline lens and the iris. The height of the back of the PIOL from the plane on which the footplates rest is called the “lens vault” and the separation between back of the PIOL and the anterior surface of the patient’s crystalline lens is known as the “lens separation” but is commonly referred to in ophthalmology as the PIOL “vault”. Selecting the correct size for the PIOL presents significant challenges. Problems may arise if the size of the PIOL implanted is too large (resulting in very high vault) or too small (resulting in very low or no vault).

[0002] If the size of the implanted PIOL is too large and the resulting vault is too high then the PIOL may push the iris forward. This can lead to narrowing of the anterior chamber angle which may increase the risk for intraocular pressure changes with subsequent irreversible glaucomatous nerve damage. In addition, the back surface of the iris, the pigment epithelium of the iris, can be excessively rubbed/chaffed against by the oversized PIOL causing the pigment of the iris to rub off and disperse into the anterior chamber. Unwanted pigment cells in the anterior chamber may affect the trabecular meshwork causing increased fluid outflow resistance, an increase in intraocular pressure and glaucomatous nerve damage.

[0003] If the size of the implanted PIOL is too small and the resulting vault is too low, then the PIOL may come into contact with the anterior surface of the crystalline lens. This may result in early cataract formation. In addition, if the vault of the PIOL is too low (even if not touching the anterior surface of the crystalline lens), then it may interfere with the flow of nutrients to the crystalline lens which also may contribute to early cataract formation. Finally, the size of the crystalline lens can increase over time, and hence, there must be sufficient space between the PIOL and crystalline lens surface to provide room for the crystalline lens to grow. [0004] It would be advantageous to provide a surgeon with a detailed map of the spacing between the PIOL and the crystalline lens for each of the possible PIOL sizes that are available for the desired vision correction for the particular patient considering surgery.

Summary

[0005] The present disclosure includes a method for operating an imaging system and an imaging system. The method includes generating an estimate of the position of a PIOL that corrects a vision deficit in a patient's eye from anatomical parameters describing the patient's eye, the PIOL having a particular, and generating a three-dimensional graphical representation of a distance between a back surface of the PIOL and a crystalline lens of the patient's eye and displaying the three-dimensional graphical representation on a display controlled by the imaging system.

[0006] In one aspect, the anatomical parameters are measured by the imaging system.

[0007] In another aspect, the imaging system is an ultrasound imaging system adapted for scanning a patient's eye.

[0008] In another aspect, the method is repeated for different size PIOLs.

[0009] In another aspect, the method includes generating a cross-sectional view of the patient's eye showing the estimated position of the PIOL and a surface of the patient's crystalline lens.

[0010] In another aspect, the method includes generating a cross-sectional view of the patient’s eye showing the estimated position of the PIOL and the shift in position of the iris and the reduction in the angle of the anterior chamber.

[0011] An imaging system according to the present disclosure includes a measurement assembly, a display, and a controller, the controller being adapted to measure anatomical parameters describing a patient's eye using the measurement assembly, to generate an estimate of a position of a PIOL having a particular size that corrects a vision deficit in a patient's eye from the anatomical parameters, and to generate a three-dimensional graphical representation of a distance between a back surface of the PIOL and a crystalline lens of the patient's eye, and displaying the three-dimensional graphical representation on the display.

[0012] In one aspect, measurement assembly comprises an ultrasound imaging system adapted for scanning a patient's eye.

[0013] In another aspect, the controller generates the three-dimensional graphical representation for a plurality of different PIOL sizes.

[0014] In another aspect, the said controller generates a cross-sectional view of said patient's eye showing said estimated position of said PIOL and a surface of said patient's crystalline lens.

[0015] In another aspect, said cross-sectional view further comprises an estimated position of the iris of said patient's eye after said PIOL has been implanted.

Brief Description of the Drawings

[0016] Figure 1 is a cross-sectional view of a portion of an eye illustrating the structures that are relevant to a PIOL implant.

[0017] Figure 2 illustrates the region of the eye shown in Figure 1 after the insertion of a PIOL 21.

[0018] Figure 3 is a top view of a PIOL 21.

[0019] Figure 4 illustrates an exemplary three-dimensional display that provides details of the projected fit to the patient's eye for a PIOL.

[0020] Figure 5 illustrates one embodiment of an imaging system according to the present disclosure. [0021] Figure 6 illustrates a top view of a PIOL 31 that has been implanted in an eye

32.

[0022] Figure 7 illustrates the parameters that are measured with the ultrasound or other scanner.

[0023] Figures 8A-8E, illustrate the manner in which the vault changes with increasing compression of the PIOL in the posterior chamber as a result of the posterior chamber dimensions.

Detailed Description

[0024] The manner in which the present invention provides its advantages can be more easily understood with reference to Figure 1, which is a cross-sectional view of a portion of an eye illustrating the structures that are relevant to a PIOL implant. The cornea is shown at 11. The upper surface of the capsule containing the crystalline lens is shown at 13. The iris 12 is shown at 12. The angle between the iris and the inner surface of the cornea is shown at 16. The ciliary body is shown at 14. The sulcus is shown at 15.

[0025] Refer now to Figure 2, which illustrates the region of the eye shown in Figure 1 after the insertion of a PIOL 21. The PIOL is inserted between the crystalline lens and the iris 12. The feet of the PIOL rest on the region of the zonules, ciliary body, or sulcus, but preferably at or near the lower part of the sulcus. PIOL 21 vaults over crystalline lens capsule 13 as shown at 20. As a result, the length of the surface of the iris rotates about its root upward towards the cornea. This results in the angle at the root 16 decreasing as shown at 16'. The greater the vault 20, the smaller the angle 16 becomes. In addition, the posterior surface of the iris 12 in contact with the PIOL 21 can rub in a manner which results in pigment being released from the iris. The higher the vault, the greater the abrasive forces that can lead to such a release.

[0026] Refer now to Figure 3, which is a top view of a PIOL 21. PIOL 21 includes the central region 22 in which the lens is located and a support region, the haptic or “leg” 24 on each side of region 22. The support regions terminate in two or more footplate feet shown at 23. Feet 23 press against the zonules, ciliary body or sulcus 15 and stabilize the PIOL 21 in place. The material from which PIOL 21 is constructed is flexible. In general, the length of PIOL 21 is greater than the distance between the ciliary body and sulcus points at which PIOL 21 rests, and hence, PIOL 21 is essentially spring-loaded into place. The lens prescription is proportional to the thickness profile and hence the stiffness and mechanical properties of the lens. The amount of force applied to the feet depends on the specific lens prescription, vault 20, and the material from which the insert is made. If the force pushing the feet into the sulcus is insufficient, the PIOL can move after being implanted due to physical forces being applied to the eye of the patient. If the lens moves it may position itself off-center or rotate within the posterior chamber causing optical distortions due to higher order aberrations induced in the visual pathway, for example tilt, coma and astigmatism.

[0027] Preoperative patient examination in preparation for an implant is preferably practiced using a high-frequency ultrasound scanner. Ultrasound scanners are preferred over optical methods because the scanners can observe the physical attributes of the patient’s eye that are covered by the opaque iris, and hence, cannot be directly viewed by optical means. Optical means such as optical coherence tomography scanners can generally image the portions of the posterior chamber within the area exposed by the opening of the pupil. If the pupil is dilated, a greater portion of the posterior chamber can be imaged by such optical means, including the front and back surfaces of the crystalline lens within the aperture of the dilated pupil. The front surface and back surface curvatures may be extrapolated mathematically to estimate posterior chamber dimensions, but direct visualization and measurement of the posterior chamber behind the iris can best be adequately achieved by ultrasound. Lower wavelength optical coherence tomography may penetrate behind the iris and allow imaging behind the iris. Lower wavelength optical coherence tomography causes higher thermal effects during scanning of biological tissues and can be limited in penetrating the iris. It may however, be possible to image the posterior chamber anatomy and geometry by optical means.

[0028] In one aspect of the present invention, the physician scans the patient's eyes with an ultrasound or other imaging system, and a software package on the imaging system generates a three-dimensional map of the predicted distance between the PIOL and the top surface of the patient's lens capsule as a function of position for each of a plurality of different sized PIOLs that are available for the patient. [0029] Refer now to Figure 4, which illustrates an exemplary three-dimensional display that provides details of the projected fit to the patient's eye for a PIOL. The display includes the projected placement of the PIOL 72 within the patient's eye 71. Exemplary distances between the PIOL and the capsule are provided as shown at 73. In addition, the region inside the PIOL is coded to indicate the distance between the PIOL at each point and the capsule. The coding can be a shading in which the darkness indicates the depth or a color in which different colors indicate different separations to provide the third dimension.

[0030] In another aspect, the software also provides the user with a cross-sectional view of the patient's eye with the projected position and changes that are expected when the PIOL is inserted. Such a display is similar to that shown in Figure 2, showing changes such as the vault of the PIOL over the crystalline lens 20 and the changes in the anterior chamber angle 16, details of which will not be discussed in more detail here.

[0031] In general, there are a plurality of different lens sizes available. In addition, the mechanical properties of the lenses depend on the type of vision correction prescription and the degree of compression in the lens when the lens inserted between the ciliary body, zolular or sulcus limits. For each size lens, the present invention uses the measured distance between the posterior chamber dimensions and the mechanical properties of the lens to predict the three-dimensional configuration of the implanted lens when that lens is placed between the zonular, ciliary body or sulcus points. From this configuration and measurements of the surface of the patient's natural lens, the imaging system generates a map of the predicted modelled distance between the calculated implant lens and the patient's lens. In addition, the imaging system generates a representation of the way the vault of the PIOL pushes the iris forward and hence how it narrows the angle of that particular eye based on the force with which the PIOL acts given its properties and the compression of the PIOL when fitted into the posterior chamber of the eye. The imaging system also generates a representation of where the feet of the PIOL will be pressed whether onto the zonular, ciliary body or sulcus areas. The physician can then select the best predicted fit for the patient.

[0032] In another aspect of the invention, the patient's eyes are also scanned post- operatively using an ultrasound or other imaginer to determine the achieved posterior chamber relations of the PIOL and the eye’s anatomy to determine if the implanted lens is properly positioned and conforms to the predicted configuration or a clinically acceptable configuration. Ideally, all of the PIOL feet contact the ciliary body and sulcus such that the undersurface of the PIOL lens is separated from the patient's own lens and the axis of the lens is correcting the astigmatism of the eye. If not all of the feet are properly placed, the plane of the PIOL can be tilted. In addition, it the case of a toric PIOL, the orientation of the lens relative to the cornea must also be correct. If post-implant scans detect these types of problems, adjustments to the lens position can be made without removing the PIOL, which is a much higher risk operation than exchanging the lens on the assumption that the positioning was correct and that the lens size was incorrect.

[0033] During an ultrasound or other scan, the patient's eye must be still so that the results of various scan lines can be combined. Hence, it is advantageous to provide a scan pattern that requires the fewest scan lines sufficient to arrive at measurements of centration position and axial orientation of the PIOL. Refer now to Figure 6, which illustrates a top view of a PIOL 61 that has been implanted in an eye 62. To locate the edges of the PIOL, scans along lines 71-74 are performed and 6 points of the edges of PIOL 61 are determined as shown at 61-66. These 6 points are used to compute the long axis orientation of the PIOL and hence the orientation of the two scans that will pass through the feet, as shown at 75 and 76. Next, two scans are performed along lines 75 and 76 along the axis of the feet to determine the position of the feet of PIOL 61 within the posterior chamber. If the feet are not all at the same height, the position of PIOL 61 may need to be altered, as PIOL 61 is tilted. Similarly, if the axis if the line through points 63-64 is not parallel to line 72 and PIOL 61 is a toric lens, PIOL 61 may need to be rotated about the intersection of lines 72 and 74 to adjust the astigmatism correction.

[0034] As noted above, the present invention depends on the ability to predict the confirmation of the implanted PIOL prior to implantation. The measured parameters include anatomical measurements made with an ultrasound or other scanner and the scotopic pupil diameter (SPD). Refer now to Figure 7, which illustrates the parameters that are measured with the ultrasound scanner. It should be noted that the eye is relatively spherical, and hence, many of the structures are circular or elliptical in conformation.

[0035] One easily identifiable "landmark" is the sulcus. The plane 35 passing through the sulcus is used to define three measurements of interest. The sulcus-to-sulcus distance (STS) is shown at 34. This is essentially the diameter of the ring of the sulcus in the region in which the PIOL is to be implanted. The maximum distance 32 from the plane defined by the sulcus to the anterior edge of the capsule will be referred to as the STSL. The distance 31 from the capsule to the anterior portion of the cornea will be referred to as the anterior chamber depth (ACD). The diameter 33 of the plane passing through the ciliary body where the ciliary body domes inwards furthest is called the ciliary body inner diameter or CBID, and this is also predictive.

[0036] In addition to the parameters that depend on behind the iris imaging, it has been found that the SPD has predicative value in determining the vault or finding a lens size that provides the desired vault. The SPD is the diameter of the pupil under scotopic light conditions, and is related to PIOL vault due to the difference in force exerted by the iris onto the PIOL for small and large pupils in the physiological state. The pupil size varies according to lighting conditions such that in bright light the pupil constricts and in dim light it dilates. Therefore, depending on lighting conditions and according to how lighting changes during the day the pupil size will be different and produce a specific change in the separation between the PIOL and the crystalline lens. Scotopic pupil size is defined as the pupil diameter under scotopic lighting conditions, defined as ambient 0.04 lux. Other definitions of scotopic lighting conditions exist and by extension will be predictive of PIOL fit. In addition, the lens size and PIOL power need to be taken into account. The lens size is the diagonal diameter of the lens to the tip of the haptics. A recommended PIOL lens size is provided by the lens manufacturer. The PIOL power is related to the curvature of the optical central inner and outer surface of the PIOL. For example, a high powered myopic lens will have an increased radius of curvature of the back surface of the lens resulting in a higher central vault compared to a lower powered lens. PIOL. The PIOL power is also related to the thickness profile of the PIOL, and therefore, PIOLs with different powers react differently when forces are applied. Therefore PIOLs having different powers (assuming all other conditions are identical) will result in different vault outcomes.

[0037] The parameters CBID, SPD, STS and STSL will be referred to as the anatomical parameters in the following discussion. The parameters PIOL power and PIOL size will be referred to as the target PIOL parameters.

[0038] In one aspect of the invention, a model that depends on the anatomical parameters, the target PIOL parameters and a set of unknown parameters is trained by fitting a data set derived by measuring a number of different patients before and after PIOL implants. In the training mode, a prior art system for predicting the vault is utilized to minimize the risk of an improperly sized PIOL being implanted into a patient. Once a data set with sufficient statistical accuracy to provide improved accuracy is accumulated, the improvement available with the present system can be realized.

[0039] One exemplary model relates the vault of the PIOL to a linear function of the above parameters, e.g.

Predicated Vault = a*CBID + b*STSL + c*(PIOL Power) + d*(PIOL size) + e*SPD The parameters a-e are determined by fitting the observed vault values in the patient group.

[0040] The above-described linear model is only one exemplary model that can be used to model the dependence of the vault on the anatomical parameters. For example nonlinear models such as polynomial, exponential, expert parameter cost-center weighting systems or neuro-networks can be trained to provide the vault prediction.

[0041] Refer now to Figure 5, which illustrates one embodiment of an imaging system according to the present disclosure. In system 40, the imaging device forms the images of the patient's eyes using ultrasound or other imaging device 42 that is coupled to the patient's eye by patient interface 41. The recorded image is processed by controller 43, which extracts the anatomical measurements that depend on the ultrasound or other image.

A user interface 44 allows a user to input additional information such as the PIOL power and possible sizes to controller 43. Controller 43 computes the predicted vault for each lens size requested by the user. A three-dimensional map of the distance between the crystalline lens capsule and the predicted PIOL configuration is then displayed on a display 45.

[0042] As noted above, the data processing functions of controller 43 can be implemented on a separate data processing system which is adapted to receive ultrasound or other images from a separate ultrasound or other imaging device. A user interface of that separate data processing system can be used for inputting the lens properties and outputting the predicted vaults for each desired lens size. [0043] In another aspect, a fitting system according to the present invention provides a warning if a physician is trying to achieve a vault that is outside a predetermined range by using a large PIOL in an eye with too small of internal posterior chamber dimensions. Refer now to Figures 8A-8E, which illustrate the manner in which the vault changes with the CBID and posterior chamber dimensions. Each figure shows a cross-section of a PIOL that is implanted in an eye with particular CBID and posterior chamber dimensions. The "feet" of the PIOL are shown at 81 in Figure 8 A. The region 82 between the feet and the lens is commonly referred to as the haptic of the lens, but will be referred to as the legs in the following discussion. Assume that the vault for the configuration shown in Figure 8A is V. Over the useful range of the PIOL, the legs are concave upwards as shown in Figure 8A. As the feet are moved closer together, i.e., the lens is placed in a smaller eye, the vault increase. The amount of increase for a particular change, x, in the spacing will be referred to as "a".

The vault for the change of x between the configurations shown in Figures 8A and 8B is approximately V+a as shown in Figure 8B. If the feet are moved even closer together by x, i.e., an even smaller eye, vault increases in a predictable way based on the particularly mechanics of the PIOL to approximately V+2a as sown in Figure 8C. Similarly, the vault can be increased to V+3a as shown in Figure 8D by moving the feet closer together by the same amount. It should be noted that the legs remain concave upward as the vault increases by the amounts illustrated in Figures 8A-8D.

[0044] In essence, a physician may wish to have an implant with a very high vault in an eye that possesses dimensions including a very high STSL and could, in principle, use a larger lens, which will be forced to have its feet closer together than a smaller lens. This type of fit might be preferable for a young patient to provide more room for the natural crystalline lens grow with aging. However, it has been found experimentally that there is a limit to ability to increase vault by increasing the size of the PIOL. At some point, the legs of the PIOL become concave downward as shown in Figure 8E, and the vault "jumps" by a much higher increment than expected based on the relationship described above between the vault V and the relative approximation x as described above. This secondary mechanical behavior of the PIOL would lead to an excessively high value of vault. For example, rather than obtaining a vault of V+4a if approximating by 4x, the implant could have a vault of V+6a when inserted in the patient's eye, even though predicted to have a vault of 4a, which will be excessive. In this case, the PIOL may need to be explanted and/or exchanged. As noted above, such exchanges are, in general, to be avoided as they involve further risk to the health of the eye.

[0045] The point at which the configuration of the legs changes from concave upward to concave downward will be referred to as the flip point. The flip point is a function of the particular PIOL material, size, and prescription. In one aspect of the invention, the operating system warns the physician of the possibility of flipping for each of the PIOL sizes that are close to the flipping point for the patient in question. The cross-sectional display discussed above can also show the flipped version of the PIOL and the excessive vault.

[0046] The present invention also includes a computer readable medium that stores instructions that cause a data processing system to execute the method of the present invention. A computer readable medium is defined to be any medium that constitutes patentable subject matter under 35 U.S.C. 101 and excludes any medium that does not constitute patentable subject matter under 35 U.S.C. 101. Examples of such media include non-transitory media such as computer memory devices that store information in a format that is readable by a computer or data processing system.

[0047] The above-described embodiments of the present invention have been provided to illustrate various aspects of the invention. However, it is to be understood that different aspects of the present invention that are shown in different specific embodiments can be combined to provide other embodiments of the present invention. In addition, various modifications to the present invention will become apparent from the foregoing description and accompanying drawings. Accordingly, the present invention is to be limited solely by the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method for operating an imaging system, said method comprising generating an estimate of a position of a PIOL that corrects a vision deficit in a patient's eye from anatomical parameters describing said patient's eye, said PIOL having a particular size; and generating a three-dimensional graphical representation of a distance between a back surface of said PIOL and a crystalline lens of said patient's eye and displaying said three- dimensional graphical representation on a display controlled by said imaging system.

2. The method of Claim 1 wherein said anatomical parameters are measured by said imaging system.

3. The method of Claim 1 wherein said imaging system is an ultrasound imaging system adapted for scanning a patient's eye.

4. The method of Claim 1 wherein said method is repeated for different size PIOLs.

5. The method of Claim 1 further comprising generating a cross-sectional view of said patient's eye showing said estimated position of said PIOL and a surface of said patient's crystalline lens.

6. The method of Claim 5 wherein said cross-sectional view further comprises an estimated position of the iris of said patient's eye after said PIOL has been implanted.

7. An imaging system comprising: a measurement assembly; a display; and a controller, said controller being adapted to measure anatomical parameters describing a patient's eye using said measurement assembly, to generate an estimate of a position of a PIOL having a particular size that corrects a vision deficit in a patient's eye from said anatomical parameters, and to generate a three-dimensional graphical representation of a distance between a back surface of said PIOL and a crystalline lens of said patient's eye, and displaying said three-dimensional graphical representation on said display.

8. The imaging system of Claim 7 wherein said measurement assembly comprises an ultrasound imaging system adapted for scanning a patient's eye.

9. The imaging system of Claim 7 wherein said controller generates said three- dimensional graphical representation for a plurality of different PIOL sizes.

10. The imaging system of Claim 7 wherein said controller generates a cross- sectional view of said patient's eye showing said estimated position of said PIOL and a surface of said patient's crystalline lens.

11. The imaging system of Claim 10 wherein said cross-sectional view further comprises an estimated position of the iris of said patient's eye after said PIOL has been implanted.