EP-4735857-A1 - METHOD FOR QUANTITATIVE EVALUATION OF CONTACT LENS EDGE LIFT BASED ON OCT IMAGES

Abstract

A method for quantitively evaluating contact lens edge lift and distortion. The method includes the steps of scanning an edge of a contact lens, modeling the edge profile, determining a best-fit line over the modeled edge profile, calculating the slope of the best-fit line at a contact lens edge point, and further calculating a slope edge angle (ESA) as a function of the slope, wherein the ESA is a highly effective metric for capturing the contact lens edge-lift relative to the intended shape of the lens. The method may be used to provide design feedback, predict clinical fitting outcomes, and for quality control purposes.

Inventors

• GU, YEMING
• WANG, YAN
• HOSSEINI, SEYEDHADI

Assignees

• Alcon Inc.

Dates

Publication Date

20260506

Application Date

20240627

Claims (20)

1. 1. A method of evaluating a lens having a posterior surface, an anterior surface, and an axial axis, the method comprising the steps of: collecting an image of an edge of the lens; modeling a profile of the lens from the image; processing the model of the profile; and conducting a quantitative analysis of the profile.
2. 2. The method of Claim 1 , further comprising the step of repeating the steps of the method at a plurality of points along the periphery of the lens.
3. 3. The method of Claim 2, further comprising the step of generating a comprehensive diagram including the results of the quantitative analysis conducted at the plurality of points.
4. 4. The method of Claim 3, wherein the points are equally spaced from one another.
5. 5. The method of Claim 4, wherein the points are spaced about 15 degrees apart.
6. 6. The method of Claim 1 , wherein the step of processing the model of the profile comprises approximating a best-fit line for the profile.
7. 7. The method of Claim 6, wherein the best-fit line is defined by a linear function.
8. 8. The method of Claim 6, wherein the best-fit line is defined by a polynomial function.
9. 9. The method of Claim 8, wherein the best-fit line is defined by a third-order polynomial function.
10. 10. The method of Claim 8, wherein the step of conducting the quantitative analysis of the profile comprises determining a slope edge angle.
11. 11. The method of Claim 10, wherein the slope edge angle is a function of the slope of the best-fit line at the edge of the lens.
12. 12. The method of Claim 1 , wherein the image of the edge of the lens is collected with a scanning system.
13. 13. The method of Claim 12, wherein the scanning system comprises an optical coherence tomographer and a cuvette for holding the lens, wherein the optical coherence tomographer is coaxially aligned to the lens and the optical coherence tomographer is configured to rotate about the axial axis of the lens and capture images of the edge of the lens.
14. 14. The method of Claim 13, wherein the optical coherence tomographer is a lens edge optical coherence tomographer.
15. 15. The method of Claim 14, further comprising the step of correcting the image of the edge of the lens accounting for effects of refractive index and aspect ratio.
16. 16. The method of Claim 1 , wherein the step of modeling the profile of the lens comprises modeling the profile of at least one of the base curve surface or the front curve surface of the lens.
17. 17. A system for determining quantitative measurements of a contact lens edge, comprising: means for imaging a cross-sectional profile of the contact lens edge; means for determining a regression curve for the cross-sectional profile; and means for determining the quantitative measurements of the contact lens edge along a periphery of the contact lens.
18. 18. The system of Claim 17, wherein the means for imaging the cross-sectional profile comprises an optical coherence tomographer.
19. 19. The system of Claim 18, wherein the means for imaging the cross-sectional profile further comprises a receptacle for temporarily holding the contact lens securely in place and the optical coherence tomographer is configured to rotate relative to the contact lens.
20. 20. The system of Claim 17, wherein the quantitative measurements comprise edge slope angles for identifying edge distortion along the contact lens edge.

Description

METHOD FOR QUANTITATIVE EVALUATION OF CONTACT LENS EDGE LIFT BASED ON OCT IMAGES Technical Field [0001] The present invention relates generally to the field of contact lenses, and more particularly to a method of quantitively evaluating contact lens edge lift based on optical coherence tomography (OCT) imaging. Background [0002] The exact shape of a contact lens, especially the shape of the lens edge, is important to on-eye fitting and comfort. Traditional methods for evaluating lens shape are typically crude and lack in details (such as various methods for measuring sag and base curve radius or base curve equivalent). Destructive methods such as lens cross-section are used to examine the details of lens edge distortion; however, such methods cannot provide true-form shape evaluations. Non-destructive crosssection imaging methods enabled by optical coherence tomography (OCT) technology have also been used, but such methods are used mostly for qualitative evaluation by visually determining features such as for example edge lift and/or edge bending and are not precise. For example, Full Lens OCT (FLO) may be used to capture full lens cross-section images and Lens Edge OCT (LEO) can be used to capture details of lens edges. The cross-section images from both FLO and LEO can be visually inspected for noticeable edge shape distortions, but these evaluations do not provide quantitative measurements. [0003] Accordingly, it can be seen that needs exist for improvements to methods defining various edge distortions quantitatively and precisely with simplicity and practicality. It is to the provision of improvements to a method of evaluating contact lens edge distortion meeting these and other needs that the present invention is primarily directed. Summary [0004] Generally, the present invention provides a simple and practical method of quantitatively gauging edge shape distortion in general and lens edge lift in particular. The method includes measuring the lens edge and determining an edge slope angle (ESA) of the lens edge. The ESA is a highly effective metric for capturing the contact lens edge-lift relative to the intended shape of the lens. Variations of this metric defined over different ranges, or the difference between different ESA models, can capture edge shape distortion on different scale and in meaningful details. The evaluation method of the present invention, and the resulting metrics, can be used for example to provide design feedback for lens design iteration process, predict clinical fitting outcomes, as a tool for process investigation related to lens edge quality, and as a quality control metric for controlling edge lift. [0005] In one aspect, the present invention relates to a method of evaluating a lens having a posterior surface, an anterior surface, and a central axis. The method includes the steps of (i) collecting or capturing an image of an edge of the lens; (ii) modeling a profile of the lens from the image; (iii) processing the model of the profile; and (iv) conducting a quantitative analysis of the profile model. [0006] In some example embodiments, the method may further comprise the step of repeating the steps of the method at a plurality of points along the periphery of the lens. The method may still further comprise the step of generating a comprehensive diagram or graph including the results of the quantitative analysis conducted at each of the plurality of points. The points may be intermittently or equally spaced from one another, such as for example 15 degrees between one another. [0007] In some example embodiments, the step of processing the model of the profile may comprise approximating a best-fit line for the profile model. The best-fit line may be defined by a linear or a polynomial function, such as for example a 3rd order polynomial function. In still other example embodiments, the step of conducting the quantitative analysis of the profile may comprise determining a slope edge angle, wherein the slope edge angle is a function of the slope of the best-fit line at the edge of the lens. [0008] In some example embodiments, the image of the lens edge is collected with a scanning system. The scanning system may include an optical coherence tomographer and a cuvette for holding the lens. Preferably, the optical coherence tomographer is coaxially aligned to the lens and the optical coherence tomographer is configured to rotate about the central axis of the lens and capture images of the lens edge. In preferred embodiments, the optical coherence tomographer is a lens edge optical coherence tomographer. [0009] In some example embodiments, the method may further comprise the step of correcting the image of the lens edge accounting for effects of a refractive index and/or aspect ratio. The step of modeling the profile of the lens may comprise modeling the profile of at least one of the anterior surface or the posterior surface of the lens. [0010] In another aspect, the present inv