Contact Lens Rear Surface Fitting Using Zernike Polynomials
Solution Overview
Problem
Current contact lens manufacturing methods struggle to achieve high precision and comfort by accurately reflecting the individual's corneal shape, especially due to the complexity and variability of human corneal surfaces, leading to issues like discomfort and displacement during wear.
Innovation Solution
A contact lens manufacturing method that utilizes statistical information of a population's corneal surface shape, combining rotationally symmetrical and rotationally asymmetric shapes using Zernike polynomials to define the lens rear surface, allowing for efficient and precise fitting by averaging and standard deviation calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If made-to-order contact lenses are manufactured using individual corneal surface measurements, then the shape fitting precision is improved, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent uses statistical average corneal surface data from a population as a representative model (copy) instead of requiring individual measurements for each lens. This copying approach captures the essential characteristics of corneal surfaces while avoiding the complexity of custom manufacturing for each patient.
Solution Approach 2:
The patent transforms the complex individualized manufacturing approach into a standardized parameter-based system using statistical averages (mean radius of curvature, mean base curve) and standard deviations. This parameter transformation simplifies the manufacturing process while maintaining adequate precision for the peripheral zone.
2Measurement precision
If complex mathematical notation is used to represent corneal surface shape, then the shape representation precision is improved, but the processing difficulty and time increase
Solution Approach 1:
The patent extracts only the essential parameters (radius of curvature, base curve, standard deviation) from the complex corneal surface data, separating the critical fitting parameters from the unnecessary mathematical complexity. This extraction enables practical manufacturing while maintaining adequate precision.
Solution Approach 2:
The patent applies partial action by using simplified mathematical representations (mean values and standard deviations) rather than complete individualized mathematical models. This partial approach provides sufficient precision for the peripheral zone without requiring excessive processing time and complexity.
3Ease of manufacture
If standard base curve settings are used, then the manufacturing ease is improved, but the wearing comfort decreases due to poor shape matching
Solution Approach 1:
The patent applies local quality by differentiating the shape requirements between the optical zone and peripheral zone. The peripheral zone uses statistical average parameters optimized for corneal matching, while the optical zone maintains standard manufacturing practices. This localized approach improves wearing comfort without compromising manufacturing ease.
Data Source
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AI summary
The purpose of the present invention is to provide novel contact lens manufacturing method and contact lens capable of giving a lens inner surface shape reflecting a cornea shape of a contact lens wearer more easily than before with sufficient accuracy to reflect the cornea shape, thereby improving comfort during use. By using statistical information on a corneal surface shape obtained from a population of target eyes having a feature to be treated, a fitting for a rotationally-symmetric shape is performed based on a definitional equation using a radius of curvature (R) and a conic constant (C.C.) while a fitting for a rotationally-asymmetric shape is performed based on a definitional equation using a Zernike function. A shape of a lens rear surface (20) corresponding to the corneal surface shape specified by these definitional equations is adopted for a rear surface of a peripheral area of a contact lens (10).