Pupil-Dependent Wavefront Refraction for Ophthalmic Prescription
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Solution Overview
Problem
Conventional methods for determining ophthalmic prescriptions (Rx) only account for a single fixed pupil size, which limits their effectiveness in correcting vision defects across varying pupil diameters, leading to ambiguity and non-optimal results due to multiple local extrema in the merit function.
Innovation Solution
The method involves searching a multi-dimensional parameter space for optimal Rx values at multiple pupil sizes, starting from the smallest pupil size and tracking extremum movements as the aperture increases, while accounting for physiological aspects like the Stiles-Crawford effect and preferential axis orientations, to determine a final Rx that provides effective vision correction across a range of pupil diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional methods calculate Rx based on a single fixed pupil size, then the calculation process is simple, but the vision correction effectiveness deteriorates across varying pupil diameters
Solution Approach 1:
The patent segments the pupil size range into multiple discrete sizes (e.g., 1mm, 2mm, 3mm, 4mm diameters). For each pupil size, a separate wavefront measurement and Rx optimization is performed, creating pupil-size-specific correction parameters. This segmentation allows the system to account for varying optical performance across different pupil conditions without overwhelming computational complexity.
Solution Approach 2:
The patent implements a dynamic tracking approach where the optimal Rx parameters are followed as the pupil size changes. Starting from a small pupil size where the optimum is unique, the method tracks how the extremum moves in Rx space as the aperture increases. This dynamic adaptation ensures the correction remains optimal across varying physiological conditions.
2Reliability
If multiple pupil sizes are considered in Rx determination, then vision correction effectiveness improves across varying pupil diameters, but the calculation complexity increases
Solution Approach 1:
The patent performs preliminary wavefront measurements at multiple pupil sizes before final Rx determination. By pre-characterizing the optical system at different aperture conditions, the subsequent optimization process can efficiently combine these measurements. The method also performs preliminary tracking from small to large pupil sizes to identify the correct extremum path, avoiding computationally expensive exhaustive searches.
Solution Approach 2:
The patent employs feedback mechanisms where wavefront measurements taken at different pupil sizes inform and refine the Rx optimization. The measured wavefront aberrations serve as feedback to adjust the correction parameters, ensuring the final Rx accounts for actual optical performance across the pupil size range. This feedback loop validates and refines the multi-size optimization results.
3Measurement precision
If the merit function has multiple local extrema, then finding the optimal Rx becomes ambiguous, but searching the entire parameter space increases computational time
Solution Approach 1:
The patent performs preliminary optimization at small pupil sizes where the merit function typically has a unique, well-defined extremum. This preliminary result serves as a reliable starting point for tracking to larger pupil sizes. By establishing the correct extremum early in the process, the method avoids getting trapped in local minima at larger apertures without requiring exhaustive searches of the entire parameter space.
Solution Approach 2:
The patent implements dynamic tracking of the extremum position as pupil size increases. Rather than performing static, independent optimizations at each aperture, the method continuously follows how the optimal parameters evolve with changing pupil diameter. This dynamic approach efficiently navigates through the parameter space by leveraging the continuity of optical behavior, significantly reducing computational time compared to exhaustive searches.
4Ease of manufacture
If wavefront aberration is measured for a large pupil, then measurement accuracy for small pupils can be obtained by mathematical cropping, but measuring for multiple pupil sizes provides more accurate results
Solution Approach 1:
The patent makes the wavefront measurement system universal by capable of measuring at multiple pupil sizes using the same optical apparatus. Rather than requiring different measurement setups for different apertures, the system can directly measure wavefront aberrations at various pupil diameters (e.g., 1mm, 2mm, 3mm, 4mm) using identical hardware, simplifying the measurement process while maintaining high accuracy.
Solution Approach 2:
The patent creates accurate copies of the wavefront aberration characteristics at different pupil sizes through direct measurement. Rather than mathematically cropping or approximating from a single large-pupil measurement, the system directly captures the true wavefront behavior at each aperture condition, providing authentic optical data that cannot be perfectly replicated through mathematical operations alone.
Data Source
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AI summary
A method of determining an ophthalmic prescription (Rx) for a patient's eye, includes obtaining a wavefront measurement of the patient's eye; determining a first Rx for the patient's eye from the wavefront measurement, the first Rx corresponding to a maximum value of a merit function calculated from the wavefront measurement of the patient's eye for a first size of the pupil of the patient's eye; determining one or more additional Rx's of the patient's eye for one or more additional pupil sizes different from the first pupil size, wherein each additional Rx is determined for a corresponding size by calculating a value of the merit function for the previously-calculated Rx at the corresponding size and searching for an Rx at the corresponding size that provides a larger value of the merit function than the previously-calculated Rx at the corresponding size; determining a final Rx based on the first Rx and the additional Rx's; and outputting the final Rx.