Progressive Addition Lens Refractive Power Optimization
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Solution Overview
Problem
Current ophthalmic progressive addition lenses for presbyopic wearers do not adequately enhance visual comfort, particularly for visual tasks at close distances due to limitations in refractive power distribution and astigmatism management.
Innovation Solution
A method involving computer-aided design to calculate and optimize the mean refractive power distribution and astigmatism repartition across the lens, ensuring specific criteria are met to enhance visual comfort, including defining a threshold criterion (CRIT) and optimizing angular zones for reduced acuity loss, thereby improving visual performance at distances of 70 cm and less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional progressive addition lenses are used, then the lens can provide basic refractive correction, but visual comfort for close visual tasks is insufficient due to inadequate refractive power distribution and astigmatism management
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive power distribution across the lens surface, specifically adjusting the progression of refractive power from the upper to lower zones. The method calculates optimal lowering angles (a60%, a85%, a100%) where specific percentages of the prescribed addition are perceived, and adjusts these parameters to satisfy the CRIT criterion (0.38 ≤ CRIT ≤ 4.50). This systematic parameter optimization resolves the contradiction by achieving precise refractive power distribution that enhances visual comfort for close tasks while maintaining manufacturing feasibility through computer-aided design.
Solution Approach 2:
The patent implements local quality by creating zone-specific refractive power characteristics. The lens is divided into functional zones (upper zone for distance vision, lower zone for near vision, and intermediate zones) with distinct refractive power properties. The method defines specific lowering angles (a60%, a85%, a100%) that correspond to different visual task requirements, allowing each zone to be optimized for its specific function. This local optimization ensures that refractive power distribution matches the actual visual needs at different distances, thereby improving visual comfort without compromising manufacturing precision.
2Reliability
If the refractive power is optimized for close vision, then visual comfort at 70 cm and less improves, but the lens design complexity increases due to multiple criteria calculations
Solution Approach 1:
The patent applies feedback by implementing an iterative optimization process where the lens design is evaluated against multiple criteria (CRIT, LAcuSub60_85, LAcuSub60_85) and adjusted accordingly. The method calculates the criterion values based on the refractive power distribution and lowering angles, then uses these feedback results to refine the lens design. This feedback mechanism allows the system to automatically adjust parameters to satisfy the required visual comfort for close tasks while managing design complexity through algorithmic optimization rather than manual trial-and-error.
Solution Approach 2:
The patent implements preliminary action by performing computer-aided design calculations before actual lens manufacturing. The method preliminarily determines optimal lowering angles, refractive power distributions, and astigmatism corrections through virtual modeling and simulation. By conducting these complex calculations and optimizations in the design phase rather than during manufacturing, the system prepares all necessary parameters in advance, reducing the complexity of the actual manufacturing process while ensuring visual comfort for close tasks is achieved.
3Manufacturing precision
If multiple optimization criteria are applied, then visual performance at close distances improves, but the calculation and design process becomes more complex
Solution Approach 1:
The patent applies mechanics substitution by replacing manual optical design methods with computer-aided design and simulation systems. Instead of relying on traditional mechanical trial-and-error approaches or manual calculations, the method uses computational algorithms to simulate lens performance, calculate refractive power distributions, and optimize visual performance. This substitution of mechanical/manual processes with digital/computational methods significantly reduces the complexity of the design process while maintaining high precision in achieving visual performance goals for close tasks.
Data Source
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AI summary
An ophthalmic progressive addition lens for a presbyopic wearer which has a prescribed far vision mean refractive power a non nil prescribed addition, ADDP, said lens having a far vision reference point, a mean refractive power, ΡΡΟ(α, β), a module of resulting astigmatism, ASR(a, β), a meridian line, ML(a, β), said (α, β) functions being determined in as-worn conditions of the lens by the wearer for gaze directions (α, β) joining the center of rotation of the eye, CRE, and the lens, where a is a lowering angle in degree and β is an azimuth angle in degree, and wherein a lens criterion, CRIT, fulfils following requirement: 0.38 ≤ CRIT ≤ 4.50, where: • CRIT = NumeratorCRIT / DenominatorCRIT; • NumeratorCRIT = (A1 /A2) + (PPO(αFV, βFV)/ (100.ADDP)); A1 = α100% - α85%; A2 = α100% - α60%; • DenominatorCRIT = [(PeaksMean/ADDp)+(PPO(αFVβFV)/(8.ADDp))]3.