Progressive Ophthalmic Lens Aberration Control
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Solution Overview
Problem
Progressive multifocal ophthalmic lenses often suffer from optical aberrations such as spherical aberration and coma, which affect visual acuity and accessibility to different vision zones, particularly in presbyopic wearers who require varying power corrections for distance and near vision.
Innovation Solution
A progressive multifocal ophthalmic lens with a complex surface design that includes a distance vision zone, near vision zone, and intermediate vision zone, featuring a main progression meridian, optimized to minimize optical aberrations by adjusting the radii of curvature and ensuring a reduced root mean square deviation of less than 0.025 micrometers per diopter over a specific angular sector, thereby enhancing visual acuity and accessibility to necessary powers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If progressive multifocal lenses are designed with complex surface optimization to minimize optical aberrations, then visual acuity in distance vision is improved, but the complexity of lens manufacturing and surface definition increases
Solution Approach 1:
The patent applies parameter changes by optimizing the radii of curvature of the front and/or rear lens surfaces at multiple zones (distance vision zone, intermediate vision zone, near vision zone) to minimize optical aberrations. The invention defines specific parameter ranges for radii of curvature (R1, R2, R3, R4) and their relationships to achieve reduced root mean square deviation while maintaining manufacturability through systematic parameter optimization rather than arbitrary complex surface design
Solution Approach 2:
The patent segments the lens into distinct functional zones (distance vision zone, intermediate vision zone, near vision zone) with specific optimization criteria for each zone. This segmentation allows different surface characteristics to be optimized for different viewing distances, improving overall visual acuity across all zones while managing complexity through structured zonal optimization rather than uniform complex surface design
2Area of stationary object
If the radii of curvature are adjusted to reduce optical aberrations over a wide angular sector, then the field of view in distance vision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies partial action by optimizing optical performance over a specific angular sector (with apex at 4° below the mounting cross and angular opening between 150° and 160°) rather than attempting to optimize the entire 360° field. This partial optimization approach achieves improved visual acuity over the clinically relevant viewing angles while maintaining reasonable manufacturing precision requirements by not demanding perfection across all possible angles
3Ease of operation
If the lens is optimized for presbyopic wearers with specific mounting conditions (27mm vertex distance, 8° pantoscopic angle), then accessibility to near vision powers is improved, but the lens design becomes more specific and less adaptable to different wearing conditions
Solution Approach 1:
The patent applies preliminary action by pre-optimizing the lens surface radii of curvature for specific presbyopic wearing conditions (27mm vertex distance, 8° pantoscopic angle, 0° curvature) before the lens is mounted. This preliminary optimization ensures that the lens delivers the intended optical performance and near vision accessibility when worn according to standard fitting protocols, while the systematic parameter definitions allow for reasonable adaptability to slight variations in wearing conditions
Data Source
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AI summary
The lens has a power addition prescription and a complex surface presented with a fitting cross. A far vision zone has a control point, and a near vision zone has a control point and an intermediate vision zone. A principal meridian of progression passes via the three zones. A reduced root mean square deviation is normalized to the addition prescription of less than a specific decimal value of microns per dioptre over a zone that includes the far vision control point. A progression length is defined as an angle of lowered viewing from the fitting cross down to the point on the meridian. An independent claim is also included for a method of correcting the vision of a presbyopic subject.