Non-Round Soft Contact Lens Eyelid Interaction Design
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Solution Overview
Problem
Existing contact lens designs fail to maintain optimal orientation and centration on the eye due to rotational instability caused by eyelid movement during blinking, as they do not effectively utilize the geometry of the upper and lower eyelids to adjust the lens's outer contour for improved stability and rotation.
Innovation Solution
A method for designing non-round soft contact lenses that optimizes the variation of lens-lid contact area by maximizing the difference between the contact area when the lens is mis-oriented and correctly oriented, using finite element analysis and custom or population-average eyelid geometries to tailor the lens shape for improved centration and rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional round contact lens design is used, then manufacturing simplicity is maintained, but lens stability and rotation control on the eye deteriorates
Solution Approach 1:
The patent applies asymmetry by transitioning from traditional round (symmetrical) contact lens designs to non-round lens contours. The outer contour is specifically designed with asymmetric geometry that interacts differently with the upper and lower eyelids, creating unequal contact areas that generate stabilizing forces to control lens rotation and maintain proper orientation on the eye.
2Stability of the object's composition
If mechanical stabilization features are added to maintain lens orientation, then lens orientation stability is improved, but device complexity increases
Solution Approach 1:
The patent uses asymmetric outer contour design as a simpler alternative to complex mechanical stabilization features. Instead of adding multiple thick/thin zones, depressions, elevations, or truncations, the solution achieves orientation stability through the geometric asymmetry of the lens periphery itself, which naturally interacts with eyelid forces to maintain proper lens orientation.
3Stability of the object's composition
If symmetric thick and thin zones are used for dynamic stabilization, then lens rotation control is improved, but lens centration and orientation accuracy deteriorates due to asymmetric eyelid contact
Solution Approach 1:
The patent recognizes that symmetric stabilization zones create asymmetric contact with the naturally asymmetric upper and lower eyelids, leading to unintended lens tilting. The solution is to design the outer contour itself with asymmetric geometry that matches the asymmetric eyelid geometry, creating balanced and predictable lens-eyelid interactions that simultaneously control rotation and maintain accurate centration.
Solution Approach 2:
The patent applies local quality by designing different regions of the lens periphery with specific geometric characteristics tailored to interact with the upper and lower eyelids. The outer contour is optimized in specific locations to create appropriate contact areas with each eyelid, allowing differential control of lens position and orientation based on local geometric properties rather than uniform symmetric design.
4Stability of the object's composition
If non-round lens design is implemented, then lens stability and rotation control are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements asymmetric non-round lens designs with optimized outer contours that require precise manufacturing to achieve the intended asymmetric geometry. The manufacturing process must accurately produce the specific asymmetric shape to ensure proper interaction with eyelids and achieve the desired stabilization effect, thereby increasing precision requirements compared to simple round lenses.
Data Source
AI summary
A method for optimizing the performance in centration, rotation and stability of contact lenses makes use of the upper and lower eyelid geometries to maximize the lens-lid interaction for two different contact lens positions on the eye. The contact lenses are non-round lenses for maximum interaction with the eyelids.