Segmented Composite Lens Design for Hybrid Contact Lenses
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Solution Overview
Problem
Conventional hybrid lenses face issues such as lens flexure, scleral impingement, tear stagnation, and difficulty in removal due to adherence, primarily caused by the separation and bonding of materials at the radial junction, leading to optical distortions and material expansion-related stresses.
Innovation Solution
A composite lens design featuring an anterior rigid gas permeable layer with a segmented or non-segmented annulus of soft material bonded to its posterior surface, providing a central rigid zone and a peripheral zone that is generally rigid anteriorly and soft posteriorly, which allows for tear exchange, reduces flexure, and facilitates lens removal by relieving surface attraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If soft material is bonded to rigid material in the optic zone, then comfort is improved, but optical integrity deteriorates due to irregularities and distortion
Solution Approach 1:
The lens is divided into two distinct zones: a central optic zone with rigid material for optical clarity and a peripheral zone with soft material for comfort. This segmentation prevents soft material from interfering with the optic zone while maintaining both optical integrity and comfort benefits
Solution Approach 2:
Different regions of the lens are assigned different material properties: the central region uses rigid gas permeable material optimized for optics, while the peripheral region uses soft hydrogel material optimized for comfort. Each zone's material is specifically tailored to its functional requirements
2Ease of operation
If soft material is used in the corneal portion, then comfort is improved, but tear exchange deteriorates due to circumferential sealing
Solution Approach 1:
The soft material is confined to a peripheral annular zone rather than extending to the center, creating a natural gap at the junction between soft and rigid zones that allows tear exchange while maintaining peripheral comfort
3Strength
If radial junction bonding is used, then structural integrity is improved, but lens flexure and separation worsen
Solution Approach 1:
By separating the soft and rigid zones into distinct central and peripheral regions, the design eliminates the radial junction problems associated with conventional hybrid lenses. The zones are joined at a circumferential interface that prevents separation and flexure while maintaining structural integrity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enhances comfort and stability by managing flexure and air bubbles, ensuring proper tear exchange and rotational stability, while preventing optical distortions and adherence issues, thus improving the overall fit and usability of the lens.
Implementation Method 1
the expansion of the soft material upon hydration of as little as 1% is known to create stresses at the surface which stimulate optical distortion
Implementation Method 2
the segmentation of the annulus serves as a relief for undesired expansion of the soft material on hydration, and prevents buckling or surface distortion due to expansion
Data Source
AI summary
A composite lens comprises an anterior rigid gas permeable layer, and an annulus of soft material bonded to a posterior surface of the anterior rigid gas permeable layer, wherein a central zone of the composite lens is rigid and without a soft layer, wherein a peripheral zone of the composite lens is generally rigid in its anterior aspect and soft in its posterior aspect.