Silicone Hydrogel Contact Lens Layering for Lubricious Water-Rich Surfaces
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Solution Overview
Problem
Silicone hydrogel contact lenses face challenges with maintaining hydrophilicity, wettability, and lubricity due to silicone migration and high water content leading to dehydration and discomfort, while balancing oxygen permeability and mechanical strength.
Innovation Solution
A layered structural configuration with an anterior and posterior outer hydrogel layer covering a silicone hydrogel inner layer, featuring a water content gradient and specific water-swelling ratios, ensuring high oxygen permeability and biocompatibility, reducing dehydration, and enhancing lubricity and hydrophilicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If water content in silicone hydrogel contact lens is increased to improve comfort and biocompatibility, then lens comfort and biocompatibility are improved, but oxygen permeability is compromised and dehydration increases
Solution Approach 1:
The contact lens is divided into two distinct layers: a silicone hydrogel inner layer providing oxygen permeability and mechanical strength, and a non-silicone hydrogel outer layer providing high water content for comfort. This segmentation allows each layer to independently fulfill its specific function without compromising the other properties.
Solution Approach 2:
Different regions of the contact lens are assigned different water content characteristics. The outer surface layer has high water content (≥50%) for comfort and biocompatibility, while the inner bulk material has lower water content (10-70%) optimized for oxygen permeability. This local differentiation resolves the contradiction between comfort and oxygen transmission.
2Reliability
If silicone is incorporated to achieve high oxygen permeability, then oxygen permeability is improved, but hydrophilicity, wettability, and lubricity deteriorate due to silicone migration
Solution Approach 1:
The contact lens is divided into two distinct layers: a silicone hydrogel inner layer providing oxygen permeability and mechanical strength, and a non-silicone hydrogel outer layer providing high water content for comfort. This segmentation allows each layer to independently fulfill its specific function without compromising the other properties.
Solution Approach 2:
Silicone is extracted from the outer surface layer and confined to the inner bulk material. The outer layer is made completely free of silicone, eliminating the source of silicone migration that causes hydrophobicity. This extraction resolves the contradiction between oxygen permeability (provided by inner layer silicone) and surface hydrophilicity (provided by outer layer absence of silicone).
3Ease of operation
If water content is increased to provide softness and comfort, then initial comfort and adaptability are improved, but mechanical strength and rigidity decrease
Solution Approach 1:
The contact lens is divided into two distinct layers: a silicone hydrogel inner layer providing oxygen permeability and mechanical strength, and a non-silicone hydrogel outer layer providing high water content for comfort. This segmentation allows each layer to independently fulfill its specific function without compromising the other properties.
Solution Approach 2:
The contact lens uses a composite structure combining silicone hydrogel material (providing strength and oxygen permeability) with non-silicone hydrogel material (providing softness and comfort). This composite approach allows the lens to simultaneously achieve mechanical strength and initial comfort that would be difficult to obtain with a single material.
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 solution maintains lens comfort and biocompatibility by minimizing silicone exposure, reducing dehydration, and providing a lubricious surface, while maintaining high oxygen permeability and mechanical strength.
Implementation Method 1
an outer surface layer that has a thickness of about 0.1 to about 20 μm and completely covers the silicone hydrogel bulk material and is made of a hydrogel material totally or substantially free of silicone and having a higher water content characterized by a water-swelling ratio of at least about 100%
Implementation Method 2
it is believed that in-eye dehydration may be derived from evaporation (i.e., water loss) at the anterior surface of the contact lens and such water loss is primarily controlled by water diffusion through a lens from the posterior surface to the anterior surface
Implementation Method 3
a SiHy lenses worn in the eye may have dry spots and/or hydrophobic surface areas created due to air exposure, shearing forces of the eyelids, silicone migration
Data Source
AI summary
The invention is related to a hydrated silicone hydrogel contact lens having a layered structural configuration: a lower water content silicone hydrogel core (or bulk material) completely covered with a layer of a higher water content hydrogel totally or substantially free of silicone. A hydrated silicone hydrogel contact lens of the invention possesses high oxygen permeability for maintaining the corneal health and a soft, water-rich, lubricious surface for wearing comfort.