Polysiloxane Soft Lens with Acid-Base Coating for Corneal Adhesion
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Solution Overview
Problem
Conventional low water content soft contact lenses suffer from adhesion to the cornea and high risk of bacterial growth due to their hydrophilic nature, leading to discomfort and potential eye dryness issues.
Innovation Solution
A low water content soft lens with a polysiloxane compound having multiple polymerizable functional groups and a fluoroalkyl group, coated with layers of acidic and basic polymers to reduce adhesion and enhance oxygen permeability, comfort, and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hydrogel material with high water content is used to improve comfort and wettability, then the lens feels more comfortable and maintains better wettability, but the risk of bacterial growth increases and the lens becomes less mechanically stable
Solution Approach 1:
The patent applies parameter changes by precisely controlling the water content of the hydrogel material to fall within the range of 30-80%, optimizing the balance between comfort and safety. This specific parameter range ensures sufficient wettability and comfort while limiting the water available for bacterial growth and maintaining mechanical stability.
Solution Approach 2:
The patent uses composite materials by combining hydrogel material with specific physical and chemical properties (controlled water content, oxygen permeability) to create a lens that integrates both comfort and safety functions. The composite structure allows the lens to maintain mechanical stability while providing the wettability benefits of hydrogel materials.
2Reliability
If a silicone rubber lens is used to achieve high oxygen permeability and low water content, then oxygen permeability improves and water content decreases, but the lens surface becomes hydrophobic causing adhesion to the cornea and peeling of hydrophilized layers
Solution Approach 1:
The patent applies local quality by creating a lens with non-uniform properties: the bulk material maintains low water content and high oxygen permeability characteristics of silicone rubber, while the surface is modified to provide appropriate wettability. This local differentiation allows the lens to simultaneously achieve high oxygen permeability in the bulk and reduced adhesion at the surface.
Solution Approach 2:
The patent uses parameter changes by modifying the surface properties of the silicone rubber lens through controlled water content and surface treatment, transforming the surface from highly hydrophobic to having moderate wettability. This parameter adjustment reduces the adhesion force between the lens and cornea while maintaining the high oxygen permeability of the bulk material.
3Ease of operation
If the lens surface is made highly hydrophilic to reduce adhesion, then adhesion to the cornea decreases, but the lens loses mechanical strength and folding resistance
Solution Approach 1:
The patent applies local quality by concentrating the hydrophilic modification only at the lens surface rather than throughout the entire lens structure. This allows the surface to have reduced adhesion properties while the bulk material maintains its mechanical strength and folding resistance, as the structural integrity is determined by the bulk material properties.
Solution Approach 2:
The patent uses partial action by applying hydrophilic modification to only the surface layer of the lens rather than the entire lens. This partial modification is sufficient to reduce adhesion to the cornea while leaving the bulk material unchanged, thereby preserving the mechanical strength and folding resistance required for lens durability.
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 significantly reduces corneal adhesion, minimizes bacterial growth risk, and provides improved comfort and mechanical properties while maintaining low water content, ensuring excellent wettability and lubricity.
Implementation Method 1
a method of alternately forming layers made of two polymer materials, each having an opposite electric charge, in a layer by layer fashion by coating is called an LbL method, and it is considered that each layer of the material is noncovalently bonded to the other layer made of a different material
Implementation Method 2
a polymer obtained by polymerizing a difunctional organosiloxane macromer alone, or a polymer obtained by copolymerizing a difunctional organosiloxane macromer with the other monomers
Data Source
Figure 1
AI summary
Disclosed is a low water content soft lens for eye, which includes a layer made of an acidic polymer and a basic polymer on at least a part of a surface of a base material containing a polysiloxane compound. The present invention provides a low water content soft lens for eye, wherein a phenomenon of adhesion of the lens to the cornea during wear, which has hitherto been regarded as a problem in a conventional low water content soft lens for eye, has been remarkably reduced or avoided.