Silicone Hydrogel Contact Lenses Low Modulus Oxygen Permeability

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Solution Overview

Problem

Current silicone hydrogel contact lenses face challenges in reducing elastic modulus while maintaining high oxygen permeability, as existing methods often compromise oxygen permeability or increase production costs and alter physical properties.

Innovation Solution

Incorporating a chain transfer agent in the polymerizable fluid composition with siloxane-containing macromers to reduce the elastic modulus of silicone hydrogel materials while maintaining or slightly decreasing oxygen permeability, achieving a balance between comfort and corneal health benefits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the percentage of silicon-containing macromer is lowered to decrease elastic modulus, then lens comfort is improved, but oxygen permeability decreases

Engineering Contradiction:

Improveelastic modulusVSAvoidoxygen permeability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters by introducing fluorinated monomers and adjusting the ratio of hydrophilic to hydrophobic components. This allows achieving low elastic modulus (improved comfort) while maintaining high oxygen permeability through the fluorinated groups' inherent oxygen transport properties

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite silicone hydrogel material combining siloxane-containing macromers with fluorinated monomers and hydrophilic monomers. This composite structure achieves both low modulus (from hydrophilic components) and high oxygen permeability (from fluorinated and siloxane components) simultaneously

Inventive Principle:

Principle #40Composite materials

2Strength

If customized modulus-lowering monomer is used to reduce elastic modulus, then lens comfort is improved, but production cost increases

Engineering Contradiction:

Improveelastic modulusVSAvoidproduction cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent uses commercially available, inexpensive fluorinated monomers and standard hydrophilic monomers instead of expensive customized monomers. These off-the-shelf components can be obtained from regular chemical suppliers, significantly reducing production costs while achieving the desired low elastic modulus

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Strength

If methacrylate is replaced by corresponding acrylate to lower elastic modulus, then lens comfort is improved, but glass transition temperature and hardness decrease adversely affecting lathing ability

Engineering Contradiction:

Improveelastic modulusVSAvoidglass transition temperature

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent carefully selects fluorinated monomers with appropriate molecular weights and structural parameters to achieve the desired elastic modulus reduction while maintaining glass transition temperature above freezing point. The specific parameter selection ensures lathing ability is preserved

Inventive Principle:

Principle #35Parameter changes

4Strength

If hydrophilic monomer concentration is increased to lower elastic modulus, then lens comfort is improved, but oxygen permeability decreases

Engineering Contradiction:

Improveelastic modulusVSAvoidoxygen permeability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent creates a composite formulation where fluorinated monomers provide oxygen permeability while hydrophilic monomers provide low elastic modulus. The synergistic combination allows both high oxygen permeability and low modulus to coexist, resolving the trade-off between comfort and oxygen transport

Inventive Principle:

Principle #40Composite materials

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 method effectively produces silicone hydrogel contact lenses with high oxygen permeability and low elastic modulus, ensuring patient comfort and corneal health without adverse effects on physical properties or production costs.

Implementation Method 1

the chain transfer agent is present in the polymerizable fluid composition in an amount sufficient to provide a reduced elastic modulus to the silicone hydrogel material

Methodology Applied

Scientific EffectChain transfer:

Implementation Method 2

soft contact lenses must allow oxygen to diffuse through the lens to reach the cornea, namely having a relatively high oxygen transmissibility

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS7671156B2Silicone hydrogels

Publication Date: 2010.03.02 ALCON INC

AI summary

The present invention provides silicone hydrogel materials having relatively high oxygen permeability and a relatively low modulus. The relatively-low modulus is achieved by adding a chain transfer agent into a polymerizable fluid composition in an amount sufficient to provide to the resultant silicone hydrogel material with a reduced modulus. In addition, the invention provides silicone hydrogel contact lenses comprising a silicone hydrogel material of the invention, a method for making a silicone hydrogel material of the invention, and a method for making a silicone hydrogel contact lens of the invention.