Silicone Hydrogel Contact Lenses with Polyamide Wetting Agents
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Solution Overview
Problem
Silicone hydrogel contact lenses with high oxygen permeability often cause discomfort and ocular deposits due to their hydrophobic character, leading to reduced visual acuity, especially during extended wear, as they interact with the eye's proteins, lipids, and mucin, and existing methods struggle to incorporate high concentrations of internal wetting agents while maintaining acceptable physical and biological properties.
Innovation Solution
The development of silicone hydrogels formed from a reactive mixture comprising hydroxyl-substituted silicone components, at least one hydrophilic monomer, and greater than 15 wt% of polyamide, which acts as an internal wetting agent, improving wettability and biocompatibility without the need for surface treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone hydrogel contact lenses are made with high oxygen permeability, then oxygen transmission to the eye is improved, but the hydrophobic character causes discomfort and ocular deposits
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating polyamides with specific molecular weights (combining low MW polyamides for wettability with high MW polyamides for structural integrity) and adjusting their concentrations (e.g., 5-20 wt% low MW, 5-30 wt% high MW) to achieve the desired balance between hydrophobicity and hydrophilicity while maintaining oxygen permeability
Solution Approach 2:
The patent creates a composite silicone hydrogel material combining multiple components: silicone components for oxygen permeability, polyamides for hydrophilicity and wettability, and crosslinking agents for mechanical strength. This composite structure allows simultaneous achievement of high oxygen transmission and reduced ocular deposits through the hydrophilic polyamide domains
2Object-affected harmful factors
If internal wetting agents are incorporated to increase water content, then wettability is improved, but physical and mechanical properties deteriorate at high concentrations
Solution Approach 1:
The patent optimizes the molecular weight parameters of polyamides used as internal wetting agents, combining low molecular weight polyamides (for enhanced wettability) with high molecular weight polyamides (for mechanical strength). This parameter optimization allows achieving good wettability without sacrificing mechanical integrity, as the high MW polyamides provide structural support while low MW polyamides enhance surface properties
Solution Approach 2:
The patent applies local quality by using low molecular weight polyamides primarily at the surface and interface regions to enhance wettability and comfort, while high molecular weight polyamides are distributed throughout the bulk material to maintain mechanical strength and structural integrity. This spatial differentiation of polyamide functions resolves the contradiction between surface wettability and bulk mechanical properties
3Object-affected harmful factors
If polyamides are added to improve biocompatibility, then comfort is enhanced, but the complexity of formulation increases
Solution Approach 1:
The patent applies universality by selecting polyamides that simultaneously perform multiple functions: they act as internal wetting agents to improve surface wettability, provide hydrophilic domains for comfort, enhance biocompatibility by reducing protein and lipid adsorption, and contribute to the mechanical strength through their polymer network. This multi-functionality reduces formulation complexity compared to using separate additives for each function
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 resulting silicone hydrogels achieve a balance of physical, mechanical, and biological properties, enhancing comfort and reducing ocular deposits by improving wettability and maintaining high oxygen permeability, thus addressing the limitations of existing silicone hydrogel contact lenses.
Implementation Method 1
the hydrophobic character of the surfaces of lenses and the interaction of those surfaces with the protein, lipids and mucin and the hydrophilic surface of the eye
Implementation Method 2
Incorporation of internal wetting agents also affects the surface lubricity of the silicone hydrogel depending on morphology and surface roughness
Implementation Method 3
Silicone hydrogel are water-swollen polymer networks that have high oxygen permeability
Implementation Method 4
One way to increase the water content in a silicone hydrogel is to incorporate an internal wetting agent, such as a high molecular weight polymer, which creates more hydrophilic domains that retain more water
Implementation Method 5
Silicone hydrogel are water-swollen polymer networks that have high oxygen permeability
Data Source
AI summary
Described are silicone hydrogels with high levels of polyamides exhibiting an excellent balance of physical, mechanical, and biological properties. The silicone hydrogels are formed from a reactive monomer mixture comprising: a hydroxylalkyl (meth)acrylate monomer; hydroxyl-containing silicone components; and a polyamide, wherein the polyamide is present in an amount greater than 15 weight percent, based on the total weight of reactive components in the reactive monomer mixture.