Crosslinked Hydrophilic Coating for Silicone Hydrogel Lenses
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicone hydrogel contact lenses face challenges with hydrophobic surfaces that lead to ocular irritation due to adsorption of lipids and proteins, and the use of positively charged preservatives like PHMB, which cause eye irritation by concentrating on the lens and releasing when in contact with the eye, necessitating a cost-effective and time-efficient method for reducing preservative uptake and enhancing hydrophilicity and lubricity.
Innovation Solution
A method involving a crosslinked hydrophilic coating on silicone hydrogel contact lenses using a water-soluble, thermally-crosslinkable polymeric material with azetidinium groups, applied through a packaging solution that includes a buffering agent and a polyazetidinium groups-containing component, reducing the concentration of amino and carboxyl groups to decrease positively charged preservative uptake while improving hydrophilicity and lubricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a hydrophobic silicone hydrogel contact lens is used, then oxygen permeability is improved, but surface wettability deteriorates causing lipid and protein adsorption
Solution Approach 1:
The patent applies local quality by modifying only the surface region of the contact lens with hydrophilic functional groups (amino and carboxyl groups) while maintaining the bulk silicone hydrogel material's high oxygen permeability properties. This creates a gradient where the surface has different properties (hydrophilic) than the bulk material (hydrophobic, high oxygen permeability), resolving the contradiction between oxygen permeability and surface wettability.
2Object-affected harmful factors
If amino groups and carboxyl groups are introduced on the lens surface to improve hydrophilicity, then surface wettability is improved, but positively charged preservative uptake increases
Solution Approach 1:
The patent applies parameter changes by optimizing the density and ratio of amino groups to carboxyl groups on the lens surface. By carefully controlling these parameters during the surface modification process, the lens achieves sufficient hydrophilicity for comfort while limiting the total positive charge available for binding to positively charged preservatives like PHMB, thus reducing preservative uptake.
3Object-affected harmful factors
If known methods for attaching hydrophilic polymers are used, then surface hydrophilicity is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent merges the surface modification step with the existing contact lens manufacturing process. The hydrophilic functional groups are introduced during the lens fabrication process itself rather than as a separate post-processing step, combining multiple functions into a single integrated process and reducing manufacturing complexity and time.
4Object-affected harmful factors
If known methods for attaching hydrophilic polymers are used, then surface hydrophilicity is improved, but production time increases
Solution Approach 1:
The patent applies preliminary action by incorporating the introduction of hydrophilic functional groups into the lens manufacturing process before the lens is completed and packaged. This preliminary modification eliminates the need for separate hydrophilization treatment steps after manufacturing, thereby reducing total production time and improving productivity.
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 reduces positively charged preservative uptake by at least 20% while maintaining surface hydrophilicity and lubricity, enhancing the comfort and safety of the contact lens wear by minimizing eye irritation.
Implementation Method 1
heating the silicone hydrogel contact lens immersed in an in-packing-coating packaging solution comprising the hydrophilic polymeric material... to and at a temperature from about 40°C to about 140°C... for a period of time sufficient to covalently attach the hydrophilic polymeric material onto the surface
Implementation Method 2
covalently attach the hydrophilic polymeric material onto the surface of the silicone hydrogel contact lens through second covalent linkages each formed between one azetidinium group of the hydrophilic polymeric material and one of the reactive functional groups on and/or near the surface of the contact lens
Implementation Method 3
When contact lens care products containing compounds bearing positive charges are used with the contact lenses, an ionic interaction can take place between the contact lenses and those components
Implementation Method 4
With water absorption, the lenses also may take up chemicals dissolved in the water
Data Source
AI summary
The present invention generally relates to a cost-effective and time-efficient method for applying a crosslinked hydrophilic coating onto a silicone hydrogel contact lens to reduce its positively charged preservatives such as PHMB uptake and to improve its hydrophilicity and lubricity.