Water Gradient Contact Lens PAE Intermediary Layer
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Solution Overview
Problem
Existing water gradient silicone hydrogel contact lenses are not compatible with all multipurpose lens care solutions due to high uptake of polycationic antimicrobials, leading to undesirable clinical symptoms and limited suitability for weekly or monthly disposable use.
Innovation Solution
Development of contact lenses with a polyquaternium-1 uptake of about 0.4 micrograms/lens or less, combined with a long-lasting surface hydrophilicity and wettability characterized by a water-break-up time of at least 10 seconds after digital rubbing treatment, ensuring compatibility with multipurpose lens care solutions and resistance to digital rubbings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polyanionic anchoring layer is applied to provide water gradient structure and lubricity, then wearing comfort is improved, but uptake of polycationic antimicrobials increases causing incompatibility with multipurpose lens care solutions
Solution Approach 1:
A polyamidoamine-epichlorohydrin (PAE) intermediate layer is introduced between the polyanionic anchoring layer and the hydrogel coating. This PAE layer acts as a mediator that reduces the electrostatic attraction between the negatively charged anchoring layer and positively charged polycationic antimicrobials, thereby reducing antimicrobial uptake while preserving the water gradient structure and lubricity benefits.
Solution Approach 2:
The patent modifies the chemical parameters of the anchoring layer by incorporating PAE with specific molecular weight and composition ratios. By adjusting the PAE to wetting agent ratio and reaction conditions, the surface charge density and hydrophilicity are optimized to reduce polycationic antimicrobial uptake while maintaining lubricity and water content gradient.
2Ease of operation
If hydrogel coating is made thick and water-rich to provide lubricity, then wearing comfort is improved, but resistance to digital rubbing damages decreases
Solution Approach 1:
The patent creates a composite structure combining the polyanionic anchoring layer, PAE intermediate layer, and hydrogel coating. This multi-layer composite provides both the water-rich lubricious surface needed for comfort and the structural integrity to resist digital rubbing damages through the reinforcing anchoring and intermediate layers.
Solution Approach 2:
The anchoring layer and PAE intermediate layer are applied to the contact lens before the hydrogel coating is formed. This preliminary application of structural layers creates a durable foundation that prevents subsequent damage to the hydrogel coating during digital rubbing and lens handling.
3Reliability
If water-soluble highly-branched hydrophilic polymeric material is covalently attached to provide water gradient structure, then surface hydrophilicity is improved, but susceptibility to surface defects increases
Solution Approach 1:
The PAE intermediate layer serves as a protective intermediary between the anchoring layer and the hydrogel coating. This intermediate layer reduces mechanical stress and prevents surface defects in the hydrogel coating while maintaining the water gradient structure and hydrophilicity through proper selection of PAE composition and thickness.
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 contact lenses provide superior wearing comfort, are compatible with multipurpose lens care solutions, and can withstand harsh lens care handling conditions, making them suitable for weekly or monthly disposable use.
Implementation Method 1
water gradient structural configuration, an increase from 33% to over 80% water content from core to surface
Implementation Method 2
having a relative high resistance to uptakes of polycationic antimicrobials
Data Source
AI summary
The invention is related to contact lenses that not only comprise the much desired water gradient structural configurations, but also have a minimized uptakes of polycationic antimicrobials and a long-lasting surface hydrophilicity and wettability even after going through a 30-days lens care regime. Because of the water gradient structural configuration and a relatively-thick, extremely-soft and water-rich hydrogel surface layer, a contact lens of the invention can provide superior wearing comfort. Further, a contact lens of the invention is compatible with multipurpose lens care solutions present in the market and can endure the harsh lens care handling conditions (e.g., digital rubbings, accidental inversion of contact lenses, etc.) encountered in a daily lens care regime. As such, they are suitable to be used as weekly- or monthly-disposable water gradient contact lenses.