Silicone Hydrogel Contact Lens Coating Durability

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Solution Overview

Problem

Current methods for modifying silicone hydrogel contact lenses to enhance hydrophilicity and lubricity are either costly, inefficient, or result in coatings that are susceptible to deposition and accumulation of positively charged antimicrobials, leading to undesirable clinical symptoms.

Innovation Solution

A method involving a preformed silicone hydrogel contact lens is treated with a plasma to form a prime plasma layer, followed by a reactive polymer layer, and then heated in an aqueous solution with a thermally-crosslinkable hydrophilic polymeric material to create a durable, lubricious non-silicone hydrogel coating with minimized susceptibility to antimicrobial deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If plasma treatment is used to modify the hydrophilicity of silicone hydrogel contact lenses, then the hydrophilicity and durability are improved, but the manufacturing cost and capital investment increase

Engineering Contradiction:

Improvecoating durabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent introduces a plasma treatment step as an intermediary process between lens fabrication and final coating application. The plasma treatment modifies the surface energy and chemistry of the silicone hydrogel lens, creating a more receptive substrate for subsequent polymer coating. This intermediary treatment enables better adhesion and durability of the coating without requiring expensive plasma treatment equipment to be the final coating mechanism itself, thereby reducing capital investment while maintaining reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If LbL polyionic material deposition is used to render silicone hydrogel material wettable, then the manufacturing cost is reduced, but the coating durability decreases and susceptibility to antimicrobial deposition increases

Engineering Contradiction:

Improvemanufacturing costVSAvoidcoating durability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent employs a composite coating structure consisting of multiple polymer layers with different functional properties. The coating comprises a hydrophilic polymer matrix combined with crosslinking agents and surfactants, creating a multi-component composite material. This composite approach provides both durability through crosslinked network formation and resistance to antimicrobial deposition through hydrophilic surfaces, while avoiding the high costs of plasma treatment equipment.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes crosslinking chemistry to fundamentally change the physical and chemical parameters of the coating. By introducing crosslinks between polymer chains, the coating transitions from a simple adsorbed layer to a durable, integrated surface modification. This parameter change in the coating structure (from linear to crosslinked network) significantly improves durability and resistance to antimicrobial accumulation while maintaining the cost-effectiveness of polymer deposition techniques.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If LbL coatings are applied to silicone hydrogel contact lenses, then the hydrophilicity is improved, but the surface charge density increases leading to antimicrobial accumulation

Engineering Contradiction:

Improvesurface hydrophilicityVSAvoidantimicrobial deposition

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality modification by creating a coating with spatially distributed functional groups. The hydrophilic polymer coating provides localized hydrophilic regions that repel antimicrobial substances, while crosslinking points are distributed throughout the coating matrix. This local quality approach ensures that hydrophilicity is maintained at the surface interface with tears, preventing antimicrobial adhesion without requiring uniform high charge density throughout the entire coating structure.

Inventive Principle:

Principle #3Local quality

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 produces a coating with improved durability and reduced susceptibility to antimicrobial deposition, maintaining high hydrophilicity and lubricity, thus enhancing the biocompatibility and comfort of silicone hydrogel contact lenses.

Implementation Method 1

treating the preformed silicone hydrogel contact lens with a plasma to form a prime plasma layer thereon

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

heating the silicone hydrogel contact lens with the base coating thereon in an aqueous solution with a thermally-crosslinkable hydrophilic polymeric material to create a durable, lubricious non-silicone hydrogel coating

Methodology Applied

Scientific EffectThermal crosslinking:

Data Source

PatentEP3344447B1Method for producing contact lenses with durable lubricious coatings thereon

Publication Date: 2019.12.11 ALCON INC

AI summary

The invention is related to a method for producing silicone hydrogel contact lenses with a stable lubricious hydrogel coating thereon. A method of the invention comprises forming a plasma-reactive hydrophilic polymer hybrid base coating having reactive functional groups on a silicone hydrogel contact lens and heating the silicone hydrogel contact lens with the hybrid base coating in an aqueous solution of a water-soluble and thermally crosslinkable hydrophilic polymeric material to form a stable lubricious hydrogel coating thereon.