PVA-PVP Contact Lens Packaging for Long-Lasting Lubrication
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Solution Overview
Problem
Soft contact lenses often cause discomfort due to frictional forces during blinking, leading to a sensation of something in the eye, and existing surface lubrication methods using polyacrylic acid (PAA) are unstable over time and costly to maintain.
Innovation Solution
A contact lens packaging solution containing polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) forms a stable shell layer through interpenetrating polymer networks (IPN) during sterilization, enhancing lubricity and maintaining comfort over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyacrylic acid (PAA) is used to cover the lens surface, then surface lubrication effect is achieved, but the lens causes irritant problems due to sensitivity to pH changes and electrical property instability
Solution Approach 1:
The patent uses a composite material system consisting of polyacrylic acid (PAA) crosslinked with borax and further crosslinked with polyvinyl alcohol (PVA). This multi-component composite structure combines the lubrication properties of PAA with the stability of borax-PVA crosslinking, creating a surface coating that maintains lubrication effect while resisting pH changes and electrical property fluctuations that would otherwise cause instability.
Solution Approach 2:
The patent changes the chemical and physical parameters of the lens surface by introducing crosslinking agents (borax and PVA) that modify the molecular structure of the PAA coating. This crosslinking transforms the linear PAA chains into a three-dimensional network structure, altering parameters such as charge distribution, pH sensitivity, and mechanical stability, thereby maintaining lubrication while improving reliability.
2Reliability
If cationic polymer is used to neutralize PAA electrical property, then stability is improved, but manufacturing cost increases and long-term lubrication effect is lost
Solution Approach 1:
The patent introduces borax as an intermediary substance that mediates between the anionic PAA and the need for electrical stability. Instead of directly adding cationic polymers that would neutralize charges, borax acts as a crosslinking agent that forms a stable network structure, indirectly achieving electrical property stability while maintaining the anionic nature and lubrication properties of PAA.
Solution Approach 2:
The patent replaces expensive cationic polymers with a more cost-effective crosslinking system using borax and PVA. This alternative crosslinking approach achieves the desired stability at lower manufacturing cost, making the process more economically viable while maintaining the lubrication effect over extended periods.
3Ease of operation
If soft contact lens material is used, then comfort is improved compared to rigid gas-permeable lens, but frictional force during blinking causes discomfort and sensation of something in the eye
Solution Approach 1:
The patent applies a localized surface treatment to the soft contact lens by coating the lens surface with a PAA-borax-PVA crosslinked network. This local modification concentrates the lubrication properties at the lens-eyeball interface where friction occurs during blinking, while the bulk lens material retains its soft and comfortable characteristics. The surface coating specifically addresses the friction problem without compromising the overall comfort provided by the soft lens material.
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 PVA-PVP IPN shell layer provides long-lasting lubrication, reducing friction and enhancing user comfort without the stability issues associated with anionic polymers like PAA.
Implementation Method 1
forms a stable shell layer through interpenetrating polymer networks (IPN) during sterilization
Implementation Method 2
The PVA-PVP IPN shell layer provides long-lasting lubrication, reducing friction
Data Source
AI summary
The present invention provides a contact lens packaging solution, suitable for soaking a core lens body, and performing a sterilization step when the core lens body is soaked in the contact lens packaging solution. The contact lens packaging solution includes a first polymer and a second polymer. The first polymer comprises polyvinyl alcohol, and the second polymer comprises polyvinylpyrrolidone. The present invention also provides a method for manufacturing contact lenses.