Contact Lens Extraction Using Buffered pH Solutions
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Solution Overview
Problem
Contact lens manufacturing processes face challenges in effectively removing undesirable extractable materials like unreacted monomers while minimizing solvent usage and environmental impact, and in avoiding damage to lenses from elevated temperatures during processing.
Innovation Solution
A method involving stepwise processing of contact lenses with extraction media of varying water and organic solvent concentrations, including the use of non-aqueous solvents like ethanol, to efficiently remove extractable materials and hydrate lenses, reducing stress and environmental waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large amounts of solvents are used for extracting monomers and extractable materials from contact lenses, then extraction effectiveness is improved, but manufacturing cost increases and environmental harm worsens
Solution Approach 1:
The patent changes the chemical parameters of the extraction medium by using buffered aqueous solutions with specific pH ranges (pH 7-9 for first extraction, pH 5-7 for second extraction) instead of traditional organic solvents. This parameter change maintains extraction effectiveness while dramatically reducing environmental harm and manufacturing cost.
Solution Approach 2:
The patent implements a two-stage extraction process where the first extraction medium (buffered solution at pH 7-9) is discarded after use, and a second extraction medium (buffered solution at pH 5-7) is used for further extraction. This staged approach optimizes extractant recovery while minimizing overall solvent usage and environmental impact.
2Productivity
If elevated temperatures are used during sterilizing and processing, then processing efficiency is improved, but contact lens damage increases
Solution Approach 1:
The patent changes the temperature parameter from conventional high-temperature sterilization to low-temperature processing (maintaining temperatures below 40°C during extraction and hydration). This parameter change prevents lens damage from discolouring and weakening while maintaining processing efficiency through optimized chemical extraction conditions.
Solution Approach 2:
The patent replaces thermal sterilization mechanisms with chemical extraction mechanisms using buffered solutions. Instead of relying on high temperature for sterilization and processing, the system uses chemically buffered aqueous environments to achieve both extraction and sterilization functions at lower temperatures, thereby preventing lens damage.
3Manufacturing precision
If conventional extraction methods are used, then extractable materials are removed, but lens dehydration and stress occur
Solution Approach 1:
The patent changes the pH parameter of the extraction medium through buffered solutions, maintaining physiological pH ranges (pH 7-9 then pH 5-7) that are compatible with lens hydration. This prevents the lens dehydration and stress that occur with conventional non-buffered solvents while still effectively removing extractable materials.
Solution Approach 2:
The patent introduces buffered aqueous solutions as intermediary extraction media that mediate between the need for effective monomer removal and the need to maintain lens hydration stability. The buffers act as intermediaries that create a chemically stable environment preventing lens stress while enabling effective extraction.
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
This approach effectively reduces extractable materials by up to 90%, minimizes solvent usage, and ensures lenses are safe and comfortable for extended wear, while also reducing environmental impact and operational costs.
Implementation Method 1
contacting the contact lens with an extraction medium comprising less than 5% by weight of water and an organic component effective to solubilize extractable material contained in the contact lens
Implementation Method 2
a swellable, polymeric contact lens is a polymeric contact lens which is capable of becoming swelled with a medium, such as a liquid medium
Data Source
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AI summary
The present contact lens treating systems and methods effectively remove extractable materials from contact lenses, for example, newly formed contact lenses, so that the lenses can be safely and conveniently worn, for example, for extended periods of time. Such treatment methods and the present extraction medium reprocessing methods allow lens treatment while reducing extraction medium losses. The present methods can also be useful for manufacturing a heat stabilized contact lens, for example, a water swelled contact lens including a Vitamin E component which is insoluble in the lens in a hydrated state.