Buffered Packaging Solution for Silicone Hydrogel Contact Lenses
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Solution Overview
Problem
Current contact lens packaging solutions at neutral pH can facilitate the growth of harmful microorganisms and are not compatible with the hydrolytic instability of silicone hydrogel lenses, especially when exposed to acidic monomers, which can degrade the lenses' properties over time.
Innovation Solution
A low pH buffered packaging solution with a pH range of 4.5 to 6.5, comprising a borate compound and a phosphate compound, along with a non-ionic tonicity agent, is used to stabilize silicone hydrogel contact lenses and prevent microbial growth, maintaining the lenses' mechanical properties even after sterilization cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If neutral pH buffered saline is used as packaging solution, then the solution is gentle to the eye, but it facilitates the growth of harmful microorganisms
Solution Approach 1:
The patent changes the pH parameter of the packaging solution from neutral (pH 7) to acidic (pH 4.5-6.5) to inhibit microbial growth. This parameter change resolves the contradiction by creating an environment hostile to microorganisms while maintaining compatibility with silicone hydrogel contact lenses through controlled acidification using buffered solutions.
2Object-affected harmful factors
If low pH packaging solution is used, then microbial growth is inhibited, but it causes hydrolysis of silicone groups in contact lenses
Solution Approach 1:
The patent introduces buffered packaging solutions (containing buffer systems) as an intermediary between the acidic environment needed for microbial inhibition and the silicone hydrogel lens material. The buffer system mediates the pH environment to prevent both microbial growth and hydrolytic degradation of the lens, resolving the contradiction by creating a controlled chemical environment.
3Reliability
If acidic monomers are present in silicone hydrogel lenses, then lens properties are enhanced, but they become more susceptible to hydrolysis in acidic packaging solutions
Solution Approach 1:
The patent carefully controls and adjusts the pH parameter of the packaging solution to a specific range (pH 4.5-6.5) that is sufficiently acidic to inhibit microbial growth but not so acidic as to cause excessive hydrolysis of acidic monomers in the lens. This precise parameter control allows the lens to maintain its functional properties while resisting degradation.
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 solution effectively inhibits microbial growth and maintains the mechanical stability of silicone hydrogel contact lenses, ensuring they remain intact and functional even after multiple sterilization cycles, while being safe for direct application to the eye.
Implementation Method 1
A low pH buffered packaging solution with a pH range of 4.5 to 6.5, comprising a borate compound and a phosphate compound
Implementation Method 2
the modulus of PureVision contact lenses can increase from 155 psi to 576 psi when heated at 95° C. for one week due to the hydrolysis of the tris[trimethylsiloxy]silane groups in the presence of small amounts of the acidic comonomer Vinal
Data Source
AI summary
The present invention relates to a sealed ophthalmic product or kit, comprising a package comprising a sealed compartment comprising at least one sterile silicone hydrogel contact lens and a buffered packaging solution having a low pH.