Silicone Hydrogel Contact Lens Shape Stability
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Solution Overview
Problem
Silicone hydrogel soft contact lenses experience dimensional instability and shape changes during long-term storage, leading to issues with wearing comfort and optical characteristics due to challenges in maintaining precise dimensions and shape stability under hermetically sealed conditions.
Innovation Solution
A manufacturing method involving high pressure steam sterilization of silicone hydrogel contact lenses immersed in a storage solution containing phosphoric acid, which stabilizes the lens shape and dimensions, preventing changes over time, with optimal phosphoric acid concentration between 0.01 to 1.0 weight % and pH range of 7.2 to 8, ensuring shape stability and maintaining lens strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If silicone hydrogel contact lenses are stored in a hermetically sealed package for long-term preservation, then the lenses can be maintained in a stable state for shipping and storage, but the lenses undergo shape changes and dimensional instability over time
Solution Approach 1:
The patent changes the chemical composition parameters of the storage solution by adding phosphoric acid at a specific concentration (0.01-1.0 wt%). This parameter change in the storage environment prevents the dimensional instability and shape changes that occur in conventional storage solutions, thereby maintaining lens shape stability throughout the storage period.
Solution Approach 2:
The phosphoric acid in the storage solution acts as an intermediary substance that mediates between the contact lens material and the storage environment. It prevents the harmful shape changes by creating a stabilizing chemical environment during high-pressure steam sterilization and long-term storage, without directly altering the lens structure.
2Reliability
If conventional storage solutions are used for hermetically sealed contact lens packages, then the lenses can be preserved, but dimensional precision and shape stability cannot be sufficiently ensured
Solution Approach 1:
The patent modifies the chemical parameters of the storage solution by incorporating phosphoric acid at a controlled concentration (0.01-1.0 wt%). This parameter change ensures both reliable preservation and maintenance of dimensional precision, as the phosphoric acid prevents the lens material from undergoing shape changes during storage while maintaining sterility.
3Reliability
If high pressure steam sterilization is performed on silicone hydrogel contact lenses, then the lenses achieve sterile preservation, but shape changes and diameter increase occur after sterilization
Solution Approach 1:
The phosphoric acid in the storage solution serves as an intermediary that protects the contact lens dimensions during high-pressure steam sterilization. It creates a stabilizing chemical environment that prevents the diameter increase and shape changes that would otherwise occur during the sterilization process and subsequent storage.
Solution Approach 2:
By changing the chemical composition of the storage solution to include phosphoric acid, the patent alters the physical-chemical parameters during sterilization. This parameter change prevents the harmful dimensional changes while maintaining the sterilization effectiveness, as the phosphoric acid stabilizes the lens material structure during the high-temperature steam exposure.
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 effectively maintains the initial shape and dimensions of silicone hydrogel contact lenses for extended periods, adhering to product standards with minimal deviation, enhancing wearing comfort and optical performance by suppressing shape and dimension changes, even after several months or years of storage.
Implementation Method 1
performing high pressure steam sterilization processing with the silicone hydrogel contact lenses in a state immersed in a storage solution containing a phosphoric acid, the shape stability (dimensional stability) of the silicone hydrogel contact lenses becomes better after that
Implementation Method 2
performing high pressure steam sterilization processing with the silicone hydrogel contact lenses in a state immersed in a storage solution containing a phosphoric acid
Data Source
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AI summary
Provided is a novel contact lens package containing a silicone hydrogel soft contact lens, which can be offered to the market in a hermetically sealed preserved state with excellent shape stability (dimensional stability). Also provided is a manufacturing method of the same. The novel contact lens package is manufactured by using a silicone hydrogel contact lens as a soft contact lens (12), sealing both a storage solution (14) so as to contain a phosphoric acid and the silicone hydrogel contact lens (12) in a housing area (22) of a contact lens package (10), and then performing high pressure steam sterilization processing.