Embedded Hydrogel Contact Lenses With Covalently Linked Inserts
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Solution Overview
Problem
Hydrogel contact lenses with embedded rigid inserts are prone to delamination due to significant differences in mechanical properties and water-swelling between the insert material and the silicone hydrogel lens material, leading to lens distortion during hydration and handling.
Innovation Solution
A method involving the use of a free-radical photoinitiator with ethylenically-unsaturated groups to create covalent linkages between the insert and bulk hydrogel material through thermal curing and UV/visible light irradiation, ensuring the insert is embedded and covalently linked during the lens-forming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid inserts are embedded in silicone hydrogel contact lenses, then vision correction and corneal health benefits are improved, but lens delamination and distortion occur during hydration due to mechanical property differences
Solution Approach 1:
The insert is embedded in the lens precursor material before the lens is fully formed and hydrated. This preliminary embedding allows the insert to be incorporated into the lens matrix before significant swelling occurs, preventing delamination and distortion that would occur if inserts were added after lens formation.
Solution Approach 2:
The patent changes the physical state and mechanical properties of the lens material during the embedding process. By embedding the insert in the uncured or partially cured lens precursor (which has different mechanical properties than the final hydrated lens), the insert becomes integrated into the lens structure before the material undergoes its phase transition to the final hydrated state, thereby maintaining structural integrity.
2Productivity
If conventional casting processes are used for mass production, then productivity is improved, but manufacturing precision and control over insert positioning are worsened
Solution Approach 1:
The patent merges the insert placement step with the lens casting step into a single integrated process. The insert is positioned on the mold, and the lens precursor material is cast directly over it, combining what would traditionally be separate operations. This integration maintains the efficiency of conventional casting while achieving precise insert positioning.
Solution Approach 2:
The lens precursor material itself serves the dual function of both embedding medium and final lens material. As the precursor cures and hydrates, it automatically secures the insert in place and transforms into the final lens structure, eliminating the need for separate securing or positioning operations.
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 enhances the resistance to delamination, allowing for mass production of embedded hydrogel contact lenses with improved structural integrity and reduced lens distortion.
Implementation Method 1
a first free-radical photoinitiator that comprises an ethyleneically-unsaturated group and a photoinitiator-moiety capable of generating free radicals upon irradiation by an UV and/or visible light
Implementation Method 2
a thermal free-radical initiator
Data Source
AI summary
A method for producing embedded hydrogel contact lenses comprises at least the following steps: obtaining an insert made of a crosslinked polymeric material comprising repeating units of a free-radical photoinitiator; placing the insert in a female lens mold half; dosing an amount of a lens-forming composition to immerse the insert in the female lens mold half; closing tightly a male lens mold half onto the top of the female lens mold half halves to form a molding assembly; actinically curing both the lens-forming composition in the molding assembly to form an embedded hydrogel lens precursor which comprises a bulk hydrogel material formed the lens-forming composition and the insert that is embedded therein and covalently linked to the bulk hydrogel material.