Tear Substitute Composition for Surfactant-Free Corneal Wetting
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Solution Overview
Problem
Existing tear substitutes do not effectively wet the corneal surface, particularly in areas with damaged or absent mucin layers, and formulations using surfactants to enhance wettability pose toxic risks to the corneal epithelium.
Innovation Solution
A tear substitute composition comprising hyaluronic acid, mineral salts, potassium citrate, glycerol, and polyvinyl alcohol (PVA) in specific concentrations, particularly PVA 0.25%, to improve wettability on hydrophobic surfaces mimicking the cornea, without using surfactants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surfactants are used to enhance wettability, then wettability is improved, but toxic effects on corneal epithelium worsen
Solution Approach 1:
The patent changes the chemical composition parameters by using polyvinyl alcohol (PVA) at optimized concentrations (0.1-0.3%) instead of conventional surfactants. This parameter change achieves improved wettability (contact angle reduction) while avoiding the toxic effects associated with surfactant use on corneal epithelium.
Solution Approach 2:
PVA acts as an intermediary substance that mediates between the hydrophobic corneal surface and the aqueous tear substitute formulation. It reduces surface tension and improves wettability without the harmful effects of direct surfactant contact with sensitive corneal tissues.
2Reliability
If PVA concentration is increased to improve wettability, then wettability is enhanced, but viscosity stability worsens
Solution Approach 1:
The patent optimizes the PVA concentration parameter to a specific range (0.1-0.3%, preferably 0.25%) where wettability is maximized while viscosity stability is maintained. This precise parameter optimization balances the competing requirements of enhanced wetting and rheological stability.
Solution Approach 2:
Rather than using high concentrations of PVA that would guarantee wettability improvement, the patent applies partial action by using low concentrations (0.1-0.3%) that are sufficient to achieve the desired wettability enhancement while avoiding the negative impact on viscosity stability.
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 composition significantly enhances wettability on hydrophobic surfaces, maintaining rheological stability and pH stability, and reduces toxic effects, demonstrating improved corneal surface wetting comparable to the natural cornea.
Implementation Method 1
US4883658 describes a formulation comprising partially hydrolyzed PVA and fully hydrolyzed PVA, wherein said formulation is able to lead to a significant lowering of the surface tension of the aqueous solution and to a significant increase in the wettability of the hydrophobic surfaces.
Implementation Method 2
The present invention relates to a composition comprising PVA in amounts between 0.1 and 0.3% by weight, preferably 0.25%, characterized by an optimal wettability for use as a tear substitute.
Implementation Method 3
WO2008011836 describes the synergistic effect on the viscosity obtained by combining hyaluronic acid and PVA, wherein the used percentages of PVA are between 0.25% and 4%.
Data Source
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Figure 3~4B
AI summary
The present invention relates to a composition comprising polyvinyl alcohol (PVA) in amounts between 0.1 and 0.3% by weight, preferably 0.25%, characterized by an optimal wettability for use as a tear substitute.