Toric Ophthalmic Lens Dual-Surface Astigmatism Correction
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Solution Overview
Problem
Conventional ophthalmic lenses for correcting astigmatism only utilize one optical surface as a toric surface, failing to properly control cylindrical refractivity across the cornea, leading to incomplete astigmatism correction and limited visual function improvement.
Innovation Solution
A toric ophthalmic lens with varying refractivity differences between perpendicular directions on its surface, allowing for separate control of astigmatism correction at the center and periphery, and distinct management of spherical aberrations in different directions to address astigmatism across the cornea.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If only one optical surface is used as a toric surface in conventional ophthalmic lenses, then the lens structure is simple, but the cylindrical refractivity cannot be properly controlled across the cornea, resulting in incomplete astigmatism correction
Solution Approach 1:
The lens is divided into two optical surfaces, each with distinct functions: the first optical surface (toric surface) corrects astigmatism while the second optical surface corrects spherical aberration. This segmentation allows independent optimization of each surface's refractive properties to achieve comprehensive correction
Solution Approach 2:
Each optical surface is designed with specific local refractive characteristics tailored to its function. The toric surface has varying curvature in different meridians to address astigmatism, while the other surface has specific curvature profiles to address spherical aberration, ensuring each region of the lens provides the appropriate correction
2Reliability
If conventional toric lenses are used, then the lens design is straightforward, but astigmatism components cannot be properly removed over the whole cornea, limiting visual function improvement
Solution Approach 1:
The correction function is segmented between two surfaces: the toric surface handles astigmatism correction while the other surface handles spherical aberration, allowing comprehensive correction across the entire cornea including both central and peripheral regions
Solution Approach 2:
The refractive indices and curvature radii of both optical surfaces are specifically designed and optimized to achieve proper correction. The toric surface has different curvature radii in different meridians (R1 in first meridian, R2 in second meridian), while the other surface has specific curvature profiles, creating the necessary parameter variations for comprehensive correction
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 lens effectively corrects astigmatism across the entire cornea, providing improved visual acuity and reducing blurring, as demonstrated by simulation and measurement results, compared to conventional toric lenses.
Implementation Method 1
Due to a toric surface, the refractivity of a lens differs between directions orthogonal to each other which are set on the toric surface. Astigmatism can be corrected by making use of the difference in refractivity.
Data Source
AI summary
A tonic ophthalmic lens is described in which refractivity of the lens differs between a first direction on a plane perpendicular to an optical axis of the lens and a second direction which differs from the first direction on the plane. In addition, refractivity difference which is the difference between the refractivity in the first direction and the refractivity in the second direction varies depending on a position of the lens in a radial direction.