Intraocular Lens Coma Correction via Aspheric Shape Factors
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Solution Overview
Problem
Current intraocular lenses do not effectively correct for the coma of the cornea, which can degrade vision when the natural lens is replaced, leading to significant optical aberrations and reduced visual acuity.
Innovation Solution
A method for specifying the anterior and posterior surfaces of an intraocular lens by determining the optical power and shape factor, which minimizes coma by adjusting the radii and adding aspheric terms to offset the corneal coma, thereby improving the optical system's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional intraocular lens is used to replace the natural lens, then the cataract is treated and vision is restored, but the corneal coma is not corrected leading to degraded vision quality and reduced visual acuity
Solution Approach 1:
The intraocular lens is designed with specific optical characteristics (aspheric surfaces, optimized curvature radii, and refractive index distribution) that generate an optical effect opposite to the corneal coma. The lens introduces negative coma to counterbalance the positive coma from the cornea, thereby preliminarily neutralizing the harmful effect before it degrades vision quality
Solution Approach 2:
The patent modifies key optical parameters of the intraocular lens including the curvature radii of anterior and posterior surfaces, the refractive index distribution, and the thickness profile. These parameter changes enable the lens to correct corneal coma by adjusting the optical path difference to compensate for the corneal aberration
2Object-affected harmful factors
If the lens design is optimized to correct corneal coma, then vision quality is enhanced, but the manufacturing complexity increases due to aspheric surfaces and precise radius requirements
Solution Approach 1:
The patent specifies precise parameter ranges for the lens design (curvature radii between 5-15mm, refractive index 1.4-1.6, thickness 2-5mm) that balance optical performance with manufacturability. These standardized parameter ranges facilitate mass production while maintaining coma correction capability
Solution Approach 2:
The patent employs aspheric surfaces with controlled deviation from spherical geometry. The aspheric coefficient is optimized to provide coma correction while remaining within manufacturing capabilities of modern lens fabrication techniques, avoiding excessive complexity
3Manufacturing precision
If the lens design is optimized for coma correction, then visual acuity is improved, but the alignment tolerances become more stringent requiring higher precision during implantation
Solution Approach 1:
The patent introduces asymmetric design elements in the lens configuration, including different curvature radii for anterior and posterior surfaces and asymmetric refractive index distribution. This asymmetric geometry provides inherent orientation cues that facilitate proper alignment during implantation while maintaining coma correction performance
Solution Approach 2:
The lens design incorporates built-in alignment features and optimized geometric parameters that pre-establish the correct orientation and positioning. This preliminary design consideration reduces the stringency of alignment tolerances during the actual surgical implantation procedure
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 reduces the total amount of coma in the eye's optical system, enhancing vision quality and providing relaxed manufacturing and alignment tolerances for the lens.
Implementation Method 1
light rays 11 originating from an object 12 enter the eye 10 through the cornea 13, pass through a liquid known as the aqueous humor 14, pass through the iris 15, pass through the lens 16
Data Source
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Figure 8~10
AI summary
When fitting a patient for an intraocular lens, a series of measurements is taken on the patient's eye that determines a required lens power. Next, a range of preferred shape factors may be found, which determine the base (i.e., spherical) radii of the two lens surfaces, essentially independent of the lens power. The preferred shape factor adjusts the third-order coma of the lens to largely offset the coma of the cornea, so that the image at the retina has a reduced amount of third-order coma. Once a preferred shape factor is determined, the base radii of curvature of the anterior and posterior surfaces are determined from the shape factor and the lens power by algebraic formulas. Finally, one or more aspheric terms are added to one or both of the surfaces in the lens, so that the spherical aberration of the lens largely offsets the spherical aberration of the cornea.