Equal Conic Intraocular Lens Design for Aberration Control
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Solution Overview
Problem
Intraocular lenses (IOLs) designed to reduce spherical aberrations often fail to provide predictable vision outcomes in eyes that have undergone refractive surgery or have decentered or tilted lenses, as they do not maintain equal surface optics and consistent longitudinal ray aberrations across different powers.
Innovation Solution
A foldable IOL design with equal surfaces and zero added spherical aberrations, utilizing a conic constant optimization method to ensure consistent longitudinal ray aberrations across various powers, is developed, featuring an optical lens diameter of 5.75 mm, edge thickness of 0.35 mm, and a material index of refraction of 1.4585, balancing aberrations by adjusting the conic coefficient to intersect rays at specific heights within the lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an IOL is designed with negative spherical aberration to reduce the normal eye's total spherical aberrations, then spherical aberrations are reduced in ideal situations, but vision quality deteriorates in non-ideal situations such as refractive surgery eyes or decentered/tilted lenses
Solution Approach 1:
The patent changes the optical parameters of the IOL by introducing an aspheric conic surface with a specific conic constant (k=-1.23), transforming the lens from spherical to aspheric geometry. This parameter change enables the lens to reduce spherical aberration while maintaining equal surface optics, thereby improving both vision quality and tolerance to decenteration and tilt simultaneously
2Adaptability or versatility
If an IOL design adds very little positive spherical aberration to be tolerant of decentration and tilts, then adaptability improves, but the lens loses the benefit of equal surface optics and consistent longitudinal ray aberrations
Solution Approach 1:
The patent applies asymmetry by designing the IOL with equal but not identical surfaces - both surfaces have the same conic form but different radii of curvature. This asymmetric design with conic constant k=-1.23 allows the lens to maintain equal surface optics (same conic form) while achieving tolerance to decenteration and tilt, resolving the contradiction between adaptability and manufacturing precision
3Ease of manufacture
If different IOL powers are designed without standardized aberration characteristics, then each power can be optimized independently, but postoperative results become less predictable
Solution Approach 1:
The patent establishes a universal design standard where all IOL powers share the same conic constant (k=-1.23) and equal surface optics characteristics. This universal approach ensures that every IOL in the power range from -10 to +35 D has consistent longitudinal ray aberration properties, making postoperative results predictable while still allowing independent optimization of each power's focal characteristics
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 design achieves balanced longitudinal ray aberrations and reduced spherical aberrations, providing predictable vision outcomes and improved tolerance to decentration and tilts, maintaining the benefits of aspheric IOLs while ensuring equal surface optics across different lens powers.
Implementation Method 1
The surface can be quite complex and even designed for a specific eye. The goal of the IOL design is, of course, to provide the patient with good vision quality. This means that the optical aberrations (deviation from a perfect focus) should be small.
Implementation Method 2
If the lens is placed in the correct position and orientation in a normal eye, the spherical aberrations will be reduced as desired. More recently, there has been an effort to remove other (higher-order) aberrations, such as spherical aberrations, through the IOL design.
Data Source
AI summary
An intraocular lens, with equal conic surfaces, is intended to replace the crystalline lens in the posterior chamber of a patient's eye, in particular after a cataract extraction. The lens provides optical power to focus objects onto a patient's retina. In addition the lens surfaces are shaped to reduce optical aberrations at the retina and are tolerant to lens tilt and decentration within the eye. The lens is designed to have zero longitudinal ray aberrations at a specific ray height.