Ocular Surface Shape Determination via Zonal Reconstruction
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Solution Overview
Problem
Existing ophthalmic systems face challenges in accurately determining the shape of ocular surfaces due to corneal irregularities and high spatial frequency content, as modal reconstructors like Zernike Polynomials lack sufficient fidelity unless extended to higher orders, leading to issues with uniform grid reconstruction.
Innovation Solution
A direct solution zonal reconstruction method that uses a combination of zonal reconstruction and polynomial fitting, employing a system with a light source, photodetector, and processor to determine the shape of ocular surfaces without relying on a uniform grid, allowing for more robust reconstruction and improved fidelity in capturing high spatial frequency features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If modal reconstructors (e.g., Zernike Polynomials) are used for wavefront reconstruction, then the method can handle arbitrary point locations, but the fidelity is insufficient for surfaces containing high spatial frequency content unless extended to include higher orders
Solution Approach 1:
The patent divides the corneal surface into multiple zones (e.g., paraxial zone, intermediate zone, peripheral zone) and applies different reconstruction methods to each zone. The paraxial zone uses modal reconstruction (Zernike polynomials) while peripheral zones use direct solution zonal reconstruction. This segmentation allows each method to operate in its optimal range, achieving both versatility and precision for high spatial frequency content.
Solution Approach 2:
Different reconstruction algorithms are applied to different regions of the corneal surface based on their specific characteristics. The patent applies modal reconstruction to the paraxial region where it performs well, and direct solution zonal reconstruction to peripheral regions with high spatial frequency content. This local differentiation optimizes the quality of reconstruction in each specific area.
2Ease of manufacture
If iterative methods in uniform space are used for wavefront reconstruction, then the reconstruction process can be simplified, but the method relies on a uniform grid of points which is not guaranteed by corneal irregularities
Solution Approach 1:
The patent segments the corneal surface into multiple zones with different reconstruction approaches. The direct solution zonal reconstruction method does not require a uniform grid and can handle arbitrary point distributions by using zonal coordinates and polynomial fitting in each zone, thereby maintaining reliability for irregular surfaces while simplifying the overall process through automated zone-based processing.
Solution Approach 2:
The patent transforms the reconstruction problem from uniform Cartesian coordinates to zonal coordinates adapted to the corneal surface geometry. By changing the coordinate system and using polynomial fitting in zonal spaces, the method eliminates the requirement for uniform grids while maintaining computational simplicity and accuracy for irregular corneal surfaces.
3Measurement precision
If higher order Zernike polynomials are used to improve fidelity for high spatial frequency content, then the measurement precision improves, but the device complexity and computational burden increase
Solution Approach 1:
Instead of using high-order Zernike polynomials across the entire corneal surface, the patent segments the surface into multiple zones and applies direct solution zonal reconstruction to peripheral zones. This approach captures high spatial frequency content locally without requiring globally high-order polynomial expansions, thereby reducing overall computational complexity while maintaining precision where needed.
Solution Approach 2:
The patent applies different levels of reconstruction complexity to different regions. High-order modal reconstruction is used only where necessary (paraxial zone), while direct solution zonal reconstruction with polynomial fitting is used in peripheral zones. This localized approach achieves high fidelity for high spatial frequency content without unnecessarily increasing computational complexity across the entire corneal surface.
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
This method effectively determines the shape of ocular surfaces, providing accurate input for treatment plans in refractive procedures like LASIK, PRK, and LASEK, with improved accuracy and convergence, especially in capturing high frequency content, as demonstrated by reduced RMS errors compared to traditional Zernike modal reconstructors.
Implementation Method 1
a light source including a plurality of light elements, a photodetector, an optical system for directing light from the light elements reflected by a surface of the eye onto the photodetector
Data Source
AI summary
Systems and methods for modifying an eye including a light source with light elements, a photodetector producing a signal representing images of the light elements and corresponding to locations on an ocular surface, an optical system directing light from the light elements reflected by the ocular surface onto the photodetector, a memory including code for processing the signal, and a processor for executing the code and outputting shape data for use in calculating a treatment plan for the eye. The code includes instructions for determining the shape data based on a combination of zonal reconstruction and polynomial fitting using the plurality of images.