Lenticule Thickness Profile for Vision Correction Stability
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Solution Overview
Problem
Current treatment devices for surgical correction of defective vision face challenges with regression due to post-operative epithelialization at the edge of the optical zone, particularly for hyperopia corrections, which limits the residual stromal thickness and restricts further corrections, affecting both hyperopia and myopia corrections.
Innovation Solution
A treatment device with a controller that determines a lenticule-shaped intended volume for corneal tissue removal, where the thickness is smaller than a comparison volume, allowing for greater correction in the center of the optical zone than at the edge, reducing maximum cutting depth and potential regression, and adjusting for spherical aberrations and higher-order aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large optical zone is used to avoid regression, then regression due to post-operative epithelialization is reduced, but the cutting depth increases and residual stromal thickness becomes insufficient
Solution Approach 1:
The patent applies local quality by creating a non-uniform thickness profile for the lenticule, where the thickness varies across different zones. The center region has greater thickness for stronger correction, while the peripheral region has reduced thickness to minimize regression. This spatial variation in thickness distributes the correction effect differently across the optical zone, addressing both the need for adequate correction depth and the need to reduce peripheral regression.
2Manufacturing precision
If the lenticule thickness is increased to achieve desired correction, then the correction effectiveness improves, but the residual stromal thickness decreases and further corrections are restricted
Solution Approach 1:
The patent implements local quality by designing a lenticule with spatially varying thickness, concentrating the correction effect in the central region where it is most needed for visual acuity, while reducing thickness at the periphery. This allows achieving the desired correction precision in the optical zone without uniformly increasing the total lenticule volume, thereby preserving more residual stromal thickness.
Solution Approach 2:
The patent applies parameter changes by modifying the thickness parameter of the lenticule across different spatial locations. Instead of using a uniform thickness, the thickness parameter is varied as a function of radial distance from the center, with the peripheral thickness being reduced relative to the central thickness. This parameter variation enables precise control over the correction effect while managing residual stromal thickness.
3Reliability
If the optical zone is enlarged to prevent regression, then correction stability improves, but the device complexity and treatment time increase
Solution Approach 1:
The patent resolves this contradiction by applying local quality through a tailored thickness profile that concentrates correction in the central optical zone while reducing peripheral intervention. This approach achieves correction stability without requiring an unnecessarily large optical zone, thereby simplifying the treatment design and reducing device complexity compared to uniform large-zone approaches.
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 approach enables more precise correction of defective vision in the center of the optical zone with minimal undercorrection at the edge, reducing regression and allowing for larger possible corrections within the same residual stromal thickness, enhancing the effectiveness of hyperopia and myopia treatments.
Implementation Method 1
the laser apparatus cuts corneal tissue by irradiation with laser radiation
Data Source
AI summary
A treatment device for the surgical correction of defective vision in an eye. The device includes a laser apparatus controlled by a controller. The controller determines a desired correction of defective vision from measurement data of the eye to produce control data for the laser, and to control the laser to emit radiation according to the control data, such that a lenticule-shaped volume is isolated in the cornea. The controller computes a lenticule-shaped intended volume, the removal of which from the cornea leads to an actual correction of defective vision in an optical zone in the eye which differs from the desired correction more at the edge of the optical zone than at the center of the optical zone. The thickness of the lenticule-shaped intended volume is less than the thickness of a lenticule-shaped comparison volume, the removal of which would bring about the desired correction of defective vision.