Visual Axis-Centered Refractive Laser Ablation Pattern
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Solution Overview
Problem
Current refractive laser surgery methods for vision correction often fail to accurately center the ablation pattern on the visual axis, leading to suboptimal results, especially for individuals with significant variance between their line of sight and visual axis, as they rely on pupil-centered wavefront data which does not reflect the patient's actual physiological visual axis.
Innovation Solution
A method to reconstruct and shift ocular or corneal wavefront data to center the ablation pattern on the visual axis intersect of the cornea, using transformed Zernike coefficients and wavefront slope data from devices like Shack-Hartmann wavefront sensors, allowing for customized correction of spherocylindrical and higher-order aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the ablation pattern is centered on the pupil center along the line of sight, then the surgical procedure is simplified and easier to perform, but the alignment accuracy with the visual axis deteriorates leading to suboptimal vision correction results
Solution Approach 1:
The patent applies preliminary action by pre-calculating the displacement between the pupil center and visual axis intersection point using wavefront data before the ablation procedure. The ablation pattern is pre-shifted based on this calculated displacement, so that when the laser is centered on the pupil, the actual ablation occurs at the correct visual axis location. This resolves the contradiction by maintaining the ease of pupil-centered alignment while achieving visual axis precision through advance computational preparation.
2Device complexity
If wavefront data is collected centered on the pupil, then the measurement process is simplified, but the measurement precision of the visual axis aberrations deteriorates
Solution Approach 1:
The patent uses wavefront data as an intermediary element to bridge the gap between pupil-centered measurement simplicity and visual axis measurement precision. The wavefront data is collected from the pupil-centered measurement system, then mathematically processed to extract and shift the aberration information to the visual axis coordinate system. This intermediary approach allows the simple pupil-centered measurement process to yield precise visual axis aberration data.
3Manufacturing precision
If the ablation pattern is shifted to center on the visual axis, then the vision correction precision is improved, but the surgical procedure complexity increases
Solution Approach 1:
The patent replaces the mechanical approach of physically repositioning the laser or surgical apparatus to align with the visual axis with a computational approach. Instead of mechanically shifting the entire surgical system, the patent uses software-based coordinate transformation and pattern shifting of the ablation data. This substitution of mechanical complexity with computational processing maintains surgical simplicity while achieving visual axis precision.
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 accurate and personalized vision correction by aligning the ablation pattern with the visual axis, improving the precision of refractive surgery outcomes for patients with varying degrees of line of sight and visual axis disparity.
Implementation Method 1
the cornea is reshaped by excimer laser ablation of corneal tissue
Implementation Method 2
excimer laser ablation of corneal tissue
Implementation Method 3
a femtosecond laser is used to create both a flap and a lenticule of intrastromal corneal tissue, the latter of which is removed to provide the optical correction
Implementation Method 4
ocular wavefront data taken by a wavefront aberrometer, such as a Shack-Hartmann wavefront sensor
Data Source
AI summary
A method of performing refractive laser eye surgery on a human eye is provided wherein the ablation pattern is centered along the visual axis, rather than along the line of sight. First, a wavefront, either ocular, corneal or a combination thereof, is generated by a wavefront sensor centered along the line of sight. This measured wavefront is centered on and encompasses a patient's pupil. Then, an analysis pupil is determined which encompasses the measured pupil. The analysis pupil is centered along the visual axis at the point of intersection with the cornea. Consequently, the measured wavefront is reconstructed over the analysis pupil only using data taken over the area covered by the measured pupil. This reconstruction is done through a least squares fit of a series of slopes from the measured wavefront and/or through the transformation of aberration coefficients. Finally, an ablation pattern, or a lenticule generation pattern, to be performed by a refractive laser centered on the corneal intersect of the visual axis is produced in accordance with the reconstructed wavefront.