Corneal Laser Image Alignment via Limbus and Vessel Correlation
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Solution Overview
Problem
High-precision alignment of eye images for laser surgery is challenging due to pupil size and position variations, rotational symmetry of alignment markers, and the need for stable yet removable artificial marks, with existing methods lacking verification and adjustment capabilities.
Innovation Solution
A system and method that determine the limbus location and align it in two dimensions, use blood vessels as rotational references, perform correlation at multiple rotational positions, adjust contrast and brightness, and provide visual verification through animation and manual adjustment options to ensure optimal image alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the pupil is used as an alignment marker, then it is easy to find and align, but it varies in size and position making high-precision alignment difficult
Solution Approach 1:
The patent introduces the limbus as an intermediary alignment marker that is more stable than the pupil. The limbus provides a consistent anatomical reference point that does not change position or appearance with pupil dynamics, thereby mediating between the need for ease of identification and precision of alignment.
Solution Approach 2:
The patent changes the parameter being used for alignment from pupil characteristics (which vary dynamically) to limbus characteristics (which are stable). This parameter change from a dynamic marker to a static marker resolves the contradiction between ease of alignment and alignment precision.
2Measurement precision
If the limbus is used as an alignment marker, then it remains fixed between images, but it presents a soft boundary that changes appearance with illumination
Solution Approach 1:
The patent addresses the illumination sensitivity of the limbus by using image processing techniques that compensate for brightness and contrast variations. The system detects the limbus despite changes in appearance caused by different lighting conditions, effectively neutralizing the detection difficulty.
3Measurement precision
If artificial alignment marks are placed on the eye, then they provide stable and easily seen references, but they must be easily removed after surgery
Solution Approach 1:
The patent uses natural anatomical features (limbus and blood vessels) that already exist on the eye, eliminating the need for artificial markers. These natural features provide stable alignment references without requiring any additional materials to be applied or removed, thus serving the alignment function through the eye's own structures.
4Extent of automation
If algorithms are used for image alignment, then alignment assistance is provided, but the surgeon must manually confirm alignment before surgery
Solution Approach 1:
The patent implements an automated verification system that provides feedback to the surgeon regarding alignment quality. The system analyzes the alignment of anatomical features between pre-operative and intra-operative images, and only permits surgery to proceed when alignment meets predetermined criteria, thereby automating the verification process while maintaining safety.
Data Source
AI summary
A system and method for aligning a first and a second image of an eye includes making a determination of a limbus location on a first eye image and a second eye image. The limbus location of the first and the second eye images are then aligned in two dimensions. A second eye feature location is determined on the first and the second eye image. One of the first and the second eye image is relatively rotated, and a correlation is performed on the first and the second eye image at a plurality of relative rotational positions using the second eye feature location. From the correlation an optimal first and second image alignment is identified.