Multi-Wavelength Eye Tracking for Refractive Surgery
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Solution Overview
Problem
Current eye tracking systems for refractive ophthalmic surgery face challenges in accurately registering and tracking the position of the eye due to poor contrast of essential features, especially blood vessels, and incorrect differentiation between vessels moving with the eye and those moving with the head, leading to inaccurate results and increased operation times.
Innovation Solution
The system uses different wavelengths of light to enhance contrast, with infrared light for the iris/pupil region and green light for scleral blood vessels, allowing for precise localization of translational and rotational displacements by calculating displacements between reference and momentary images, and employing image processing techniques such as subtraction and classification of blood vessels to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If markers are applied to the eye for tracking, then tracking accuracy is improved, but the markers may irritate the eye or require anesthesia and the attachment may not last much longer than one hour
Solution Approach 1:
The patent extracts the tracking function from physical markers and implements it through optical detection of natural eye features (iris, pupil, sclera, blood vessels) using multi-wavelength imaging. This eliminates the need for markers that cause irritation while maintaining tracking accuracy through computational analysis of anatomical landmarks.
Solution Approach 2:
The patent introduces light of different wavelengths as an intermediary to enhance the visibility and contrast of eye features without physical contact. By using infrared light for the iris/pupil region and green light for scleral blood vessels, the system achieves markerless tracking with high precision while avoiding eye irritation.
2Measurement precision
If pupil image tracking is used, then eye position can be monitored, but the exact position depends on refraction of light through the cornea which may change due to eye orientation, leading to artificial shift of image position
Solution Approach 1:
The patent applies local quality by using different wavelengths of light for different regions of the eye: infrared light (810-880 nm) for the iris and pupil region, and green light (520-570 nm) for the scleral blood vessels. This regional optimization enhances contrast and detection accuracy for each specific anatomical structure, compensating for refraction variations.
Solution Approach 2:
The patent changes the wavelength parameter of light to optimize detection of different eye features. By using infrared wavelengths for the iris/pupil and green wavelengths for blood vessels, the system overcomes the limitations of single-wavelength imaging and achieves more reliable tracking under varying eye orientations and refraction conditions.
3Ease of operation
If all eye features are illuminated by daylight with ordinary cameras, then all features are visible in color images, but the contrast of blood vessels is poor and localization is time-consuming
Solution Approach 1:
The patent changes the wavelength parameter from visible daylight to specific infrared and green wavelengths. This enables selective enhancement of different eye features: infrared light provides high contrast for the iris and pupil, while green light provides high contrast for scleral blood vessels, making their localization rapid and accurate.
Solution Approach 2:
The patent applies local quality by optimizing illumination for specific regions: using infrared illumination for the iris/pupil region and green illumination for the sclera with blood vessels. This regional optimization achieves high contrast for each feature type without requiring markers or complex procedures.
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 results in a faster and more accurate eye tracking system, capable of handling eye movements and head rotations, thereby improving the precision of laser application during refractive surgery and reducing operation time.
Implementation Method 1
a first light source system illuminating the iris and the pupil of the eye with light of a first wavelength, in particular with infrared (IR) light
Implementation Method 2
a second light source system illuminating the sclera of the eye with light of a second wavelength, in particular with green light
Implementation Method 3
a camera system sensitive to light of the first and the second wavelength
Data Source
AI summary
The invention refers to A system (10) for registering and tracking the position of a person's eye, in particular for refractive ophthalmic surgery. According to the invention, the system is designed such that eye images containing at least the iris and the pupil of the eye are made at a first wavelength of light and that eye images containing scleral blood vessels are made at a different second wavelength of light. The invention furthermore refers to a corresponding method for registering and tracking the position of a person's eye.