Corneal Thickness Measurement Using Slit Illumination and Ray-Tracing
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Solution Overview
Problem
Existing methods for determining corneal thickness are complex, costly, and prone to inaccuracies due to the need for multiple camera systems, assumptions about corneal surface symmetries, and uncertainties in eye position between image captures.
Innovation Solution
A method and apparatus using a plurality of stimulator point light sources to illuminate the cornea, capturing images to construct models of the anterior and posterior surfaces via ray-tracing, allowing for accurate determination of corneal thickness without assumptions about surface symmetries and with a single camera system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Placido ring illuminator is used to illuminate the cornea, then the corneal anterior surface can be imaged, but inaccuracies are introduced due to assumed symmetries in the corneal surface
Solution Approach 1:
The patent uses a slit-shaped illumination source instead of a Placido ring illuminator to avoid assuming symmetries in the corneal surface. The slit source creates an asymmetric illumination pattern that does not require the cornea to be symmetric, thereby eliminating inaccuracies introduced by symmetry assumptions while maintaining measurement precision.
2Adaptability or versatility
If two camera systems are used to focus on different planes (iris plane and cornea plane), then both surfaces can be imaged, but device complexity and cost increase
Solution Approach 1:
The patent combines the imaging of both the iris plane and cornea plane into a single camera system. By using a slit-shaped illumination source and appropriate optical arrangements, the single camera can capture images of both surfaces sequentially or simultaneously, thereby reducing device complexity and cost while maintaining full imaging capability.
Solution Approach 2:
The single camera system is designed to perform multiple functions: imaging the iris plane for corneal shape analysis and imaging the cornea plane for thickness measurement. This multi-functional approach eliminates the need for separate camera systems while preserving all necessary imaging capabilities.
3Measurement precision
If two images are captured sequentially to determine corneal thickness, then thickness can be calculated, but eye displacement between captures introduces uncertainty
Solution Approach 1:
The patent uses a slit-shaped illumination source to illuminate the cornea before the second image is captured. This preliminary illumination creates a reference pattern on the corneal surface that allows for accurate alignment and registration between the first and second images, even if the eye moves slightly between captures. The slit pattern serves as a stable reference that compensates for eye displacement, maintaining both precision and reliability.
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 provides a more accurate and cost-effective method for determining corneal thickness by establishing a one-to-one correspondence between light sources and image reflections, reducing complexity and errors associated with previous techniques.
Implementation Method 1
capturing an image of the cornea comprising reflected images of the stimulator point light sources
Implementation Method 2
constructing a second model representing a posterior surface of the cornea from the image by ray-tracing the reflected images of the stimulator point light sources towards the model representing the anterior surface of the cornea
Data Source
AI summary
A method of determining a corneal thickness and an apparatus for determining the same. The method comprises the following steps of illuminating a cornea by a plurality of stimulator point light sources, capturing an image of the cornea comprising reflected images of the stimulator point light sources, obtaining a first model representing an anterior surface of the cornea, constructing a second model representing a posterior surface of the cornea from the image by ray-tracing the reflected images of the stimulator point light sources towards the first model representing the anterior surface of the cornea, and determining the corneal thickness from the first model representing the anterior surface and the second model representing the posterior surface.