Ophthalmologic Microscope Orientation via Purkinje Reflections
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Solution Overview
Problem
In ophthalmology, determining the orientation of an ophthalmologic microscope device relative to an eye for precise measurements, such as corneal analysis and Purkinje reflection analysis, is challenging due to the need for accurate angle and position information.
Innovation Solution
A method involving sending light from a light source onto the eye, recording specular reflections, and processing their position in the image to determine orientation parameters like the angle of incidence or position of the apex, using a slit illumination and multiple light sources arranged around the optical axis to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the position of the apex of the eye is used to determine orientation, then the orientation parameter can be derived from the recorded image, but the position of the apex is generally not known a priori
Solution Approach 1:
The patent uses Purkinje reflections as an intermediary to indirectly determine the apex position. Instead of directly measuring the apex position (which is unknown), the system measures the positions of Purkinje reflections from known light sources and uses these as intermediate data points to calculate the apex position and orientation parameters through geometric relationships.
2Measurement precision
If quantitative analysis of corneal sectional views is performed, then precise orientation information is required, but obtaining accurate orientation data is challenging
Solution Approach 1:
The system uses the recorded positions of Purkinje reflections as feedback to iteratively refine the orientation parameter determination. By comparing the measured reflection positions with expected positions based on assumed orientation parameters, the system can adjust and optimize the orientation calculations to achieve higher precision in corneal analysis.
Solution Approach 2:
Purkinje reflections serve as intermediary markers that make the invisible orientation parameters visible and measurable. The reflections from known light source positions provide indirect information about the eye's orientation, transforming an abstract orientation measurement problem into a concrete position measurement problem that can be solved through image processing.
3Measurement precision
If multiple light sources are arranged around the optical axis, then accuracy of orientation determination is enhanced, but device complexity increases
Solution Approach 1:
The illumination system is segmented into multiple discrete light sources arranged around the optical axis, each contributing independent Purkinje reflection data. This segmentation allows the system to gather orientation information from multiple angles and positions, improving accuracy through redundant measurements while keeping each individual light source simple and manageable.
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
Enables efficient and accurate determination of orientation parameters, facilitating precise measurements of corneal thickness and curvature, and improving the analysis of Purkinje reflections for keratometric measurements.
Implementation Method 1
Viewing the eye through the microscope and recording an image comprising a specular reflection of the light from the eye. In other words, light is reflected from a mirroring surface or interface of the eye (Purkinje reflection)
Data Source
AI summary
In the device and method, the angle of incidence of slit light onto an eye to be examined is determined from its Purkinje reflection recorded in an image by measuring the offset from the reflection to the apex of the image of the cornea. In another embodiment, Purkinje reflections of light sources arranged around the optical axis of the microscope are correlated with a reference pattern of radial stripes in order to determine the offset between the optical axis and the apex of the eye.