Ophthalmic OCT Magnification Correction for Normative Data Accuracy
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Solution Overview
Problem
Existing OCT-based ophthalmic examinations face inaccuracies in normative data comparative analysis due to variations in axial length and refractive power of subjects' eyes, leading to false positives or negatives in layer thickness assessments, particularly in glaucoma diagnosis, which conventional magnification correction techniques cannot address without external devices.
Innovation Solution
An ophthalmic apparatus that includes alignment based on Purkinje images or anterior eye segment images to estimate axial length and diopter, combined with focus adjustment and optical path length correction, to calculate magnification correction values for accurate OCT scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If OCT scan is performed under a fixed scan condition, then the scan area size is consistent, but the actual scanned area in the eye fundus varies due to different axial lengths and refractive powers
Solution Approach 1:
The patent applies magnification correction by calculating correction coefficients based on the subject's axial length and refractive power parameters. These parameters are used to adjust the scan area mapping, transforming the fixed scan condition into a subject-specific corrected scan that accounts for individual anatomical variations, thereby resolving the contradiction between scan consistency and measurement accuracy
Solution Approach 2:
The patent introduces an intermediary magnification correction process that acts between the fixed OCT scan and the layer thickness measurement. This correction process uses axial length and refractive power as intermediate variables to compute correction coefficients, which then adjust the scan area interpretation to achieve accurate layer thickness measurements despite fixed scan conditions
2Adaptability or versatility
If normative data is prepared for a predetermined area of eye fundus, then the comparison framework is standardized, but false positives or negatives occur when axial length differs from standard
Solution Approach 1:
The patent modifies the normative data comparison by applying magnification correction coefficients derived from the subject's specific axial length and refractive power. This parameter-based correction adapts the standardized normative data framework to individual subject variations, preventing false positives and negatives while maintaining the standardized comparison approach
Solution Approach 2:
The patent performs preliminary magnification correction before conducting the normative data comparison. By pre-calculating correction coefficients based on axial length and refractive power and applying them to the scan area mapping beforehand, the system ensures that the subsequent comparison with standardized normative data is performed on corrected, accurate measurements, thereby eliminating diagnostic errors
3Measurement precision
If external devices are used for magnification correction, then correction accuracy can be improved, but device complexity and operational requirements increase
Solution Approach 1:
The patent merges the magnification correction function into the OCT apparatus itself by integrating axial length and refractive power measurement capabilities directly into the existing system. This consolidation eliminates the need for separate external devices while achieving the same correction accuracy, thereby reducing device complexity and operational requirements
Solution Approach 2:
The patent makes the OCT apparatus multi-functional by enabling it to perform both standard OCT imaging and axial length/refractive power measurements required for magnification correction. This universal approach allows a single device to accomplish multiple functions that previously required separate specialized instruments, simplifying the overall system configuration
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 precise alignment and magnification correction, ensuring accurate comparison of layer thickness distributions between subject and normative data, reducing false positives and negatives in diagnostic imaging.
Implementation Method 1
alignment based on Purkinje images or anterior eye segment images
Implementation Method 2
optical coherence tomography (OCT)... the optical path length of measurement light and the optical path length of reference light when the three dimensional data has been acquired
Data Source
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AI summary
An ophthalmic apparatus (1) of an embodiment include a data acquisition device (100), distribution data generator (231), correction value calculator (232), magnification corrector (233), and data comparator (234). The data acquisition device (100) acquires three dimensional data by applying OCT to the fundus (Ef) of a subject's eye (E). The distribution data generator (231) generates distribution data (300) of a predetermined measurement value in the fundus based on the three dimensional data. The correction value calculator (232) calculates a magnification correction value based on a predetermined condition for acquiring the three dimensional data. The magnification corrector (233) changes at least one of the size of standard distribution data (400) generated in advance for the predetermined measurement value and the size of the distribution data (300), based on the magnification correction value. The data comparator (234) compares the distribution data (300) with the standard distribution data (400), at least one of whose sizes has been changed by the magnification corrector (233).