Axial-Length-Based OCT Depth Control to Prevent Image Folding
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Solution Overview
Problem
Conventional ophthalmic apparatuses with OCT function face issues with optical path length adjustment due to individual eye size and shape differences, leading to image folding and increased examination time, particularly in myopic eyes.
Innovation Solution
An ophthalmic apparatus with an interferometer, OCT data generating unit, and optical path length changing unit, controlled by a processing unit to set a standard depth level based on ocular parameters, ensuring that partial data corresponding to specific eye fundus tissues are positioned at optimal levels within the image frame, preventing fold-over artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed standard depth level is used for optical path length adjustment, then the optical path length control is simple, but image folding occurs in eyes with long axial length (myopia)
Solution Approach 1:
The patent makes the standard depth level dynamic by setting it based on the axial length of the subject's eye. The processing unit determines the standard depth level according to the measured axial length, allowing the system to adapt to individual eye variations. This dynamic adjustment prevents image folding in myopic eyes while maintaining simple optical path length control mechanisms.
Solution Approach 2:
The patent changes the parameter of standard depth level based on the axial length measurement. By establishing a relationship between axial length and standard depth level, the system adjusts the depth level parameter to match individual eye characteristics. This parameter change approach resolves the contradiction by enabling accurate image depiction without requiring complex hardware modifications.
2Manufacturing precision
If measurement is conducted to set standard depth level according to individual eye differences, then image depiction accuracy is improved, but examination time and subject burden increase
Solution Approach 1:
The patent performs preliminary measurement of the axial length before optical path length adjustment. By acquiring the axial length information in advance, the system can determine the appropriate standard depth level prior to the main OCT imaging process. This preliminary action enables accurate individualized depth level setting without significantly extending the overall examination time, as the axial length measurement is a standard preliminary step in eye examinations.
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
The solution effectively adjusts the optical path length to prevent image folding, improving image quality and reducing examination time by optimizing the depiction of eye fundus tissues within the frame, particularly in myopic eyes.
Implementation Method 1
OCT is generally an imaging technique for reconstructing a high-resolution image by taking out a signal from the inside of optical scattering media (e.g., biological tissue) using optical interference. An OCT apparatus includes an interferometer having a measurement arm and a reference arm
Data Source
AI summary
An ophthalmic apparatus of an aspect example applies optical coherence tomography (OCT) to an eye, and includes an interferometer, an OCT data generating unit, an optical path length changing unit, and a processing unit. The interferometer includes a measurement arm and a reference arm. The OCT data generating unit is configured to generate OCT data based on an output from the interferometer. The optical path length changing unit is configured to change at least one of the optical path length of the measurement arm and the optical path length of the reference arm. The processing unit is configured to control the optical path length changing unit to place partial data of the OCT data corresponding to a predetermined part of the eye at a standard depth level. The standard depth level is set based on a predetermined ocular parameter value.