AS-OCT Pupillary Axis Alignment for Scleral Spur Visibility
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Solution Overview
Problem
Conventional OCT imaging systems face challenges in accurately locating and measuring the scleral spur due to varying visibility and contrast of its opposing portions in anterior segment OCT images, often resulting from misalignment between the visual and pupillary axes, which complicates geometric measurements.
Innovation Solution
The system aligns the pupillary axis of the eye with the axial imaging direction of the OCT imaging system by using a fixation target during image acquisition, ensuring accurate alignment and equalizing the contrast of scleral spur representations in the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional OCT imaging systems capture full anterior chamber images without alignment control, then data capture efficiency is improved, but scleral spur visibility and contrast become uneven
Solution Approach 1:
The system performs preliminary alignment by presenting a fixation target to the patient before image acquisition, ensuring the pupillary axis is aligned with the imaging system's optical axis. This preliminary action prevents the misalignment problem from occurring during the actual imaging process, maintaining both efficiency and measurement precision.
2Ease of operation
If the visual axis is used for alignment instead of the pupillary axis, then image acquisition is simplified, but scleral spur representations show unequal contrast
Solution Approach 1:
The system changes the alignment parameter from visual axis to pupillary axis. By using the pupillary axis (which passes through the center of the pupil) as the alignment reference instead of the visual axis, the system achieves equal contrast in scleral spur representations on both sides of the anterior chamber, improving measurement precision.
3Device complexity
If no fixation target is used, then device complexity is reduced, but alignment accuracy between pupillary and visual axes deteriorates
Solution Approach 1:
The fixation target serves as an intermediary element that facilitates accurate alignment. By providing a visual reference point for the patient to fixate upon, the system enables precise alignment of the pupillary axis with the imaging system's optical axis without significantly increasing overall device complexity.
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 alignment improves the visibility and contrast of scleral spur representations, enabling more precise geometric measurements of the anterior segment, such as ACW, LV, AOD, ACD, ACA, TIA, and TISA, by reducing tilt and enhancing the accuracy of landmark identification.
Implementation Method 1
Optical coherence tomography (OCT) is an imaging technique based on low-coherence interferometry, which is widely used to acquire high-resolution two- and three-dimensional images of optical scattering media
Implementation Method 2
In SD-OCT, a broadband light source delivers many wavelengths to the imaging target, and all wavelengths are measured simultaneously using a spectrometer as the detector
Implementation Method 3
A line-scan OCT imaging system acquires OCT data by scanning a focused line of light across the surface of the imaging target. Measured reflectance from the imaging target is used to generate OCT data comprising a two-dimensional reflectance profile
Data Source
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AI summary
A system arranged to process an anterior-segment optical coherence tomography, AS-OCT, image comprising representations of portions of a scleral spur of an eye to obtain a geometric measurement of the eye, comprising data processing hardware arranged to: process the AS-OCT image to acquire respective locations in the AS-OCT image of the representations of the portions of the scleral spur of the eye in the AS-OCT image; and obtain the geometric measurement based on the acquired locations. The system further comprises an OCT imaging system which is operable to acquire the AS-OCT image and comprises a fixation target to fix a gaze direction of the eye during acquisition of the AS-OCT image such that an axis in the AS-OCT image corresponding to a pupillary axis of the eye is aligned with a direction in the AS-OCT image corresponding to an axial imaging direction of the OCT imaging system.