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A machine vision method for automated alignment of fundus imaging systems
Michele Moscaritolo1, Frederick P Knezevich, Ingrid Zimmer-Galler
1Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA.
Summary
A new parallax optical alignment method accurately tracks the pupil center in three axes for fundus imaging. This system enables rapid, precise alignment with minimal operator intervention, improving ophthalmic imaging procedures.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Optical Systems
Background:
- Accurate pupil tracking is crucial for precise fundus imaging.
- Existing methods may require pharmacologic dilation or lack multi-axis capability.
- Developing non-invasive, rapid pupil alignment techniques is essential for clinical efficiency.
Purpose of the Study:
- To present a novel method for simultaneous three-axis pupil tracking.
- To enable pre-imaging alignment for fundus photography.
- To assess the accuracy and efficiency of the developed tracking system.
Main Methods:
- Utilized parallax optical alignment with two cameras capturing pupil images from distinct directions.
- Developed an operator-supervised algorithm to determine pupil center coordinates.
- Employed a three-axis computer-controlled stage for precise alignment.
- Tested the system on 45 individuals (26 with glaucoma, 19 without) without pupil dilation.
Main Results:
- Achieved high accuracy in pupil center determination with variability of ±0.19 mm (vertical) and ±0.33 mm (horizontal).
- The algorithm processed pupil images rapidly, with a processing time of 0.75 msec.
- The tracking system successfully converged within a ±0.5 mm tolerance in all tested eyes (45/45).
Conclusions:
- The developed pupil tracking system offers rapid and accurate alignment for fundus imaging.
- The method minimizes operator intervention, enhancing clinical workflow efficiency.
- Image acquisition and processing of pupil images are effective for pre-imaging alignment.
