Abstract
Purpose :
Enhancing topographical features of the retina can emphasize clinically relevant features such as vessels and the optic nerve head. Using a fundus imager, we investigated the impact of a digital structured illumination analysis on visualization of topographical features in test targets and human eyes.
Methods :
We constructed reflectance and topographical maps from images obtained using prototype software on a CLARUSTM 700 (ZEISS, Dublin, CA). On this slit-scanning fundus imager, the stripe illumination of the retina is offset from the detection path in the pupil plane, resulting in a deflection of the observed stripe that can be converted to height of the retina. We enhanced the resolution with a structured illumination analysis, where we digitally converted the illumination to a sinusoidally weighted pattern and analyzed for phase shifts that characterize the deflection of the stripes. We analyzed images of a modified USAF test target with printed regions of varying reflectivity and paper folds to create topographical features. We also imaged human eyes and compared the enhanced topography map to the reflectance map.
Results :
In Fig. 1, the profile of the enhanced topography map shows the elevation change of the paper fold. While the fold can be seen in the reflectance map, the elevation change to the right of the fold is not evident by reflectance alone. Fig.1 also shows that feature reflectivity influences apparent depth information, as the printed features can still be visualized in the enhanced topography map. Fig. 2 displays a visual enhancement of vessels in a human eye in the enhanced topography map.
Conclusions :
Images with a visual enhancement of topographical features can be generated from a slit-scanning fundus imager. These enhancements could provide clinical utility by emphasizing important features, such as the optic disc and cup, elevations of the retina, vessels and vessel crossings, and tumors. Currently, feature reflectance influences the depth map, and we are exploring calibrations and system nonlinearities to separate the reflectance and topography further.
This is a 2020 Imaging in the Eye Conference abstract.