Retinal topography using a fundus imager and structured-illumination approach

Abstract

Purpose : Three-dimensional surface topography of the retina can provide clinically relevant information for diagnosis and monitoring of disease. We investigated reconstruction of retinal three-dimensional topographical features using novel analyses of slit-scanning ophthalmoscopy data.

Methods : We reconstructed three-dimensional topography maps from human-eye images acquired with a CLARUS^TM 700 (ZEISS, Dublin, CA) fundus camera with prototype software and compared these to CIRRUS^TM 6000 (ZEISS, Dublin, CA) optical coherence tomography (OCT) scans. The fundus camera projects stripes onto the retina and records images of stripe illuminations while maintaining a small angle between illumination and imaging. Due to this angle, the stripe position in the image is directly related to the height of features on the retina. To enhance the height resolution, we applied a digital structured illumination approach – i.e. we manipulated the stripe illumination pattern by assigning sinusoidal weights to the individual stripe images, calculating a weighted sum, then analyzed retina height through phase shifts related to the location/deflection of the projected stripes. We varied the step-size between illuminations and compared topography maps generated through these analyses to OCT scans on the same eyes.

Results : Topography maps generated from the digitally structured illumination approach visually emphasize the height of structures on the retina. The resolution of the images is improved with smaller steps of the illumination, with a visible improvement comparing 1-pixel steps of the illumination to 8-pixel steps (see Figure 1). Comparison of the reconstructed topography maps to OCT data demonstrates common structural information for vessels and the optic nerve head.

Conclusions : Retinal topography maps can be generated from a digital structured illumination analysis of slit-scan fundus image data. This three-dimensional information can be useful for clinicians when characterizing morphology of the optic disc and cup, elevations of the retina, vessels and vessel crossings, tumors, and other retinal structures.

This is a 2020 ARVO Annual Meeting abstract.

 

Figure 1. Topography maps based on digital structured illumination analyses of slit-scanning fundus image data. Reconstructions based on 1-pixel steps between illuminations (top) show much higher resolution of structures on the retina than reconstructions based on 8-pixel steps (bottom).