Purpose: To visualize retinal structures using a newly developed parallel line scanning ophthalmoscope (PLSO). Methods: A PLSO was built using a digital micro-mirror device (DMD) instead of traditional scanning mirrors to scan lines over the field of view (FOV). The DMD consists of 912 × 1140 micro-mirrors which can be individually switched on/off based on a programmed binary pattern. By switching on multiple (parallel) two-element wide lines in the DMD, the corresponding lines on the retina are imaged on a CMOS camera. After acquisition of each frame, the micro-mirrors are turned off and the mirrors for the next set of adjacent lines are turned on. This is repeated until the whole FOV is imaged. Confocal images are generated from the data by subtracting the maximum and minimum intensity values for each pixel in the sequence. The fovea and optic nerve head (ONH) of a healthy subject were imaged using 10º × 10º FOV at 100 Hz with 7 parallel lines resulting in a full image frame rate of 1.4 fps. The images were acquired through a dark-adapted pupil without any dilatation. The acquired data were processed into confocal images as well as non-confocal images (by averaging all frames). Results: The non-confocal images show a strong uniform background, which originates from the corneal scattering and the multiple-scattered light from the retinal tissue making the features of the retina almost undetectable. In the confocal images, confocality and contrast are drastically improved and the foveal avascular zone and smaller blood vessels are visible in the fovea image. Additionally the quality of the ONH image is improved and many of the main features can be distinguished such as the small blood vessels. Conclusions: The PLSO provided high contrast images of the fovea and ONH and detailed retinal structures could be observed. The use of a DMD eliminates moving parts from the system and exposure time for each frame is shorter than in full-field imaging, which reduces intra-frame motion. In retinal imaging, such a setup will provide better images because higher imaging speeds reduce motion artifacts.
11 Jun 2016
Young Researcher Vision Camp 2016: "See & Hear"