Abstract
Retinal motion detection with an accuracy of 0.77 arcmin corresponding to 3.7 µm on the retina is demonstrated with a novel digital micromirror device based ophthalmoscope. By generating a confocal image as a reference, eye motion could be measured from consecutively measured subsampled frames. The subsampled frames provide 7.7 millisecond snapshots of the retina without motion artifacts between the image points of the subsampled frame, distributed over the full field of view. An ophthalmoscope pattern projection speed of 130 Hz enabled a motion detection bandwidth of 65 Hz. A model eye with a scanning mirror was built to test the performance of the motion detection algorithm. Furthermore, an in vivo motion trace was obtained from a healthy volunteer. The obtained eye motion trace clearly shows the three main types of fixational eye movements. Lastly, the obtained eye motion trace was used to correct for the eye motion in consecutively obtained subsampled frames to produce an averaged confocal image correct for motion artefacts.
Highlights
To perceive the stationary world, our eyes keep moving constantly
This displacement information can be used to adjust the position of each subsampled frame with respect to the reference frame and generate an averaged confocal image that is corrected for motion
We have demonstrated the feasibility of eye motion detection in our DMDbased ophthalmoscope
Summary
To perceive the stationary world, our eyes keep moving constantly. Even when fixating, the eyes continue to move, causing the image of the fixated object to sweep across hundreds of photoreceptors [1,2,3]. A dithering probing beam and servo tracking system detected the eye motion by monitoring phase changes in the fundus reflectance of a specific feature such as the optic nerve head (ONH) with a reported tracking bandwidth of up to 1 kHz. In image-based approaches such as SLO, consecutive frames are compared to a template ( known as the reference frame) to obtain the translational shift between consecutive images. The subsampled snapshots provide simultaneously acquired points distributed over the full field of view (FOV) within an integration time of 7.7 milliseconds, eliminating motion artifacts in the relative position of these points With this proof-of-principle approach, retinal information is obtained simultaneously within the whole FOV, unlike the stripe-based raster-scan methods where the data is always acquired in a serial manner, and where motion artifacts can be present within the stripe. A cross-correlation analysis was performed to obtain the translational motion using the subsampled snapshots of the retina
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