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Girish Kumar, Susana Chung; Functional Consequences of Slow Drift Fixational Eye Movements in Patients with Central Vision Loss. Journal of Vision 2015;15(12):72. doi: 10.1167/15.12.72.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have shown differences in fixation eye movement (FEM) behavior between normally sighted individuals and subjects with central vision loss (CVL), but there is no evidence of any functional consequences of these differences on vision. A recent theory posits a possible function for the slow drift component of FEM - to decrease the redundancy in retinal image sequences (ie. 'whitening'). Because patients with CVL exhibit greater slow drift amplitudes, in this study, our goal was to determine if the slow drift behavior of patients also whitens image sequences. To answer this question we used the Rodenstock Scanning Laser Ophthalmoscope to image the retinas of 16 young normal subjects, 14 older normal subjects and 17 CVL patients while they fixated a 1 degree cross for 30 seconds. Eye movements were recovered from the digitized image sequences using a brute-force cross-crorrelation algorithm, at a sampling frequency of 540Hz, from which we extracted a 100 millisecond saccade-free segment from each image sequence. Simulated natural scene movies were created with these saccade-free segments. Spatio-temporal amplitude spectra were calculated from the simulated movies. Across the three subject groups (young-normal, older-normal and CVL), fixation stability (based only on slow drift components) measured using the Bivariate Contour Ellipse Area were statistically different, and ranged from 19.32±33.14 to 162.01±240.86 square arc minutes. If there was a decrease in redundancy due to the slow drifts, the slope of the amplitude spectrum would be shallower for a movie than for the static natural image that created the movie. The change in slope ranged from 84.06%±7.33 to 89.29%±12.8, and were not statistically different, across our three subject groups. Our results suggest that the slow drift behavior of patients with CVL does not have any consequential effects on the whitening of natural image sequences that are incident on the retina.
Meeting abstract presented at VSS 2015
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