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Girish Kumar, Scott B. Stevenson, Austin Roorda; Saccadic targeting variability revealed by high magnification retinal imaging. Journal of Vision 2006;6(6):495. doi: 10.1167/6.6.495.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Measure eye movements while imaging the retina using the Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO), allowing accurate measurement of the variation of saccadic landing points to targets with small eccentricities.
Methods: Two subjects were imaged using the AOSLO with a 660 nm laser and a 1 degree field of view. Subjects were instructed to follow a 2 min of arc square that was jittered randomly among nine possible locations within the 1 degree field. Eye movements were extracted by cross-correlating sequential video frames and the retinal position of the fixation square was determined just before and just after each saccade. Variability in the retinal landing point of a target after a saccade and the magnitude of the retinal position error before a saccade were calculated.
Results: The starting and landing points of 78 and 104 saccades were measured for two subjects. The standard deviation of the landing points was 8.19 minutes of arc and 11.25 minutes of arc. Saccades to targets outside this zone were almost all corrective. Once a target landed within this zone, fixation often remained relatively steady.
Conclusions: Small saccades place targets within a zone that is smaller than the diameter of the foveola where the cone density is maximum, but is much larger than the diameter of a single cone in this zone.
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