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Kalina Burnat, Michal Wieteska, Anna Kozak; Shape defined by motion discrimination task allows to delineate peripheral from central visual processing.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1278. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
After central retinal loss in macular degeneration (MD), the description of perceptual deficits is limited to the central vision attributes, such as acuity. However, surprisingly in MD the peripheral motion processing is reinforced (Burnat et al., 2017). The authors report in control subject’s psychophysical measurements performed in full visual field as opposed to restricted to 10 deg viewing condition and in two patients with Retinitis Pigmentosa (RP).
8 controls, and 2 RP patients with visual field restriction up to 10 deg (age range 27-50, both sexes) were examined.The positive stimulus, S+ was a circle and the negative stimulus, S- was an ellipse surface matched with S+. The difficulty of the task depended on a staircase procedure in which the aspect ratio of the ellipse’s dimensions, depending on the subject’s response, could vary from 0,2 to nearly 1. The initial level of the difficulty was determined using plain grey S+/- on the bright background (Bcg). In shape from motion tasks, S+/- were built from the random dot kinetograms (RDKs) placed on the Bcg differing from the S+/- in one of the motion cues: coherence (S+/- 0%, Bcg 100%), direction (S+/- upward, Bcg horizontal leftward) and velocity (S+/- 10 deg/s, Bcg 20 deg/s). Two luminance sets of RDKs were tested: black dots on white background or reverse.
In general: discrimination of motion defined shapes independently of motion cue was more difficult when motion signal was carried by black dots, as compared to white. Coherence cue was the easiest for all subjects. The velocity cue was the most difficult, and differentiated in control subjects central 10 deg viewing condition from the full view. At the full viewing condition, black motion signal was significantly more difficult as compared to white motion, as shown by the thresholds calculated for the difference between ellipse height and circle diameter (for black: 1,7 – 0,22 deg, white: 0,32 – 0,09 deg). Interestingly white motion signal was perceived as more difficult in the 10 deg viewing condition as compared to full view. We could differentiate RP from control subjects only with dark motion signal at restricted to 10 deg. visual condition.
Peripheral motion stimulation by high contrast dark signal has strong influence on central processing. Tasks measuring simultaneously central and peripheral vision allow full assessments of vision loss.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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