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Esther G Gonzalez, Luminita Tarita-Nistor, Efrem Mandelcorn, Martin J Steinbach; Horizontal and vertical smooth pursuit in patients with central vision loss. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4690.
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For patients with age-related macular degeneration (AMD) and controls with normal vision, we examined the closed-loop gain of horizontal and vertical smooth pursuit eye movements as a function of stimulus speed and direction. We hypothesized that the smooth pursuit gain functions would be affected by stimulus speed and by the location of the preferred retinal locus (PRL) in relation to the scotoma as determined by microperimetry. Specifically, that a PRL on the left of the scotoma in the visual field would decrease the rightward gain as compared to the leftward gain and that a PRL below the scotoma in the visual field would decrease the upward gain relative to the downward gain.
Ten patients and 15 controls were tested in a step-ramp procedure with direction (left/right for horizontal motion; up/down for vertical motion), speed (5, 10, 15, 20 and 30 deg/sec) and 5 replication conditions randomized and blocked by orientation (horizontal vs vertical). Eye movements were binocularly recorded at 120 Hz. The weighted mean closed loop gain of smooth pursuit was obtained after saccades, blinks and artifacts were removed from the records. PRL location was determined with the MP-1 microperimeter.
Three PRL locations (near central, left and above the scotoma on the retina) were found in the better eye of the patient group. Overall, horizontal pursuit had a higher gain than vertical pursuit (p = 0.04 controls; p = 0.02 AMD). For the patients, the two eyes (better and worse) moved conjugately and had similar smooth pursuit gains in all tasks (p = 0.31 horizontal; p = 0.13 vertical). Regardless of PRL location, for horizontal pursuit all patients showed significantly better pursuit of leftward as compared to rightward motion (p = 0.004). For vertical pursuit, the patients’ downward pursuit also exhibited a higher gain than their upward pursuit (p = 0.02). The controls’ data did not exhibit a directional preponderance in either horizontal or vertical smooth pursuit (p > 0.05).
The PRL location was not predictive of the directional preponderance of pursuit performance. These results imply that patients may not use the PRL that was initially located during a static fixation task. Rather, they may adapt to the task by using a PRL that appears more suitable.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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