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E. Pei, K. Holopigian, J. V. Odom, R. E. Carr; Motion Coherence Thresholds in Patients With Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1364.
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Patients with retinitis pigmentosa (RP) suffer from visual impairments, including peripheral visual field loss, poor visual acuity and impaired contrast sensitivity. Despite these losses, we have shown that patients with RP may perform normally on tasks that involve ‘higher-order’ processing. Here we extend those tests to include optic flow measures.
Patients with RP and age-similar control subjects were tested on motion discrimination tasks. The subjects were seated 40 cm from a display that subtended 42 x 54 degrees. Observers viewed a fixation target and pressed a mouse button to trigger the stimulus which was a pattern of white dots on a black background. Correct judgments about the motion resulted in a reduction in the number of dots moving in the same direction (coherently) and an increase in the number moving in other, randomly selected directions. A staircase procedure using a two-down, one-up rule was used to determine the coherence thresholds. On the optic flow tests, the task was to determine if the optic flow pattern originated from the right or left of fixation; for the rotational motion test, whether the rotational motion was in a clockwise or counterclockwise direction; for the motion direction task, whether the faster moving dots moved to the right or the left. For each task, two trials were obtained and the thresholds averaged; 95% confidence intervals were used to evaluate the results of the patients with RP.
Many of the patients with RP performed within normal limits on these tests of motion discrimination, even patients with poor visual acuity, constricted visual fields and/or non-recordable multifocal electroretinograms. The performance of the patients with RP was best for the motion direction discrimination task.
Patients with RP can perform within normal limits on tasks that involve motion judgments, especially if the discrimination is along the horizontal meridian and there is redundancy within the stimulus parameters. This supports previous findings from our laboratory that patients with RP can perform well on tasks that could relate to mobility and may provide helpful information regarding mobility training.
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