Date of Award

Summer 8-16-2016

Degree Type

Thesis (On-Campus Access Only)

Degree Name

Master of Science in Vision Science

Committee Chair

Dr. Yang, Shun-Nan

Second Advisor

Dr. James Sheedy

Third Advisor

Dr. John Hayes

Abstract

Human motion perception relies on photoreceptors with varied chromatic sensitivity and spatial distribution. The study examined whether distinct chromatic filters afford different abilities in discerning motion stimuli presented at various eccentricities of the retinal periphery. To this end, twenty-six participants (14 males and 12 females, 24.3 ± 1.94 year of age) with normal (better than 20/30) monocular far acuity (-0.01 ± 0.08 logMAR) and color vision were asked to fixate the center of a screen while a peripheral motion target (black and white vertical grating bars) was briefly presented on a second curved, perpendicularly-viewed screen. Accuracy and latency of discriminating the direction of motion stimulus (1.5 cycle/° spatial frequency and 2° angular extent at 2-meter distance) presented on the left horizontal meridian (25° to 55° in 5° increments) were measured. In each of 5 blocks of trials, one of five chromatic filters with distinct peak spectrum (neutral density, red 620 nm, Yellow 620 nm, green 500 nm and blue 420 nm) but similar luminance transmittance was utilized to alter the chromatic spectrum of target stimuli. Results showed significant main effect of eccentricity (F [4, 440.174] = 80.351; p < 0.0001; F [4, 440.152] = 26.708; p < 0.0001 for accuracy and response time respectively), marginal main effect of chromatic filter (F [4, 440.014] = 2.19; p = 0.069; F [4, 440.094] = 2.059; p = 0.085), but no interaction between them (F [16, 440.063] = 0.805; p = 0.68; F [16, 440.112] = 0.708; p = 0.79). There was marginally shorter response time with red (Mean = 2.97; SE = 0.018) than blue (Mean = 2.984; SE = 0.018; p = 0.058) and yellow (Mean = 2.986; SE = 0.018; p = 0.029) filters. In addition, response accuracy for the neutral density filter matched the highest accuracy for all chromatic filters (red at near and blue at far), but response time for the neutral density filter matched the shortest one for the chromatic filters (red at most eccentricities). Chromatic filters might affect motion discrimination by selectively activating different color opponency pathways. Response accuracy is higher for S-cone On pathway than M- and L-cone ones at greater eccentricities. Response time however could be determined by L-cones because of their greater processing speed. These findings are important for the design of ophthalmic devices aimed to maximize the peripheral motion for active wearers.

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