Purpose: There is an increasing number of reports in the literature about the possible influence of the peripheral refraction in myopia development. The aim of this work was to determine whether the peripheral refractive differences lead to changes in visual performance. We used a forced choice procedure to assess the speed and accuracy (visual processing) of people with and without myopia at detecting the direction of a Gabor patch presented at different retinal locations.
Methods: Visual processing was measured twice in random order at 6 retinal locations: 10, 20 and 30 degrees eccentricity at the temporal and at the nasal retina. We tested the dominant eye of 8 adults (aged 19 to 33 years) with moderate myopia (spherical equivalent ranging from -4.25 to -2.00 D) and 8 age-matched adults without myopia (spherical equivalent from -0.63 to 0.75 D). Participants’ task was to report via bottom press whether the Gabor patch, with suprathreshold contrast and spatial frequency, was tilted 30º to the right or to the left. The target was preceded by a 50 msec duration cue, exposed for variable periods of 10, 30, 60, 90 and 140 msec, selected in random order, and followed by a noise mask until response was given. For each block, processing time was determined using the method of constant stimuli based in 400 trials per retinal location (80 trials per exposure). Threshold was defined as the exposure time yielding 75% of correct responses; results were analysed using linear mixed models (SPSS, v18).
Results: The mean processing time in the group with myopia was 73 msec and in the group without myopia was 66 msec; the difference between groups was not statistically significant (p = 0.087). There was a statistically significant difference between the nasal and temporal retina, mean difference was 13 msec (p = 0.002) with smaller processing time in the nasal retina.
Conclusions: For the type of paradigm used in this study, there was no difference in processing time of the peripheral retina between people with and people without myopia. Despite extensive reports in the literature about different refraction patterns in this study we found evidences that this does not translate into functional changes.
2012. Vol. 53, no 14, 4830