Abstract
Purpose :
To investigate how the function of ON and OFF visual pathways is affected by myopic refractive error, axial length, and eccentricity.
Methods :
Eleven eyes of 11 human subjects (23-30 years old; mean 25.9 +/- 1.9) were tested at 8 Michelson contrast levels (5-20%) out to 30 degrees from fixation.
A single test comprised of 579 trials (27 catch trials), at 92 locations, repeated 3 times for both light and dark stimuli. Each participant completed eight tests (4,632 trials).
Hardware consisted of a head mounted display with an eye tracker (HTC VIVE embedded Tobii) with a refresh rate of 90 Hz, a maximum luminance of 110 cd/m2. Stimuli were light or dark squares on a spherical binary noise background. Stimulus size was increased as a function of eccentricity using a power law relationship.
Unity (version 2017) software was used to generate the stimuli. Eye movements were measured at 120 Hz and restricted within a central 2.5-degree radius circle. Percent of correct responses were measured across the entire visual field and, separately, for each of 6 annual eccentricities 5-10, 11-20, 21-30 degrees from fixation. Percent response errors were plotted as a function of refractive error and axial length for the entire 30 degrees and for each specific eccentricity.
Results :
There was no statistically significant correlation between refractive error and percent response errors at any eccentricity or combined over the entire testing area (maximum r value = 0.4015, p = 0.064, between 21-30 degrees). There was a significant positive correlation between axial length and percent response errors across the entire testing area (r= 0.5198, p=0.0132). This was most pronounced at 21-30 eccentricity (r=0.583, p=0.0044). Overall, subjects responded more accurately for dark than light stimuli (14.38 ±8.11 versus 15.98 ± 8.59, p= 0.0127. This was most pronounced at 21-30 eccentricity (p=0.0049).
Conclusions :
Decreased accuracy to ON-OFF perimetric stimuli in myopic patients is more closely correlated to axial length than refractive error.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.