Abstract
Purpose :
Contrast polarity was suggested as an important factor for myopia progression during tasks such as reading (Aleman et al., 2018). Stoimenova (2007) reported a difference in contrast sensitivity between adult myopes and emmetropes that was more pronounced with black-on-white tasks (B-on-W, OFF-pathway dominance) than white-on-black tasks (W-on-B, ON-pathway dominance). We hypothesized that this difference would be magnified when the myopes are uncorrected. This prospective study evaluates the difference between W-on-B and B-on-W distance visual acuity in myopic children corrected and uncorrected.
Methods :
Two groups of children aged 8 to 12 (mean= 9.58±1.16) were enrolled: Myopic group and non-myopic control group (emmetrope/best-corrected hyperope). The myopic group had refractive error between -0.75D and -6.00D of spherical equivalent. All subjects had a stereoacuity of at least 100 seconds of arc. The E-ETDRS visual acuity test with two contrast polarities (B-on-W and W-on-B) was used, which presented visual acuity ranging from 20/400 to 20/10 using single isolated optotypes with crowding bars. The order of contrast polarity presented was randomized. The tests were performed monocularly at 3 meters under both best-corrected and uncorrected conditions. After 30 minutes, another round of tests was performed. Visual acuities in letters (5 letters = 1 logMAR line) were averaged for two rounds and compared within the group between two polarities with paired t-tests, and between groups with ANOVA.
Results :
When optically corrected, the myopic eyes showed similar visual acuities with the two polarities (79.92±7.30 for W-on-B vs. 79.83±7.58 for B-on-W, t= -0.85, p= 0.41, Fig 1a). The control group also showed similar visual acuities with the two polarities (87.79±4.51 for W-on-B vs. 88.64±4.65 for B-on-W, t =-1.47, p= 0.16, Fig 1a), but better visual acuity than corrected myopes (F= 11.28, p= 0.0026 for W-on-B and F= 13.18, p= 0.0013 for B-on-W). However, when uncorrected, the visual acuity in the myopic group was significantly higher in W-on-B than B-on-W (58.00±18.97 vs. 51.83±19.04, t= 3.44, p= 0.0055, Fig 1b), and the difference was equivalent to 1.2 lines of logMAR.
Conclusions :
According to our pilot data, uncorrected myopes show poorer visual acuity with B-on-W than W-on-B visual acuity tests. This finding indicates that uncorrected myopia affects spatial resolution of OFF more than ON visual pathways.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.