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Yueh-Hsun Wu, Hunter Throndsen, Gordon E Legge; Blur Tolerance in Myopes and Emmetropes. Invest. Ophthalmol. Vis. Sci. 2020;61(7):547.
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© ARVO (1962-2015); The Authors (2016-present)
It has previously been found that people with low vision and older adults have higher tolerance to defocus than normally sighted young adults. Some studies have also shown that myopes have higher blur detection thresholds than emmetropes, which may result in higher blur tolerance. This study was designed to determine if myopes, who have daily experience with blur, have higher blur tolerance than emmetropes in acuity tasks.
24 myopes and 25 age-matched emmetropes participated in this study. The mean prescription for the myopic group was -4.24 D with a range from -0.75 D to -10.75 D. Distance visual acuity charts, near visual acuity charts and MNREAD reading charts were used to test participants with two different viewing conditions: clear viewing and blurred viewing. In the clear viewing condition, participants were tested with their normal or corrected-to-normal vision. In the blurred viewing condition, participants wore goggles with diffusing films that reduced average distance acuity to 0.87 logMAR (SD: 0.07) . Blur tolerance was defined as the acuity measurements under the blurred viewing condition. We hypothesized that myopes would have higher blur tolerance (better acuity in blurred viewing conditions) than emmetropes because myopes have had more exposure to blur in their daily lives.
Table 1 summarizes mean acuities for clear and blur conditions and shows group differences. . In the clear viewing condition, the emmetropic group had better mean logMAR acuities than the myopic group as follows—distance visual acuity (-0.15 vs. -0.05, t(40.6) = 4.67, p < .001); near visual acuity (-0.17 vs -0.12, t(43.7) = 2.54, p < .05); and reading acuity (-0.21 vs -0.15, t(46.6) = 3.7, p < .001) . In the blurred viewing condition, the emmetropic group had better average reading acuity than the myopic group (0.81 logMAR vs 0.97 logMAR, t(24.71) = -3.66, p < .05). But there was no significant group difference in the other acuity measurements. In short, the myopic group did not demonstrate greater blur tolerance than the emmetropic group.
Although myopes have more experience of blur in their daily lives, our results indicate that they do not have superior acuity for blurred letters or text.
This is a 2020 ARVO Annual Meeting abstract.
Table 1. This table shows the means and SDs of three acuity measurements for the myopic and emmetropic group under two viewing conditions. The bottom row specifies if there were significant differences between the two groups.
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