Effect of uncorrected astigmatism on vision.

PURPOSE: To examine the effect of uncorrected astigmatism in older adults.
SETTING: University vision clinic.
DESIGN: Investigational simulation.
METHODS: Healthy adult presbyopes had astigmatism of 0.00 to -4.00 diopters cylinder (DC) × 90 degrees and -3.00 DC × 90, × 180, and × 45 degrees induced with spectacle lenses, with the mean spherical equivalent compensated to plano, in random order. Visual acuity was assessed binocularly using a computerized test chart at 95%, 50%, and 10% contrast. Near acuity and reading speed were measured using standardized reading texts. Light scatter was quantified with a C-Quant straylight meter and driving reaction times with a computer simulator. Visual clarity of a mobile phone and computer screen was subjectively rated.
RESULTS: Distance visual acuity in the 21 volunteers decreased with increasing uncorrected astigmatic power (F = 174.50, P < .001) and at lower contrasts (F = 170.77, P < .001). Near visual acuity and reading speed also decreased with increasing uncorrected astigmatism power (P < .001). Light scatter was not significantly affected by uncorrected astigmatism (P > .05); however, the reliability and variability of measurements decreased with increasing uncorrected astigmatic power (P < .05). Driving simulator performance was unaffected by uncorrected astigmatism (P > .05), although subjective rating of clarity decreased with increasing uncorrected astigmatic power (P < .001). Uncorrected astigmatism at the 45-degree or 180-degree orientation resulted in worse distance and near visual acuity and subjective-rated clarity than at the 90-degree orientation (P < .05).
CONCLUSIONS: Uncorrected astigmatism, even as low as 1.00 D, caused significantly decreased vision and if left uncorrected could significantly affect patients' independence, quality of life, and well-being.