A Randomized Trial to Evaluate the Effect of Toric Versus Spherical Contact Lenses on Vision and Eyestrain.

Objectives: To compare the effect of toric versus spherical soft contact lenses on objective measures of visual performance using visual acuity and electromyography of the orbicularis oculi muscle. Methods: Current soft contact lens wearers with -0.75 to -1.75 D astigmatism in each eye were binocularly fitted with toric (1-Day ACUVUE MOIST for astigmatism) and spherical (1-Day ACUVUE MOIST) contact lenses in random order. After each fitting and at 1-week follow-up, high- and low-contrast visual acuities were measured. Electromyography was used to objectively evaluate eyestrain. Linear mixed models were used to assess differences between toric and spherical contact lenses. Results: The mean age (+/- SD) of the 60 participants was 27.5 +/- 5.0 years, spherical refractive error was -3.68 +/- 2.01 D, and cylinder was -1.28 +/- 0.36 D. High- and low-contrast visual acuities with toric lenses were better than with spherical lenses at both fitting (toric high-contrast: -0.065 +/- 0.078 and low-contrast: 0.133 +/- 0.103 vs. spherical high-contrast: 0.001 +/- 0.104 and low-contrast: 0.224 +/- 0.107) and follow-up (toric high-contrast: -0.083 +/- 0.087 and low-contrast: 0.108 +/- 0.107 vs. spherical high-contrast: -0.015 +/- 0.095 and low-contrast: 0.211 +/- 0.104) (all P<0.0001). Electromyography-measured eyestrain was less with toric versus spherical contact lenses at fitting (least-square ratio of toric over spherical=0.72; P=0.0019) but not at follow-up (ratio=0.86; P=0.11). Conclusion: These results suggest that toric contact lenses provided improved objective measures of vision in a low-to-moderate astigmatic population.