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.

Demonstrating correction of low levels of astigmatism with realistic scenes.

PURPOSE AND METHOD: Modern standard visual acuity tests are primarily designed as diagnostic tools for use during subjective refraction and normally bear little relation to real-world situations. We have developed a methodology to create realistic rendered scenes that demonstrate potential vision improvement in a relevant and engaging way. Low-cylindrical refractive error can be made more noticeable by optimizing the contrast and spatial frequencies, and by testing four different visual perception skills: motion tracking, pattern recognition, visual clutter differentiation and contrast sensitivity. Using a 1.00DC lens during iteration, we created a range of still and video scenes before optimizing to a selection 3-D rendered street scenes. These were assessed on everyday relevance, emotional and visual engagement and sensitivity to refractive correction for low-cylinder astigmats (0.75-1.00DC, n=74) wearing best spherical equivalent correction and then with astigmatism corrected. RESULTS AND CONCLUSIONS: The most promising visual elements involved or combined optimized textures, distracting patterns behind text, faces at a distance, and oblique text. 91.9% of subjects (95% CI: 83.2, 97.0) reported an overall visual improvement when viewing the images with astigmatic correction, and 96% found the images helpful to determine which type of contact lens to use. Our method, which combines visual science with design thinking, takes a new approach to creating vision tests. The resultant test scenes can be used to improve patient interaction and help low cylinder astigmats see relevant, every-day benefits in correcting low levels (0.75 & 1.00DC) of astigmatism.