Abstract
Abstract: :
Purpose: No prospective double-masked study has evaluated whether astigmatism truly benefits or harms the presbyopic patient, whose intermediate and near vision might theoretically benefit from low myopic astigmatism. This study is designed to compare visual function among patients thst were intentionally given either with-the-rule or against-the rule astigmatism using soft contact lenses to induce the astigmatism. DESIGN: Prospective, randomized, double-masked, crossover design. OUTCOMES: Binocular ETDRS LogMAR visual acuities at 3 distances: far (4m) intermediate (1m) and near (33cm). Near stereoacuity, using Randot Stereotest, and quality of life, using the Refractive Status and Vision profile, or RSVP, a standardized questionnaire were secondary outcomes. Method: 15 presbyopic patients aged 45 - 68 were recruited from an academic center population. These patients were given a baseline eye exam, including manifest refraction, ETDRS LogMAR visual acuity at distance, intermediate, and far, accommodative amplitudes, and stereo vision. Each patient was then cycled in random order through three masked pairs of soft contact lenses. The power of each contact lens pair was calculated by the subtraction method to maintain a spherical equivalent of -0.5 D, while providing either no astigmatism (spherical arm, SPH), 1 Diopter of WTR astigmatism, or 1 diopter of ATR astigmatism. Actual refractive errors produced were measured by masked examiner. Outcomes were measured at the end of one week of usage of each contact lens arm. Results: Visual Acuity results across the three arms were similar However, 1 meter visual acuity was better for the spherical arm than either astigmatic arm(-0.06 SPH, +0.01 WTR, +0.02 ATR). Near (33cm) and distance (4m) acuities were similar. Stereoacuity was better in the Against-the-Rule than With-the-rule arm (50 vs 102 sec, p= 0.01). Subjects preferred the Spherical Arm slightly over the WTR astigmatic arm by the RSVP quality of life survey instrument (101 vs 104, p =0.05). Other intergroup comparisons showed no difference in RSVP scores. Conclusion: This study has demonstrated that intermediate distance acuity and refractive quality of life is slightly better with spherical low myopic refractive error versus either astigmatic arm. Near and far distance acuity were unaffected by low myopic astigmatism compared to spherical low myopia. Near stereopsis was best in the ATR arms, but this did not produce better near visual acuity or RSVP quality of life.
Keywords: 325 astigmatism • 481 myopia • 367 contact lens