ABSTRACT
PURPOSE: To assess the visual performance of Acuvue bifocal contact lenses at different illumination levels using a stereoscopic parameter, the maximum disparity. We compare the results with those for progressive spectacle lenses. METHODS: We used a modified Wheatstone stereoscope and random-dot stereograms (RDS) as tests. The maximum disparity was measured for each observer at different luminance levels. RESULTS: Maximum disparities did not show statistically significant differences for a wide range of luminance levels with contact lenses. The maximum disparities found when some contact-lens users wore progressive spectacle lenses were similar. CONCLUSIONS: The results show that the Acuvue bifocal lenses offer good performance for a near visual task, in this case the maximum disparity, for changes in illumination and are similar to that with progressive spectacle lenses.
Subject(s)
Contact Lenses , Depth Perception , Lighting , Photic Stimulation/methods , Adult , Distance Perception , Equipment Design , Eyeglasses , Humans , Middle Aged , Optics and PhotonicsABSTRACT
We offer an analysis that shows that the approximations made for the ablation depth during practical refractive surgery, in which the square-root terms are replaced by the first two terms of the series expansion, can limit the visual function of the observer by reducing the modulation transfer function (MTF). To simulate the refractive-surgical operation, we considered two groups of myopic patients with different ametropia who were emmetropized with different ablation profiles. We made the MTF calculations by taking the spherical aberration into account. In addition, a fuller analysis showed that these approximations limit the possibility of considering surfaces that are aspherical for reshaping the anterior cornea to optimize the observer's visual function.
