Experiments on PMMA models to predict the impact of corneal refractive surgery on corneal shape

Abstract

Flat and spherical PMMA surfaces were ablated with a standard refractive surgery laser system. The ratio of profiles on flat to spherical PMMA surfaces was used to estimate experimentally the radial change in ablation efficiency for PMMA and cornea. Changes in ablation efficiency accounted for most of the asphericity increase found clinically, using the same laser system. This protocol is useful to obtain a correction factor for any ablation algorithm and laser system, and to estimate the contribution of biomechanics to the increase of corneal asphericity in myopic refractive surgery.

Review of technological advancements in calibration systems for laser vision correction

“…28 This aspect is generally not considered while calibrating a laser system based on flat ablations performed on calibration materials. Dorronsoro et al 29 ablated flat and spherical PMMA surfaces with a standard refractive surgery laser system. They used the ratio of profiles on flat-to-spherical PMMA surfaces to estimate experimentally the radial change in ablation efficiency for PMMA and cornea.…”

Aspheric Refractive Correction of Irregular Astimatism

“…Biomechanical changes after Myopic Astigmatism treatments contribute to an oblate contour, increasing spherical aberration and shrinking the effective optical zone. Healing response 27 , radial ablation efficiency losses 28 and biomechanical effects 29 all reduce the effective ablation in the outer portion of the nominal optical zone. These effects shrink the actual zone of full refractive correction, i.e., the effective optical zone.…”

Treatment Strategies and Clinical Outcomes of Aspheric Surgery for Astigmatism Using the SCHWIND Amaris Platform

“…The CAM aspherical profiles were developed with the aim to compensate for the induction of aberrations (especially but not only spherical aberration) observed with other types of profile definitions 5 , some of these sources of aberrations are those related to the loss of efficiency of the laser ablation for non-normal incidence 6,7 . Optimization is realized by taking into account the loss of efficiency at the periphery of the cornea in relation to the center, as there is a tangential effect of the spot in relation to the corneal curvature (K (Keratometry) -reading).…”