Purchase this article with an account.
Samuel Arba Mosquera, Shwetabh Verma; Optimum laser beam characteristics for achieving smoother ablations in laser based vision correction. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4866.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser based vision correction. We tested the impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap and lattice geometry on ablation smoothness, from both theoretically optimized super Gaussian beam profiles and physical intensity beam profiles acquired using a beam profiler camera.
Given the super Gaussian order, the theoretical beam profile was calculated and optimum truncation size was determined following Beer-Lambert model and using the metric ablation volume per laser pulse optimized for minimum pulse energy incident on a single spot (Biomed Opt Express. 2013 Jul 24;4(8):1422-33),. The physical intensity beam profile was acquired from an excimer laser using a beam profiler camera. For both the beam profiles, two geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlap distances and ablated material (cornea or PMMA). Real ablations on PMMA completed the study setup. Optimum global configurations were analyzed based on the minimum roughness in ablation estimated from the root mean square error in ablation.
Open based on the test cases. In general, there is an optimum peak radiant exposure for a given supergaussian order. The optimum truncation size corresponds to cutting off the flanks not contributing to the ablation process. Round spot geometries produce lower simulated roughness values than square ones. Triangular lattices produce lower simulated roughness values than reticular ones. Roughness on PMMA tend to be lower than on the cornea (but also ablation volume). Theoretical modelled beams produced lower simulated roughness values than the ones obtained with the beam profiler camera. Simulated roughness tends to be lower than measured roughness. Repetition rate affects the beam profile of the excimer laser. Simulated and measured results showed a good degree of correlation.
The proposed model can be used for optimization of laser systems used for ablation processes at relatively low cost and would directly improve the quality of results.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only