Comparison of the topographic ablation zone after photorefractive keratectomy for myopia using two different excimer lasers

Purpose To compare the topographic features of eyes treated with photorefractive keratectomy (PRK) for myopia using two different excimer lasers. Methods A total of 65 eyes in 39 patients treated with PRK (6.0-mm optical zone) using Technolas 217C and VISX S4 excimer lasers were evaluated retrospectively to determine the size of the topographic ablation zone. Results The zones ablated using the VISX S4 had shorter diameters in both axes (-0.89 +/- 0.73, -1.59 +/- 0.49 mm; both P = 0.00), whereas those ablated using the Technolas 217C had a longer diameter in the major axis (0.96 +/- 0.63 mm; P = 0.00) and a shorter diameter in the minor axis (-0.39 +/- 0.59 mm; P = 0.00). The theoretical ablated zone was a circle with a diameter of 6.0 mm. The Technolas 217C group tended to have oval cuts in comparison with the VISX S4 group, and the difference between the programmed (6.0 mm) and topographic diameters was significant in both groups. Conclusions There was a difference between the programmed and postoperative topographic diameters of the ablation zone. The postoperative ablation zone differed in shape and size according to the type of excimer laser. Eye (2010) 24, 553-557; doi:10.1038/eye.2009.169; published online 24 July 2009