Comparison of postoperative higher-order aberrations and contrast sensitivity: Tissue-saving versus conventional photorefractive keratectomy for low to moderate myopia
PURPOSE: To assess the efficacy, predictability, safety, contrast sensitivity, higher-order aberrations (HOAs), and patient satisfaction after tissue-saving photorefractive keratectomy (PRK) and conventional PRK. SETTING: Department of Ophthalmology, Farabi Eye Hospital, Tehran Medical University, Tehran, Iran DESIGN: Comparative case series. METHODS: This prospective study evaluated eyes with low to moderate myopia that had PRK with a Technolas 217z excimer laser. Patients were randomly assigned to have surgery using a conventional algorithm (PlanoScan) or a tissue-saving algorithm (Zyoptix). Contrast sensitivity, HOAs, and patient satisfaction were analyzed preoperatively and 1, 3, and 6 months postoperatively. RESULTS: The conventional group comprised 42 eyes (21 patients) and the tissue-saving group, 62 eyes (31 patients). At 6 months, all eyes in both groups were within +/- 0.50 diopter of the attempted correction and had an uncorrected distance visual acuity of 20/25 or better. However, the tissue-saving group had a statistically significantly greater increase in the mean root mean square of total HOAs and more induced spherical aberration than the conventional group (P<.05). There was no significant difference between the 2 groups in mesopic or photopic contrast sensitivity. The level of satisfaction after surgery was the same in the 2 groups. CONCLUSIONS: Although the conventional and tissue-saving algorithms for PRK were both safe and effective in treating low to moderate myopia, tissue-saving PRK induced a greater increase in HOAs than conventional PRK; this may be because of the smaller blend zone of the tissue-saving algorithm. Contrast sensitivity and patient satisfaction were comparable between the 2 methods.