Evaluation of the effect of optic zone diameter selection on high-order aberrations in photorefractive keratectomy excimer laser treatment

Abstract

To evaluate the postoperative higher-order aberration (HOA) differences and visual quality outcomes of wavefront-optimised photorefractive keratectomy (PRK) surgery in 6.5-mm and 7.0-mm optic zones. The study included 136 eyes of 68 patients who underwent wavefront-optimised PRK surgery for myopia or myopia with astigmatism. Q values, third-order coma (Z [3, 1] and Z [3, − 1]), third-order trefoil (Z [3] and Z [3, − 3]), fourth-order spherical aberration (Z [4, 0]) and aberration coefficients were evaluated before surgery and 6 months after surgery. All patients underwent ophthalmic examinations that included visual acuity, central corneal thickness and intraocular pressure. The mean age of participants was 25.5 ± 6.7 (18–50 years). A total of 38 (55.88%) participants were male and 30 (44.12%) were female. In half of the eyes (n = 68), the 6.5-mm optic zone was selected (group 1), while the 7.0-mm optic zone was selected for other half (n = 68; group 2). No statistically significant difference was observed between the two groups in terms of preoperative best corrected visual acuity (BCVA) and postoperative uncorrected visual acuity (UCVA) (p = 0.45 and p = 0.22, respectively). The 7.0-mm optical zone was found to be associated with lower aberration coefficient values and lower Z [4, 0] spherical aberrations of HOAs. Although the 6.5-mm optical zone was associated with an increase in most wavefront aberration variables, measurements were not statistically different between two groups other than aberration coefficients and Z [4, 0] spherical aberrations. Photorefractive keratectomy performed with both the 6.5-mm and 7.0-mm optical zone diameters is very successful in correcting refractive errors. For some HOAs, treatment with the 7.0-mm optical zone seems to be more advantageous.