[Influence of Different Ablation Frequencies on the Clinical Results of Photorefractive Keratectomy Using the Same...

Background The objective of this study was to evaluate postoperative clinical outcomes of photorefractive keratectomy (PRK) using different ablation frequencies. Patients and Methods In this prospective, contralateral eye study, 56 eyes of 28 patients with myopia or myopic astigmatism were included. PRK was performed using the MEL90 excimer laser system (Carl Zeiss Meditec, Germany). One eye of each patient was treated with a repetition rate of 250 Hz, while the other one was treated with a repetition rate of 500 Hz. The treatment pattern in the 250 Hz and 500 Hz group only differed in terms of ablation frequency; there was no difference in laser pulse energy, spot size or ablation profile. Postoperative follow-ups were at 3 and 7 days and 1, 3 and 6 months. The following parameters were assessed: Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), higher-order aberrations (HOAs), corneal re-epithelisation time and corneal haze. Results Ablation depth was proportional to laser pulse counts at both frequencies. At 6 months, 100.0% of the eyes in the 250 Hz group and 96.4% in the 500 Hz group had a UDVA of 0.00 logMAR or better; 100% of the eyes in both groups were within ± 1.00D of the attempted correction. All eyes had a postoperative CDVA of 0.00 logMAR or better. There was no difference between the groups in postoperative HOAs, corneal re-epithelisation time or corneal haze. Conclusions Photorefractive keratectomy with a repetition rate of 250 Hz and 500 Hz showed comparable efficacy, safety and predictability in the correction of myopia. There were no significant complications due to the high repetition rate, such as postsurgical corneal haze.