Factors Influencing Cyclotorsion During Photorefractive Keratectomy.

PURPOSE To determine predictive factors for intra-operative cyclotorsion in photorefractive keratectomy (PRK). METHODS A retrospective statistical analysis of medical records pertaining to 3,996 eyes undergoing PRK was conducted. Outcome measures of this study were the likely existence of statistically significant relations between diverse and potentially influential factors and the occurrence of intraoperative cyclotorsion. RESULTS A total of 96% of examined medical records indicated some degree of cyclotorsion with the absolute mean intraoperative value of 1.38° ± 1.67° (range: 0° to 13.6°). Absolute mean cyclotorsion showed no significant correlation with age (r = 0.14, P = .37). Female patients had significantly higher degrees of cyclotorsion versus males (P < .001). Right and left eyes showed no significant difference in absolute mean torsion (P = .05). Higher diopters of refractive errors, hyperopia, more than 2.00 diopters of cylinder, high pulse numbers (r = 0.26), and use of the advanced personalized treatment ablation algorithm were all significantly related to higher degrees of torsion (P < .0001). Ablation depth (r = 0.13) and surgeon appeared to be dependent factors. CONCLUSIONS Incidence of intraoperative cyclotorsion is high in eyes undergoing PRK and most of them will experience some degree of torsion. Several diverse factors (sex, refractive error diopters, hyperopia, high cylinder, pulse numbers, and ablation algorithm) were significant predictors for higher degrees of the observed torsion. [J Refract Surg. 2018;34(2):106-112.].