To investigate the long-term efficacy of transepithelial PRK in correction of low-moderate astigmatism using vector analysis.

In this follow-up study, 95 myopic eyes (up to 8 D) with astigmatism (up to 4 D) were included. The patients were recruited from Bina Eye Hospital, Tehran, Iran from August 2012 to December 2014. All of the cases underwent TransPRK by SCHWIND AMARIS 500 laser by the same expert surgeon. Patients were followed up to 18 months. Vector analysis according to Alpins method was used to analysis the correction of astigmatism. We also performed subanalysis in subgroups with different degrees of preoperative astigmatism as follows: ≤0.5D, 0.5-1 D, 1-2 D and 2-4 D

Patients had a mean age of 25.12±5.15 and 66.31% of eyes belonged to females. According to vector analysis, mean correction index (CI), index of success (IOS) and flattening index (FI) were 1.01±0.08, 0.03±0.12, 0.97±0.15, respectively. Mean magnitude of error (ME) was 0.00±0.11 D and mean angle of error (AE) was -2.21±18.32 degrees. Our subanalysis showed that the four subgroups (starting from ≤0.5D subgroup) achieved mean CIs of 1.01±0.09, 1.00±0.00, 1.08±0.12 and 0.99±0.05, respectively (P=0.6). IOSs calculated were 0.03±0.11, 0.00±0.00, 0.07±0.17 and 0.06±0.12, respectively (P=0.04). Accordingly, mean MEs were 0.00±0.04, 0.00±0.00, 0.03±0.20 and 0.04±0.15, respectively (P=0.57). Mean FIs were 0.97±0.13, 1.00±0.00, 0.94±0.22 and 0.92±0.18, respectively (P=0.15).

Efficacy of TransPRK in correction of astigmatism up to 4 D is almost optimal. This efficacy is more pronounced in reduction of astigmatism magnitude and there exists some slight error in the angle of treatment axis clockwise to the intended axis. Additionally, patients with low astigmatism achieved even better results compared to those with moderate astigmatism.