Comparative Refractive and Vector Outcomes of PRK in Moderate and High Astigmatism: A 12-Month Retrospective Study

To evaluate the photorefractive keratectomy (PRK) results in patients with moderate to high astigmatism.

One hundred twelve eyes of 71 patients with a cylindrical component of greater than 3 diopters (D) (moderate: 3.00 to 3.99 D; high: ≥4.00 D) undergone PRK were reviewed. UDVA, CDVA, and subjective refraction before and after surgery (1, 3, 6, 12 months) were extracted.

The preoperative mean spherical equivalent (SE) was -3.39 ± 1.82 D (range -9.00 to 2.50 D), and the mean cylinder was -3.76 ± 0.78 D (range -3.00 to -6.00 D). The mean postoperative cylinder values were -0.73 ± 0.49 D, -0.72 ± 0.46 D, -0.58 ± 0.48 D, and -0.4 ± 0.63 D at 1- month, 3-month, 6-month, and 12-month visits, respectively. The final follow-up efficacy and safety indices were 0.92 ± 0.14 and 0.99 ± 0.10, respectively. The postoperative residual astigmatism was 0.5 D or less in 50% of the eyes, and 75.9% of eyes were within ±0.50 D of the target spherical equivalent. In multivariable GEE analysis, higher preoperative cylinder (P = 0.005) and poorer preoperative CDVA (P = 0.002) were significant independent predictors of higher residual astigmatism. Longer Mitomycin C (MMC) application time was also associated with higher residual astigmatism (β = 0.006 D/s, P = 0.033), which likely reflects confounding by indication. The target induced astigmatism vector (TIA), surgically induced astigmatism vector (SIA), and difference vector (DV) were significantly higher in the high astigmatism group at final follow-up (p < 0.001). The angle of error was ±5 degrees in 71% and ±15 degrees in 100% of the eyes.

PRK is an effective and predictable method for the correction of moderate to high astigmatism.