Two-year stability of posterior corneal surface after transepithelial photorefractive keratectomy with a residual stromal thickness less than 350 μm

Abstract

Purpose: This study aimed to investigate the stability of posterior corneal surface 2 years after transepithelial photorefractive keratectomy (TPRK) in patients with a residual stromal thickness less than 350 μm.

Methods: In total, 408 eyes of 212 patients (160 women, 52 men) who underwent TPRK were enrolled in this retrospective study. All surgeries were performed in the Amaris 750S excimer laser platform with smart pulse technology. The posterior corneal elevation, anterior chamber depth, Q value, and curvature were measured using Pentacam preoperatively and postoperatively. All patients were followed up for 2 years. The relationship between percent tissue altered (PTA), age, and changes in posterior corneal surface was analyzed.

Results: The mean preoperative spherical equivalent was - 6.80 ± 1.18 D (range: - 9.00 to - 2.63 D). The mean residual stromal thickness was 336.46 ± 7.25 μm (range: 310-348 μm). The mean PTA was 30.93 ± 2.03% (range: 24.29-35.28%). At 2 years after surgery, the elevation of six points in the central area decreased by 1.91 ± 2.97 μm, 2.98 ± 3.23 μm, 1.17 ± 3.85 μm, 1.70 ± 2.88 μm, 1.36 ± 3.19 μm, and 1.65 ± 3.18 μm, compared with the preoperative value (P < 0.05). The elevation of three points in the peripheral area increased by 1.87 ± 6.34 μm, 0.68 ± 6.00 μm, and 0.95 ± 5.50 μm (P < 0.05). There was no significant linear relationship between PTA, age, and changes in posterior corneal surface, anterior chamber depth, and K2 (all P > 0.05).

Conclusion: Within 2 years after TPRK, the posterior corneal surface remained stable in patients with a residual stromal thickness between 310 and 350 μm. There was no sign of iatrogenic ectasia during the follow-up period.

Keywords: Percent tissue altered; Posterior surface of cornea; Residual stromal thickness; TPRK.