The Safety And Efficacy Of Transepithelial Photorefractive Keratectomy Using Amaris 1050 Rs Excimer Laser In Extreme High Myopia(>-8 Diopter) : Results From A 6 Months Follow-Up Study.

To investigate whether Trans-PRK in patients with extreme high myopia (>-8D) maintains efficacy and stability even after 6 months of follow up study, and to analyze the factors affecting the efficacy and stability.

Corneal epithelial thickness was measured at the center near the visual axis using CIRRUS™ HD-OCT 5000. Since the epithelial thickening in the para-periphery of cornea was not reflected, We classified into 3 groups(central, moderate, para-central) according to the epithelial thickening pattern. Visual acuity and refractive changes were analyzed for each group. Real ablation amount was calculated the difference between only corneal stroma thickness except corneal epithelial thickness.

Trans-PRK was performed using Amaris 1050RS for 80 eyes with extreme high myopia(-8 diopter or more) with/without astigmatism. Corrected distance visual acuity(CDVA), Uncorrected visual acuity(UCVA), myopia, astigmatism and spherical equivalent(SE) were measured at postoperative 1 week, 1 month, 3 months and 6 months. The planned ablation amount & zone were compared with the real ablation amount & effective ablation zone. Corneal thickness and epithelial thickness were measured before and 6 months after surgery.

The UCVA(logMAR) was 0.07±0.09(1week) 0.03±0.05(1month), 0.02±0.04(3months) and 0.01±0.03(6months), which improved over time. The SE(D) ​​were -0.24±0.64(1week), -0.22±0.57(1month), -0.25±0.69(3months), and -0.50±-0.66(6months), which decreased at 1 month and then increased again. The epithelial thickness before and after surgery significantly increased from 48.28±2.85μm to 52.78±7.5μm (p<0.001). Factors affecting the SE at 6 months after surgery were analyzed by multiple regression analysis, and it was correlated with the increased amount of epithelium(p<0.001). The myopic shift was more severe when the center of the epithelium was thickened (24 cases, 30.4%) than when the paracentral region was thickened (37 cases, 46.8%) (p < 0.001)

Trans-PRK surgery showed good results in efficacy and safety even in long-term follow-up in patients with extreme high myopia of -8 diopters or more. There was a myopic tendency to spherical equivalent after surgery, but there was no decreased visual acuity. Therefore, it seems more likely that the myopic shift due to the thickening of epithelial cells is the cause rather than regression.