TransPRK in the treatment of low to moderate and high myopia: a comparative study of the clinical outcomes

The aim of this study is to compare the refractive parameters and visual quality of patients with low to moderate myopia and high myopia before and after transepithelial photorefractive keratectomy(transPRK)to evaluate the efficacy and safety of transPRK in correcting different degrees of myopia, and to explore the impact of the surgery on the visual quality of patients with different spherical equivalent(SER). This study retrospectively included myopic patients who underwent transPRK using the Schwind Amaris excimer laser. The patients were divided into the low to moderate and high myopia groups according to the preoperative spherical equivalent. The subjects' refractive parameters and visual quality before, at 1, 3, and 6 months after surgery were collected and analysed. The changes in each value before and after surgery (Δ) were compared. At 6 months after surgery, 96.8% (low to moderate myopia group) and 92.3% (high myopia group) of the eyes in both groups achieved uncorrected distance visual acuity (UDVA) of 20/20 or above. At 6 months after surgery, 65.1% of the eyes in the low to moderate myopia group had SER within ± 0.5D, and 95.2% had SER within ± 1.0D. In the high myopia group, 71.8% of the eyes had SER within ± 0.5D, and 97.4% had SER within ± 1.0D. No patient lost one or more lines of corrected distance visual acuity (CDVA) simultaneously after surgery. All patients achieved a CDVA of 20/20 after surgery. There were significant differences in △corneal higher-order aberrations at 6.0 mm pupil(C.HOA), △corneal spherical aberration at 6.0 mm pupil(C.Sph), and △corneal coma aberration at 6.0 mm pupil(C.Coma) between the two groups (P < 0.05). In comparison, there were no significant differences in △corneal trefoil aberration at 6.0 mm pupil(C.Tre), △and the strehl ratio(SR) between the two groups (P > 0.05). There were significant differences in △central corneal thickness (CCT), △anterior surface asphericity of the cornea (Q), △eccentricity (e) and △corneal curvature (K1, K2, and Km) between the two groups (P < 0.001). In the low to moderate myopia group, △SER was positively correlated with △C.HOA and △C.Sph (P < 0.01), and △SER was positively correlated with △C.Coma at 6 months (P < 0.01); there was no correlation between △SER and △C.Tre and △SR (P > 0.05). In the high myopia group, △SER was positively correlated with △C.HOA at 6 months (P < 0.05); △SER was positively correlated with △C.Sph and △SR at 3 and 6 months (P < 0.05). There was no correlation between △SER and △C.Coma or △C.Tre (P > 0.05). This study demonstrates that transPRK can safely and effectively correct the UDVA and refractive status of patients with low to moderate and high myopia. Compared with patients with low to moderate myopia, patients with high myopia have more increases in C.HOA, C.Sph, and C.Coma at the same time point after surgery.△SER is positively correlated with △C.HOA after surgery. Among the three aberrations, the correlation between △SER and △C.Sph is the strongest in the high myopia group simultaneously.