Regeneration of corneal nerve after SMILE, FS-LASIK and T-PRK surgery and study its relationship with subjective visual quality

Abstract

Objective: To explore nerve fiber regeneration and subjective visual quality of patients undergoing small incision lenticule extraction (SMILE) surgery, femtosecond laser-assisted in-situ keratomileusis (FS-LASIK) and transepithelial photorefractive keratectomy (T-PRK), and study their correlation. Methods: This is a prospective cohort study including 55 patients (6 male, 49 female, age 25.6±7.3, in total 109 eyes) who chose refractive surgery in Peking Union Medical College Hospital. They are subdivided into 3 groups: 35 patients in SMILE (4 male, 31 female), 9 patients in FS-LASIK (1 male, 8 female) and 11 patients in T-PRK (1 male, 10 female). All surgeries were conducted by the same surgeon. Patients underwent confocal microscopy examinations and filled in subjective visual quality questionnaires before surgery and 7 days, 30 days and 90 days after surgery. ACCMterics V.2 was used for nerve analysis. One-way analysis of variance, Kruskal-Wallis H test and Pearson correlation study was adopted for data analysis on SPSS 22.0. Results: Corneal nerve fiber density is lowest at 7 days after surgery. The nerve fiber length (8.53 (7.32), 9.33 (6.47), 10.98 (4.85) mm/mm(2), χ(2)=9.21, 8.15, 6.54; P<0.05), density (12.50 (12.50), 12.50 (12.50), 18.75 (14.06)/mm(2), χ(2)=6.54, 9.02, 7.01; P<0.05) and total branch density (18.75 (31.25), 24.99 (29.69), 31.25 (32.81)/mm(2), χ(2)=10.23, 7.63, 10.01; P<0.05) of SMILE group are significantly higher than the other 2 groups at 7 days, 30 days and 90 days after surgery. The subjective visual quality scores are (4.13±0.61), (3.54±0.71), (4.03±0.70) and (4.20±0.58) respectively at each visit, with 7 days being the lowest (F=1.51, P=0.23), but there is no statistically significant difference between each group at each visit. At 7 days after surgery, the nerve fiber length (CNFL) and nerve fiber density (CNBD) show strong positive correlation with overall subjective visual quality (r=0.378, 0.504; P<0.05), while there exists no significant correlation between nerve fiber parameters and subjective visual quality 30 days and 90 days after surgery. Conclusions: SMILE shows better results in corneal nerve fiber regeneration. Corneal nerve fiber density of early post-operational period is positively correlated with overall subjective visual quality. (Chin J Ophthalmol, 2018, 54: 737-743).