[The clinical study of corneal cross-linking with preserved corneal epithelial flap in thin keratoconic corneas].

Objective: To evaluate the therapeutic effect of corneal collagen cross-linking (CXL) with preserved corneal epithelial flap and isotonic riboflavin for treatment of keratoconus eyes with thin corneas. Methods: Prospective case-control study. Twenty two eyes of 20 patients (16 males and 4 females, with age of 23.5±4.9), who have been diagnosed with progressive keratoeonus and the comeal stroma thickness of whom were less than 400μm (without the epithelium), were included in this study. Corneal collagen crosslinking was performed under preserved corneal epithelial flap (8.5mm), followed by instillation of 0.1% riboflavin and then UV irradiation. The corneal epithelial flap must be restored prior to the application of UVA irradiation. Visual acuity, corneal topography and endothelial cell count were evaluated at baseline and at 12 months follow-up. Data were analyzed using paired samples t test. Results: Corneal topography results of 12m before and after the therapy revealed the significant reductions of Kmax from (54.73±4.39)D to (53.46±3.85)D and Kmin from (48.97±3.72)D to (48.41±3.17)D, and also Km from (51.67±3.77) D to (50.77±3.28) D (Kmax: t=- 3.138, P< 0.05; Kmin: t=- 2.170, P< 0.05; Km: t=- 3.532, P< 0.05). No statistically significant differences were found between the average corneal thickness of pre therapy [(400.6±14.9) μm] and post therapy [(396.5±16.3)μm] ( t= 1.973, P> 0.05). Endothelial cell counts of pre therapy [(2 824±308)/mm(2)] and post therapy [(2 753±372)/mm(2)] were of no statistical significance as well ( t= 0.928, P> 0.05). No complications such as scarring lesions in the stroma and corneal endothelial damage were observed throughout the study period. Most of the patient's vision improved after treatment. Conclusion: The application of isotonic ribonavin solution in a cross-linking procedure in thin corneas with preserved corneal epithelial flap seems to be safe and effective as keratoconus tend to be stable at 12 months after therapy and no endothelial cell damage was caused. (Chin J Ophthalmol, 2018, 54: 421 - 425) .