Abstract:

BACKGROUND: The optimum ethanol exposure time to ensure the viability of corneal epithelial flap is the research hotspot for laser subepithelial keratomileusis.
OBJECTIVE: To investigate the factors influencing the viability of corneal epithelial flap in laser subepithelial keratomileusis (LASEK). 
METHODS: A standard LASEK was performed on 100 eyes of 50 myopic patients prospectively. The preoperative spherical equivalent ranged from -1.37 m^-1 to -6.00 m^-1, with the mean value of (-4.09 m^-1±2.12 m^-1). Eyes were divided to two groups, low myopic group A (<-3.00 m^-1, 40 eyes) and moderate myopic group B (-3.00 m^-1-6.00 m^-1, 60 eyes). All of the eyes were exposed to 20% ethanol for 15 and 25 seconds, so group A was divided to group A1(15 seconds) and group A2 (25 seconds) (20 eyes for each group), and group B was divided to group B1 (15 seconds) and group B2 (25 seconds) (30 eyes for each group). Uncorrected visual acuity (UCVA) and corneal fluorescein staining and corneal haze were noticed and compared at the 12 months of follow-up.
RESULTS AND CONCLUSION: The healing time of epithelium of group A1 was significantly longer than that of group A2, and the healing time of epithelium of group B1 was significantly longer than that of group B2 (P < 0.01). In terms of Haze grade 2, there was significant difference between group A1 and group A2 (P < 0.05) and between group B1 and group B2 (P < 0.01). Score of corneal fluorescein staining was positively correlated with Haze frequency. Under corresponding cutting depth of corneal matrix in LASEK, we obtained high quality and fine viability of corneal epithelial lap if we shortened the ethanol expose time, so we were satisfied with the healing time of cornea and vision and decreased frequency of Haze. These findings suggest that in the LASEK, under proper cutting depth of corneal matrix, shorter ethanol expose time leads to better quality of corneal epithelial flap prepared, better flap viability, and faster healing, which contribute to recovery of vision.