Epi–LASIK Is Not Equal to Alcohol–Free LASEK

Abstract

Abstract: : Purpose: To analyze the difference in the histological ultrastructure of human corneal epithelial flap by Epi–LASIK and LASEK. Methods: 6 eyes of 6 patients and 4 eyes in vitro were included in this study. Epithelial flap was obtained by Epi–LASIK method using rotational epikeratome (Made in China) in 3 eyes of 3 patients and 2 eyes in vitro. And epithelial flap was created by LASEK technique in the other 5 eyes using 20% alcohol for 20 seconds. All specimens were assessed by light and electron microscopy, and the histological difference of the two methods was compared. Results: Epithelial flaps were created smoothly in all the 5 eyes of mechanical method and in 4 eyes of alcohol–assisted method. Epithelial flap was not intact in 1 eye. Light microscopic examination showed most of the basal border of the Epi–LASIK epithelial flap was continuous with occasional focal disruptions. There was no evident morphological abnormalities. The alcohol–assisted epithelial flap had significant interruption along the basal border of the epithelium. Bowman’s membrane and anterior stroma remained completely intact in any specimen for both methods. Transmission electron microscopy showed that most of the basement membrane of the mechanical epithelial flap was integrity. The lamina densa, lamina lucida and the hemidesmosomes had normal morphology along most of basement membrane. The basal cell showed normal ultrastructure. Most of the basement membrane was abnormal in specimens obtained with alcohol–assisted separation. Most lamina densa was absent and lamina lucida was interruption. The mitochondrion of basal cell was swelling and crista was disruption. And part of basal cell membrane was damaged. Conclusions: The cleavage plane of mechanically separated epithelial flap was underneath the basement membrane. Most of the basement membrane was integrity and cell morphology was normal. The cleavage plane of alcohol–assisted method was mostly between basal cell membrane and basement membrane. Basement membrane and the basal cell morphology were abnormal.

Keywords: refractive surgery: comparative studies • cornea: epithelium