Purpose: To evaluate various methods of surface ablation by comparing the integrity of basal epithelial cells and the basement membrane using transmission electron microscopy.
Methods: Corneal epithelial flaps were created using four approaches: mechanical removal (using a blunt spatula after application of 0.5% proparacaine, mechanical group); conventional LASEK (after application of 20% alcohol for 20 seconds, LASEK group); epi-LASIK using PMMA separator (PMMA separator group); or epi-LASIK using metal separator (metal separator group). Each group comprised epithelial sheets taken from five eyes of five patients. The sheets were immediately fixed in glutaraldehyde following removal. The flaps were examined using both light and transmission electron microscopy by three independent observers blinded to the creation methods, who assessed the adherence and integrity of the basement membrane to the basal epithelial layer.
Results: In the mechanical and PMMA separator groups, > 70% of flap areas had an intact basement membrane and normal basal cell integrity. Such integrity was present in < 30% of the flap areas in the LASEK group, and in 30% to 70% of the flap areas in the metal separator group. Different epikeratomes caused different amounts of damage.
Conclusions: Mechanical scraping and epi-LASIK were superior to LASEK in terms of preservation of the epithelial basement membrane and basal epithelial cells. Preservation ratio may differ depending on the type of epikeratome used.