Laserepitheliale keratomileusis (LASEK): Histologische untersuchungen zur vitalität der kornealen epithelzellen nach alkoholexposition

Background: Laser epithelial keratomileusis (LASEK) is a new surgical procedure to treat myopia. An epithelial flap is created after the exposure to 20% alcohol and following the laser ablation the epithelium is repositioned to its original location. The advantage of LASEK is that the ablated corneal surface is covered by a full thickness epithelium immediately after surgery. It is hypothesised that this epithelial coverage inhibits the wound healing response of the cornea. However, this concept will only work if the epithelial cells are still vital after the exposure to alcohol. Material and methods: The vitality of the corneal epithelial cells was investigated in 6 human cadaver eyes after the exposure to 20% alcohol over 15 to 60 s. The vitality of the corneal epithelial cells was assessed by soaking the specimen in a 0.1% trypan blue solution and incubated at 37°C for 2 min. After a wash with BSS the specimen were re-incubated at 37°C for 30 min in culture medium. After one more wash with BSS the cells were observed with a standard light microscope. Cells which retained the blue colour would be dead and vital cells would appear clear. Light microscopy and transmission electron microscopy was used to detect morphological changes. Results: Mainly vital corneal epithelial cells were seen for an alcohol exposure time of up to 30 s. In particular the basal epithelial cells appeared alive. With a exposition time of 60 s most cells were dead. Conclusion: In LASEK the exposure time of 20% alcohol is between 20 and 30 s. Based on our results we can conclude that after such exposure time most cells are alive, which is essential for the postoperative wound healing response.