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Impressum
Laser epithelial keratomileusis (LASEK): histological investigations for the vitality of corneal epithelial cells after alcohol exposure.
1,2Dreiss A. K., 3Winkler von Mohrenfels C. W., 3Gabler B., 2Kohnen T., 1Marshall J., 1,3Lohmann C. P.
1Dept of Ophthalmology, The Rayne Institute, ST Thomas' Hospital London; 2Zentrum für Augenheilkunde, Universität Frankfurt/Main; 3Universitäts-Augenklinik Regensburg
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 3 human cadaver eyes after the exposure to 20% alcohol
over 30 to 120 sec. The vitality of the corneal epithelial cells was assessed
by soaking the specimen in a 0.1% trypan blue solution and incubated at
37oC for 2 min. At this stage the all cells would have taken up trypan
blue and would appear blue. After a wash with BSS the specimen were reincubated
at 37oC 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 again
because of the ability to pump out the trypan blue.
Results: Vital corneal epithelial cells were seen up to an alcohol
exposure time of 45 sec. In particular the basal epithelial cells appeared
alive. Longer exposition times showed, that most cells were dead.
Conclusion: In LASEK the exposure time of 20% alcohol is between
20 and 30 sec. Based on our results we can conclude that after such exposure
time most cells are alive, which is the basis for inhibiting the postoperative
wound healing response.