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We read with interest the excellent article by Shah et al.  The authors compared the outcomes of epithelial debridement for photorefractive keratectomy (PRK) with those of epithelial flap for PRK. They used 20% ethanol for 30 seconds and 45 seconds for the debridement and flap techniques, respectively. They observed that epithelial flap resulted in faster visual rehabilitation and reduced haze. We have ob...
We read with interest the excellent article by Shah et al.  The authors compared the outcomes of epithelial debridement for photorefractive keratectomy (PRK) with those of epithelial flap for PRK. They used 20% ethanol for 30 seconds and 45 seconds for the debridement and flap techniques, respectively. They observed that epithelial flap resulted in faster visual rehabilitation and reduced haze. We have observed that laser subepithelial keratomileusis (LASEK), using hinged epithelial flap reduced the incidence of postoperative pain and of corneal haze as compared to PRK.[2,4]
In the study by Shah et al1 20% dilute alcohol was applied for 45 seconds for epithelial flap-treated eyes. The duration of exposure may have facilitated epithelial flap removal in this study. Gabler et al  have reported that the vitality of corneal epithelial cells was reduced when exposure to 20% alcohol exceeded 45 seconds. We employed the same alcohol concentration to treat our patients using a similar surgical LASEK technique4 as well as using the Camellin LASEK technique. However, we used a shorter duration 20 to 30 seconds and we did not encounter any difficulty in the creation of LASEK epithelial flaps. It was our impression that decreased exposure to alcohol would result in increased epithelial flap viability, which may be associated with less postoperative pain and tearing. We have had limited experience of applying the same alcohol concentration for 45 seconds in LASEK procedure, which allowed greater ease of lifting of the epithelial flap without tears or buttonholes, but the flap did not seem to have good adherence. The data reported by Shah et al1 suggests that our assumptions regarding the need for reduced exposure times to alcohol may have been wrong.
Based on the convincing data by Shah et al, we plan to modify our technique and increase the duration of alcohol to 45 seconds. Before changing our technique, however, we would appreciate any caveats regarding the authors' technique, which may minimize potential problems.
We have used a therapeutic contact lens in the first 3-4 days after surgery. In the study by Shah et al1 PRK was performed in one eye and epithelial hinge flap procedure in the other eye, without using a contact lens. Our patients received therapeutic soft contact lenses after surgery to minimize postoperative pain. In the discussion of their results, Shah et al1 have indicated that they have started using contact lenses in subsequent patient treatments. We would appreciate the authors' recommendations regarding optimal alcohol exposure in setup of contact lens use and their experience with the effect of contact lens use on pain reduction after 45 seconds of alcohol exposure.
Jae Bum Lee
Dimitri T. Azar
Department of Ophthalmology
Massachusetts Eye and Ear Infirmary
(1) Shah S, Saran ARS, Doyle SJ, et al. The epithelial flap for photorefractive keratectomy. Br J Ophthalmol 2001;85;393-6.
(2) Lee JB, Seong GJ, Lee JH, et al. Comparison of laser epithelial keratomileusis and photorefractive keratectomy for low to moderate myopia. J Cataract Refract Surg 2001;27:565-70.
(3) Gabler B, Mohrenfels WV, Lohmann CP. Laser epithelial keratomileusis (LASEK): A histological study to investigate the vitality of corneal cells after alcohol exposure. Invest Ophthalmol Vis Sci 2001;42;S600.
(4) Azar DT, Ang RT, Lee JB, et al. Laser subepithelial keratomileusis (LASEK): Electron microscopy and visual outcomes of flap PRK. Curr Opin Ophthalmol 2001 Aug; in press.