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Editor,—I read with great interest the paper by Thiel et al 1 who applied immunoperoxidase and immunofluorescence techniques to diagnose viral infections of the ocular surface. Eleven years ago, we described a method of immunocytological staining for viral antigens on ocular surface cells collected on cellulose acetate strips.2 Thiel and coworkers should be congratulated for improving this methodology by the use of a Biopore membrane device that facilitates specimen collection and processing. Another advantage common to these diagnostic techniques is that sample collection simultaneously accomplishes debridement, which may be beneficial in herpes keratitis and other viral infections of the ocular surface.
Editor,—We thank Dr Pepose for his comments on our improved impression cytology technique. He does point out the potential of this method for therapeutic debridement in superficial herpetic keratitis. As shown in Figures 3A and B of our recent article this technique does indeed allow a gentle and effective debridement of infected epithelial cells. It is also our experience that debridement by this method is beneficial for the healing process, and none of our patients followed so far developed complications after impression. The therapeutic effect of sample collection, however, was beyond the scope of this study and further investigations are required to clarify this aspect.