Sections were examined by fluorescence microscopy (model BX51; Olympus Co., Tokyo, Japan) and by an inverted microscope (Leica Microsystems GmbH, Wetzlar, Germany) at a magnification of 100× to 400×. The images were obtained with one of two cameras (VDS CCD-1300QF; VDS Vosskühler GmbH, Osnabrück, Germany, or Jenoptik ProgRes C12plus; Jenoptik; Laser.Optik.Systeme GmbH, Jena, Germany) and produced with image-management software (NIS Elements; Laboratory Imaging, Prague, Czech Republic). At least 300 cells of the central corneal, limbal, and perilimbal conjunctival epithelium were examined, and the percentage of positive cells was calculated. The following scale was used to grade the intensity of cell staining: N, negative; 1, weak; 2, moderate; 3, intense; and 4, very intense. The mean range was calculated from three sections and two experiments.