PURPOSE: To study the effects of extended contact lens wear (EW) on the movement of basal epithelial cells toward the corneal surface. METHODS: Rabbits (n = 32) were injected with 5-bromo-2-deoxyuridine (BrdU) to label a group of proliferating basal epithelial cells, and, 24 hours later, one randomly chosen eye was fitted with a low- or medium-oxygen-transmissible (Dk/t) rigid gas permeable (RGP) contact lens, while the other eye served as the control (n = 28). Four rabbits were not fitted with any contact lens. Rabbits were euthanatized at different time points and the corneal epithelium was immunocytochemically stained for BrdU and/or Ki-67 and counterstained with propidium iodide or Syto 59. Corneal flatmount tissues were examined three dimensionally under a laser confocal microscope and the location of each BrdU-labeled cell in the corneal epithelium (basal or suprabasal) was determined. RESULTS: Four days after injection of BrdU, both low- (P < 0.001) and medium-Dk/t RGP (P < 0.001) lens groups showed significantly more BrdU-labeled cells in the basal cell layer than in the control eyes. Six days after injection of BrdU, a small percentage of BrdU-labeled cells (<0.5%) were Ki-67 positive. CONCLUSIONS: Within 6 days, the majority (80%) of BrdU-labeled basal cells became terminally differentiated and rarely divided secondarily in the central epithelium. Short-term use of low- and medium-Dk/t RGP EW contact lenses slows the normal movement of basal epithelial cells toward the surface in the central cornea. This is consistent with known EW-lens-induced decreases in corneal epithelial basal cell proliferation and surface cell exfoliation. Overall, the data suggest that EW lenses significantly inhibit the normal homeostatic turnover rate of the corneal epithelium.
PURPOSE: To study the effects of extended contact lens wear (EW) on the movement of basal epithelial cells toward the corneal surface. METHODS:Rabbits (n = 32) were injected with 5-bromo-2-deoxyuridine (BrdU) to label a group of proliferating basal epithelial cells, and, 24 hours later, one randomly chosen eye was fitted with a low- or medium-oxygen-transmissible (Dk/t) rigid gas permeable (RGP) contact lens, while the other eye served as the control (n = 28). Four rabbits were not fitted with any contact lens. Rabbits were euthanatized at different time points and the corneal epithelium was immunocytochemically stained for BrdU and/or Ki-67 and counterstained with propidium iodide or Syto 59. Corneal flatmount tissues were examined three dimensionally under a laser confocal microscope and the location of each BrdU-labeled cell in the corneal epithelium (basal or suprabasal) was determined. RESULTS: Four days after injection of BrdU, both low- (P < 0.001) and medium-Dk/t RGP (P < 0.001) lens groups showed significantly more BrdU-labeled cells in the basal cell layer than in the control eyes. Six days after injection of BrdU, a small percentage of BrdU-labeled cells (<0.5%) were Ki-67 positive. CONCLUSIONS: Within 6 days, the majority (80%) of BrdU-labeled basal cells became terminally differentiated and rarely divided secondarily in the central epithelium. Short-term use of low- and medium-Dk/t RGP EW contact lenses slows the normal movement of basal epithelial cells toward the surface in the central cornea. This is consistent with known EW-lens-induced decreases in corneal epithelial basal cell proliferation and surface cell exfoliation. Overall, the data suggest that EW lenses significantly inhibit the normal homeostatic turnover rate of the corneal epithelium.