title: Recovery time of corneal epithelial proliferation in the rabbit following rigid gas-permeable extended contact-lens wear.
abstract: OBJECTIVE
  To determine recovery time needed for the corneal epithelium to return to a normal proliferation rate following 24-hour rigid gas-permeable (RGP) lens wear.
  
  
  METHODS
  An RGP lens (Dk/t = 10) was fitted at 9:00 am on one randomly chosen eye of each rabbit (N = 16) and removed 24 hours later while the other eye served as a control. Following contact lens removal, the rabbits were injected at four different time intervals (1,2, 4, and 7 days) with 5-bromo-deoxyuridine (BrdU) at 9:00 am to label dividing corneal epithelial cells. All animals were sacrificed 24 hours after BrdU injection, and corneas were stained for BrdU. A series of continuously adjacent digital images of the whole-mount epithelium was collected from superior limbus to central cornea, and all BrdU-labeled epithelial cell pairs on each digitized image were counted.
  
  
  RESULTS
  On day 1 following lens removal, the number of BrdU-labeled corneal epithelium cells was reduced by 50% centrally (C) and 36% peripherally (P) (P < 0.001) compared with control eyes. At day 2, there was no statistically significant difference between control and experimental corneas (P = 0.675). At day 4, a marked significant increase in BrdU-labeled cells was noted, averaging 83% (C) and 96% (P) (P < 0.001). At day 7, BrdU-labeling returned to control values, although it was still slightly elevated (14% [C] and 5% [P], P = 0.045).
  
  
  CONCLUSIONS
  The corneal epithelium in the rabbit required at least 1 full week to recover to its stable baseline proliferation rate following only 24 hours of RGP lens wear. Interestingly, hyperproliferation was noted within the limbal, peripheral, and mid-peripheral corneal epithelium 4 days after lens removal.
authors.affiliation: Department of Opthalmology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75039-9057, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Ladage
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yamamoto
authors.forename: David H
authors.initials: DH
authors.lastname: Ren
authors.forename: James V
authors.initials: JV
authors.lastname: Jester
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Petroll
authors.forename: Jan P G
authors.initials: JP
authors.lastname: Bergmanson
authors.forename: H Dwight
authors.initials: HD
authors.lastname: Cavanagh
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D003262:Contact Lenses, Extended-Wear / Q000009:adverse effects; D004261:DNA Replication / Q000502:physiology; D020878:Device Removal; D004847:Epithelial Cells / Q000166:cytology; D019573:Epithelium, Corneal / Q000166:cytology* / Q000502:physiology*; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D011817:Rabbits; D020127:Recovery of Function; D013997:Time Factors
chemical_list: D001973:Bromodeoxyuridine