title: Effect of eyelid closure and overnight contact lens wear on viability of surface epithelial cells in rabbit cornea.
abstract: OBJECTIVE
  To determine the effects of open, closed eye, and overnight contact lens wear on homeostatic epithelial surface cell death in the rabbit cornea.
  
  
  METHODS
  One eye of each rabbit was either closed by eyelid suture or fitted with one of the following test contact lenses: (1) low Dk/t rigid gas permeable (RGP) lens, (2) hyper Dk/t RGP lens, (3) hyper Dk/t soft lens. The other eye served as a control. After 24 hours, whole corneas were carefully excised and immediately stained with a calcein-acetoxymethyl ester-ethidium homodimer viability assay to quantify the number of nonviable surface epithelial cells. In addition, exfoliated corneal epithelial cells were collected with an eye irrigation chamber to determine cell viability.
  
  
  RESULTS
  In the normal cornea, open-eye conditions showed significantly more nonviable surface cells in the central cornea than in the periphery (p < 0.05). Overnight wear of all test lenses and eyelid closure induced significant decreases in the number of nonviable cells on the central corneal surface compared with controls (p < 0.05). All exfoliated corneal epithelial cells collected by eye irrigation were nonviable.
  
  
  CONCLUSIONS
  In the rabbit model, overnight contact lens wear significantly downregulated spontaneous epithelial surface cell death independent of lens rigidity or material oxygen transmissibility. These effects were similar to eyelid closure without lens wear. Taken together, these results suggest that eyelid closure and the physical presence of the contact lens may protect against the shear stress forces exerted by eyelid blinking, which are believed to cause central surface cell death and subsequent exfoliation.
authors.affiliation: Department of Ophthalmology, The University of Texas Southwestern Medical Center at Dallas, 75390-9057, USA.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Ladage
authors.forename: David H
authors.initials: DH
authors.lastname: Ren
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Petroll
authors.forename: James V
authors.initials: JV
authors.lastname: Jester
authors.forename: H Dwight
authors.initials: HD
authors.lastname: Cavanagh
mesh_terms: D000818:Animals; D001767:Blinking / Q000502:physiology; D002470:Cell Survival / Q000502:physiology*; D003261:Contact Lenses; D003315:Cornea / Q000166:cytology*; D004847:Epithelial Cells / Q000502:physiology*; D005143:Eyelids / Q000502:physiology*; D005452:Fluoresceins; D011817:Rabbits; D012683:Sensory Deprivation
chemical_list: D005452:Fluoresceins; C085925:calcein AM