title: The effect of standard and high-fluence corneal cross-linking (CXL) on cornea and limbus.
abstract: OBJECTIVE
  When treating peripheral ectatic disease-like pellucid marginal degeneration (PMD), corneal cross-linking with UV-A and riboflavin (CXL) must be applied eccentrically to the periphery of the lower cornea, partly irradiating the corneal limbus. Here, we investigated the effect of standard and double-standard fluence corneal cross-linking with riboflavin and UV-A (CXL) on cornea and corneal limbus in the rabbit eye in vivo.
  
  
  METHODS
  Epithelium-off CXL was performed in male New Zealand White rabbits with two irradiation diameters (7 mm central cornea, 13 mm cornea and limbus), using standard fluence (5.4 J/cm(2)) and double-standard fluence (10.8 J/cm(2)) settings. Controls were subjected to epithelial removal and riboflavin instillation, but were not irradiated with UV-A. Following CXL, animals were examined daily until complete closure of the epithelium, and at 7, 14, 21, and 28 days. Animals were killed and a corneoscleral button was excised and processed for light microscopy and immunohistochemistry.
  
  
  RESULTS
  For both irradiation diameters and fluences tested, no signs of endothelial damage or limbal vessel thrombosis were observed, and time to re-epithelialization was similar to untreated controls. Histological and immunohistochemical analysis revealed no differences in the p63 putative stem cell marker expression pattern.
  
  
  CONCLUSIONS
  Even when using fluence twice as high as the one used in current clinical CXL settings, circumferential UV-A irradiation of the corneal limbus does not alter the regenerative capacity of the limbal epithelial cells, and the expression pattern of the putative stem cell marker p63 remains unchanged. This suggests that eccentric CXL may be performed safely in PMD.
authors: Department of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland.
authors: Olivier
authors: O
authors: Richoz
authors: Department of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland.
authors: David
authors: D
authors: Tabibian
authors: Department of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland.
authors: Arthur
authors: A
authors: Hammer
authors: Hôpital Ophtalmique Jules Gonin, Lausanne, Switzerland.
authors: François
authors: F
authors: Majo
authors: Hôpital Ophtalmique Jules Gonin, Lausanne, Switzerland.
authors: Michael
authors: M
authors: Nicolas
authors: Department of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland Keck School of Medicine, University of Southern California, Los Angeles, California, United States.
authors: Farhad
authors: F
authors: Hafezi
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D019573:Epithelium, Corneal / Q000378:metabolism; D007150:Immunohistochemistry; D053558:Keratin-3 / Q000378:metabolism; D016850:Limbus Corneae / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011817:Rabbits; D012256:Riboflavin / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D015415:Biomarkers; D003432:Cross-Linking Reagents; D053558:Keratin-3; D017319:Photosensitizing Agents; D014157:Transcription Factors; D012256:Riboflavin
keywords: corneal cross-linking; epithelial regeneration; high fluence; limbal stem cells; p63