title: Ultraviolet-visible light spectral transmittance of rabbit corneas after riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking.
abstract: OBJECTIVE
  To determine the effect of riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking on the transmission of the ultraviolet-visible (UV-VIS) light spectrum through the cornea.
  
  
  METHODS
  Twelve New Zealand white male rabbits were used in this research. Cross-linking was performed unilaterally on the right eyes of the animals while only the epithelium was removed on the left eyes as the control. Seven weeks after cross-linking, the animals were euthanized, and the enucleated eyes were processed for transmission spectroscopy. To confirm that the cross-linking procedures was done successfully on the right corneas, the tensile force-extension relationship was measured using six corneas from three of the rabbits after the transmission spectrum was determined.
  
  
  RESULTS
  Seven weeks after cross-linking, ten of the 12 rabbits had clear corneas in the cross-linked and control eyes. The two rabbits with neovascularization and granular opacities in the right corneas were not included in subsequent measurements. In the cross-linked corneas, transmittance was 87.57% at 650 nm, and decreased continuously as the wavelength shortened. From 315 nm, the transmittance rapidly decreased and was 35.52% at 300 nm. In the control corneas, transmittance was 95.95% at 650 nm and decreased continuously as the wavelength shortened. Below 315 nm, the transmittance rapidly decreased, to 40.29% at 300 nm. The transmittance of the cross-linking corneas was 10%-20% lower than that of the control corneas. The difference was 8.38% at 650 nm and increased as the wavelength shortened, reaching a maximum of 20.59% at 320 nm, and decreased rapidly to 4.77% at 300 nm. The tensile force-extension relationship showed that a greater force was necessary to extend the cross-linking corneas over 500 µm than that of the control corneas.
  
  
  CONCLUSIONS
  The transmittance of the cross-linked corneas was 10%-20% lower than that of the control corneas. The difference increased as the wavelength decrease, reaching a maximum at 320 nm and then decreasing rapidly. Ultraviolet collagen cross-linking exhibited a protective effect against ultraviolet penetration.
authors.affiliation: Department of Ophthalmology & Visual Science, College of Medicine, Catholic University of Korea.
authors.forename: Ho Sik
authors.initials: HS
authors.lastname: Hwang
authors.forename: Man Soo
authors.initials: MS
authors.lastname: Kim
mesh_terms: D000818:Animals; D003094:Collagen / Q000494:pharmacology*; D003315:Cornea / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004487:Edema / Q000473:pathology; D020287:In Situ Nick-End Labeling; D008297:Male; D011817:Rabbits; D012256:Riboflavin / Q000494:pharmacology*; D013056:Spectrophotometry, Ultraviolet; D013194:Staining and Labeling; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D003094:Collagen; D012256:Riboflavin