title: Keratoconus corneal architecture after riboflavin/ultraviolet A cross-linking: ultrastructural studies.
abstract: OBJECTIVE
  Study to investigate the effects of collagen cross-linking on the ultrastructural organization of the corneal stroma in the human keratoconus cornea (KC).
  
  
  METHODS
  Three normal, three keratoconus (KC1, KC2, KC3), and three cross-linked keratoconus (CXL1, CXL2, CXL3) corneas were analyzed. The KC corneas were treated with a riboflavin-ultraviolet A (UVA) treatment (CXL) method described by Wollensak et al. Penetrating keratoplasty (PKP) was performed 6 months after treatment. All samples were processed for electron microscopy.
  
  
  RESULTS
  The riboflavin-UVA-treated CXL corneal stroma showed interlacing lamellae in the anterior stroma followed by well-organized parallel running lamellae. The lamellae contained uniformly distributed collagen fibrils (CFs) decorated with normal proteoglycans (PGs). The CF diameter and interfibrillar spacing in the CXL cornea were significantly increased compared to those in the KC cornea. The PG area in the CXL corneas were significantly smaller than the PGs in the KC cornea. The epithelium and Bowman's layer were also normal. On rare occasions, a thick basement membrane and collagenous pannus were also observed.
  
  
  CONCLUSIONS
  Corneal cross-linking leads to modifications of the cornea stroma. The KC corneal structure showed a modification in the CF diameter, interfibrillar spacing, and PG area. This resulted in a more uniform distribution of collagen fibrils, a key feature for corneal transparency.
authors.affiliation: Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University, Saudi Arabia. akhtars@ksu.edu.sa
authors.forename: Saeed
authors.initials: S
authors.lastname: Akhtar
authors.forename: Turki
authors.initials: T
authors.lastname: Almubrad
authors.forename: Iacopo
authors.initials: I
authors.lastname: Paladini
authors.forename: Rita
authors.initials: R
authors.lastname: Mencucci
mesh_terms: D000328:Adult; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000187:drug effects / Q000528:radiation effects* / Q000648:ultrastructure*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D006801:Humans; D007640:Keratoconus / Q000473:pathology*; D011509:Proteoglycans / Q000378:metabolism; D012256:Riboflavin / Q000494:pharmacology*; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D011509:Proteoglycans; D003094:Collagen; D012256:Riboflavin