title: Histological findings in a failed corneal riboflavin-UVA collagen cross-linking performed for progressive keratoconus.
abstract: OBJECTIVE
  To report the histological and immunohistochemical findings in a cornea removed from a patient who had undergone collagen cross-linking (CXL) with riboflavin and ultraviolet-A for progressive keratoconus. CXL was performed following the Siena protocol. Two years post-CXL, a visual acuity impairment in the treated eye secondary to corneal stromal opacity had occurred, together with corneal thinning and flattening.
  
  
  METHODS
  The excised cornea was formalin-fixed, paraffin-embedded, and examined microscopically. Deparaffinized 4-μm sections were stained with hematoxylin-eosin and Masson trichrome. Further tissue sections were subjected to immunohistochemical evaluation of CD34 and Ki-67 antigens.
  
  
  RESULTS
  Histologically, there was no scar tissue in the failed cornea. The biomicroscopic stromal opacity corresponded microscopically to an acellular area, devoid of keratocytes, and to compaction of the lamellar collagen. Amorphous, weakly eosinophilic interlamellar deposits, extending from the anterior to the posterior two thirds of the stroma, were noted.
  
  
  CONCLUSIONS
  CXL is a promising procedure for the treatment of progressive keratoconus with minimal reported side effects. In the present case, we speculate that the short corneal soaking time (15 minutes according to the Siena protocol) may have resulted in inefficient ultraviolet-A blocking, thermal injury, and deeper keratocyte death. Inadequate keratocyte stem cells reservoir could also play a role in individual cases.
authors: Department of Experimental Medicine and Pathology, First Faculty of Medicine, University of Rome, Sapienza, Rome, Italy. irene.pecorella@uniroma1.it
authors: Irene
authors: I
authors: Pecorella
authors: Rossella
authors: R
authors: Appolloni
authors: Alessandro
authors: A
authors: Tiezzi
authors: Pasquale
authors: P
authors: Plateroti
authors: Rocco
authors: R
authors: Plateroti
mesh_terms: D000328:Adult; D018952:Antigens, CD34 / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000378:metabolism*; D019781:Corneal Topography; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D015948:Keratoplasty, Penetrating; D019394:Ki-67 Antigen / Q000378:metabolism; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012256:Riboflavin / Q000627:therapeutic use*; D041623:Tomography, Optical Coherence; D017211:Treatment Failure; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology
chemical_list: D018952:Antigens, CD34; D003432:Cross-Linking Reagents; D019394:Ki-67 Antigen; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin