title: Intrastromal application of riboflavin for corneal crosslinking.
abstract: OBJECTIVE
  To experimentally evaluate the efficacy of corneal crosslinking (CXL) by injecting the photomediator riboflavin into the corneal stroma via intrastromal channels.
  
  
  METHODS
  Five groups of pig corneas, nine each, were compared regarding stress-strain relationship and UV-absorption. Group 1 had intrastromal channels floated with riboflavin 0.5%-solution followed by UVA-irradiation (3 mW/cm(2) for 30 minutes); group 2 was handled like group 1, but were irradiated with 9 mW/cm(2) for 10 minutes; group 3 was treated according to the Dresden protocol (epi-off, 9 mW/cm(2) for 10 minutes); group 4 had the identical channel system, no riboflavin but identical irradiation; group 5 with native corneas served as a control group. The intrastromal channels were created with a femtosecond laser. The stress-strain relations were measured in corneal strips using a uniaxial material tester at strains up to 12%. The UV-transmission of the corneas was measured in groups 1, 3, and 5.
  
  
  RESULTS
  The stress needed for a 10% strain was significantly increased by 82% in the corneas treated with the Dresden protocol compared with native cornea (P = 0.0005). With intrastromal application of riboflavin the significant increase was 87% (P = 0.0005) in group 1 and 64% (P = 0.007) in group 2. The channel formation alone did not alter biomechanics (P = 0.923). The corneal UVA-transmission was 2.4% after intrastromal riboflavin application, 8.9% after the treatment according to the Dresden protocol, and 57.9% in native corneas.
  
  
  CONCLUSIONS
  The experiments demonstrate the intrastromal application of riboflavin by means of intrastromal channels a feasible "epi-on" approach for CXL. More experimental data are needed before clinical testing.
authors.affiliation: The Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland.
authors.forename: Theo G
authors.initials: TG
authors.lastname: Seiler
authors.affiliation: The Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland.
authors.forename: Isaak
authors.initials: I
authors.lastname: Fischinger
authors.affiliation: Universität Zürich, Zürich, Switzerland.
authors.forename: Tim
authors.initials: T
authors.lastname: Senfft
authors.affiliation: Department of Ophthalmology, Universität Wien, Vienna, Austria.
authors.forename: Gerald
authors.initials: G
authors.lastname: Schmidinger
authors.affiliation: The Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland.
authors.forename: Theo
authors.initials: T
authors.lastname: Seiler
mesh_terms: D000818:Animals; D003094:Collagen / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D003319:Corneal Stroma / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D003432:Cross-Linking Reagents; D004195:Disease Models, Animal; D007267:Injections; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D012256:Riboflavin / Q000008:administration & dosage*; D013552:Swine; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin
keywords: cornea; crosslinking; femtosecond laser; keratokonus; riboflavin