title: Corneal Cross-Linking: Evaluating the Potential for a Lower Power, Shorter Duration Treatment.
abstract: OBJECTIVE
  To determine the cross-linking effect of a riboflavin ultraviolet-A (UV-A) corneal cross-linking treatment that is both shorter and has lower energy than the Dresden protocol.
  
  
  METHODS
  In a first experiment, 12 human corneas were presoaked with riboflavin and then irradiated with UV-A at 3 mW/cm after clearing the surface of riboflavin, with no added riboflavin during irradiation. Percent UV-A transmission through the corneas was measured at intervals up to 30 minutes. A second experiment involved 24 porcine corneas. Eight were de-epithelialized, presoaked in riboflavin for 30 minutes, and irradiated at 1.5 mW/cm for 10 minutes. An additional 8 were riboflavin treated and similarly irradiated, but with epithelium intact and a final 8 corneas were not treated. Young modulus was measured in all 24 corneas at the end of the experiment.
  
  
  RESULTS
  The first experiment showed essentially complete riboflavin oxidation after only 10 minutes. Based on these results, a shortened UV-A exposure cross-linking experiment was designed using a reduced UV-A fluence of 1.5 mW/cm, an endothelial exposure within safety limits in humans. With this protocol Young modulus was the same in the irradiated porcine corneas but with epithelium intact as in the untreated corneas. In contrast, Young modulus increased by a factor of 1.99 in the UV-A cross-linked corneas at 1.5 mW/cm for 10 minutes with the epithelium removed.
  
  
  CONCLUSIONS
  A shorter, lower energy protocol than the Dresden protocol seems to provide a significant increase in Young modulus, similar to published results with higher energy, longer exposure protocols.
authors.affiliation: *Corneal Transplant Center, Pellegrini Hospital, Naples, Italy;†I.R.O.S. (Institute of Refractive and Ophthalmic Surgery), Naples, Italy;‡Mercy Center for Corrective Eye Surgery, McHenry, IL;§Department of Pharmacy, University of Salerno, Fisciano, Salerno, Italy;¶Department of Pharmacy, University of Naples Federico II, Naples, Italy;‖Department of Ophthalmology, Pellegrini Hospital, Naples, Italy;**Eye Clinic, University of Naples Federico II, Naples, Italy; and††Department of Ophthalmology, Salerno University Hospital, Salerno, Italy.
authors.forename: Ciro
authors.initials: C
authors.lastname: Caruso
authors.forename: Gaetano
authors.initials: G
authors.lastname: Barbaro
authors.forename: Robert L
authors.initials: RL
authors.lastname: Epstein
authors.forename: Diana
authors.initials: D
authors.lastname: Tronino
authors.forename: Carmine
authors.initials: C
authors.lastname: Ostacolo
authors.forename: Antonia
authors.initials: A
authors.lastname: Sacchi
authors.forename: Luigi
authors.initials: L
authors.lastname: Pacente
authors.forename: Antonio
authors.initials: A
authors.lastname: Del Prete
authors.forename: Marina
authors.initials: M
authors.lastname: Sala
authors.forename: Salvatore
authors.initials: S
authors.lastname: Troisi
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism; D003319:Corneal Stroma / Q000378:metabolism; D003432:Cross-Linking Reagents; D055119:Elastic Modulus; D004548:Elasticity; D006801:Humans; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D011829:Radiation Dosage; D011834:Radiation Monitoring; D012256:Riboflavin / Q000008:administration & dosage*; D013552:Swine; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin