title: Comparative study of riboflavin-UVA cross-linking and "flash-linking" using surface wave elastometry.
abstract: OBJECTIVE
  To investigate comparative stiffness values in porcine corneas after standard cross-linking and a new, rapid method of cross-linking (flash-linking) using surface wave elastometry.
  
  
  METHODS
  Ten porcine eyes were treated using an ultraviolet A (UVA) double diode light source with a wavelength of 370 nm and delivering an irradiance of 4.2 mW/cm2 at a distance of 1.2 cm while applying 0.1% riboflavin-5-phosphate drops to the central cornea every 5 minutes as a photosensitizer for 30 minutes (riboflavin-UVA group). The next 10 porcine corneas were treated with a single application of a customized photoactive crosslinking agent and 30 seconds of UVA light at the same power and wavelength (flash-linking group). Following treatment, the Sonic Eye system (PriaVision Inc) was used to measure ultrasound surface wave propagation time between two fixed-distance transducers applied to the cornea along central horizontal and vertical positions. Intraocular pressure was continuously monitored.
  
  
  RESULTS
  Mean surface wave velocity was determined from the last 5 of 10 sequential measurements for each eye, and was 90.87 +/- 15.26 m/s for all eyes with a mean standard deviation (SD) of 2.34 m/s among each eye in the riboflavin-UVA group versus 83.66 +/- 12.30 m/s with a mean SD of 2.69 m/s among each eye in the flash-linking group before treatment and 109.2 +/- 21.76 m/s with a mean SD of 2.15 m/s among each eye (riboflavin-UVA group) versus 109.2 +/- 18.42 m/s with a mean SD of 2.26 m/s among each eye (flash-linking group) after cross-linking. The mean surface wave velocity increased by 18.3 units from 90.87 to 109.2 m/s (P = .003) after cross-linking with riboflavin-UVA, and by 25.5 m/s from 83.66 to 109.2 m/s (P = .0001) after flash-linking. Surface wave velocity was noted to increase after both cross-linking techniques, but the differences observed did not reach statistical significance (P = .74).
  
  
  CONCLUSIONS
  A new, rapid method of cross-linking (flash-linking) is introduced by the use of a customized photoactive cross-linking agent. The method demonstrates similar efficacy in stiffening the cornea (when measured with surface wave elastometry) in comparison to standard cross-linking, but requires only 30 seconds of UVA exposure.
authors.affiliation: Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. rochak@ccf.org
authors.forename: Karolinne Maia
authors.initials: KM
authors.lastname: Rocha
authors.forename: Jerome C
authors.initials: JC
authors.lastname: Ramos-Esteban
authors.forename: Ying
authors.initials: Y
authors.lastname: Qian
authors.forename: Satish
authors.initials: S
authors.lastname: Herekar
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Krueger
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000502:physiology*; D003319:Corneal Stroma / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000379:methods; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011205:Povidone / Q000627:therapeutic use*; D012256:Riboflavin / Q000627:therapeutic use*; D013552:Swine; D014466:Ultraviolet Rays
chemical_list: D017319:Photosensitizing Agents; D003094:Collagen; D011205:Povidone; D012256:Riboflavin