Equivalence of biomechanical changes induced by rapid and standard corneal cross-linking, using riboflavin and ultraviolet radiation.
OBJECTIVE
Ultraviolet (UV) corneal cross-linking is an accepted method for treating corneal ecstatic disorders. The authors evaluated whether a rapid treatment protocol (higher intensity and shorter irradiation time) could achieve the same increase in corneal stiffness as the currently used standard protocol.


METHODS
Stress-strain measurements were performed on porcine corneal strips. The corneas (n = 72) were cut into three strips, each randomly receiving a different treatment: rapid (10 mW/cm(2), 9 minutes), standard (3 mW/cm(2), 30 minutes), or no (control, 0 mW/cm(2)) irradiation. After irradiation, the Young's modulus of each strip was determined. The results of the stress-strain measurements were analyzed statistically.


RESULTS
Statistical analysis showed that, after irradiation, the median value of Young's modulus from both active treatment groups (rapid, 3.83 N/mm(2); standard, 3.88 N/mm(2)) was significantly higher (P < 0.05) than that of the control group (2.91 N/mm(2)). Treatment increased Young's modulus by a factor of 1.3. However, there was no significant difference (P = 0.43) between the rapid and standard groups in the median of Young's modulus.


CONCLUSIONS
Rapid UV cross-linking treatment can be regarded as equivalent to the standard procedure in terms of increase in corneal stiffness. The new rapid protocol shortens the treatment duration by more than two thirds, from 30 to 9 minutes. The safety of the higher intensities must be addressed in further clinical studies.
IROC AG, Institute of Refractive and Ophthalmic Surgery, Stockerstrasse 37, Zurich, Switzerland. silvia.schumacher@iroc.ch
Silvia
S
Schumacher
Lydia
L
Oeftiger
Michael
M
Mrochen
D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000187:drug effects / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D055119:Elastic Modulus; D004548:Elasticity / Q000502:physiology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D012256:Riboflavin / Q000494:pharmacology*; D013552:Swine; D014466:Ultraviolet Rays
D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin