Significance of the riboflavin film in corneal collagen crosslinking.
OBJECTIVE
To evaluate the role of the preocular riboflavin film in ultraviolet-A (UVA) absorption in corneal collagen crosslinking (CXL).


METHODS
Eye Laser Institute, Department of Ophthalmology, Martin-Luther-University, Halle, Germany.


METHODS
The absorption of UVA light was measured in human donor and porcine postmortem corneas with and without riboflavin film using 3 solutions: standard dextran-riboflavin, methylcellulose-riboflavin, and hypoosmolar riboflavin-sodium chloride without dextran. The breakup time of the solutions and their absorbance were also determined.


RESULTS
After 30-minute instillation of riboflavin solution, the corneal absorption coefficient of the combined stroma-riboflavin film system was 56.36 cm(-1) in human corneas and 51.46 cm(-1) in porcine corneas using dextran-riboflavin; 69.87 cm(-1) and 53.86 cm(-1), respectively, using methylcellulose-riboflavin; and 48.19 cm(-1) and 42.68 cm(-1), respectively, using hypoosmolar riboflavin. For the stroma alone without riboflavin film, the absorption coefficient was reduced to 36.95 cm(-1) in human corneas and 28.91 cm(-1) in porcine corneas using dextran-riboflavin; 38.26 cm(-1) and 32.49 cm(-1), respectively, using methylcellulose-riboflavin; and 38.88 cm(-1) and 28.42 cm(-1), respectively, using hypoosmolar riboflavin solution. The breakup time was 22 minutes for the dextran-riboflavin film, 32 minutes for methylcellulose, and 90 seconds for the hypoosmolar solution.


CONCLUSIONS
Results indicate that the cornea including the riboflavin film can be considered a composite 2-compartment system and that the riboflavin film is an integral part of the CXL procedure and important in achieving the correct stromal and endothelial UVA irradiance.


BACKGROUND
No author has a financial or proprietary interest in any material or method mentioned.
Wollensak
Gregor
G
Department of Ophthalmology, Eye Laser Institute, Martin-Luther-University, Halle, Germany. gwollens@hotmail.com
Aurich
Henning
H
Wirbelauer
Christopher
C
Sel
Saadettin
S
D000818:Animals; D003094:Collagen / Q000378:metabolism / Q000528:radiation effects*; D003316:Corneal Diseases / Q000188:drug therapy / Q000378:metabolism*; D003319:Corneal Stroma / Q000378:metabolism / Q000528:radiation effects*; D006801:Humans; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use; D012256:Riboflavin / Q000493:pharmacokinetics* / Q000627:therapeutic use; D013552:Swine; D041623:Tomography, Optical Coherence; D014466:Ultraviolet Rays
D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin