Corneal crosslinking: riboflavin concentration in corneal stroma exposed with and without epithelium.
OBJECTIVE
To evaluate intrastromal concentrations of riboflavin with and without epithelium to ensure the efficacy and safety of corneal crosslinking (CXL) by the standard and transepithelial procedures.


METHODS
Department of Ophthalmology and Department of Pharmacology G. Segre, Siena University, Siena, Italy.


METHODS
This study comprised keratoconic patients enrolled for penetrating keratoplasty (PKP) and warm-stored sclerocorneal rings unsuitable for transplantation. Half the PKP specimens were debrided, and half were left with the epithelium in situ. One of the latter and 1 debrided sample were not exposed to riboflavin (controls). Samples in both groups were soaked with 0.1% riboflavin-dextran 20% solution instilled every 2 minutes for 5, 15, and 30 minutes. Riboflavin concentrations were determined by high-performance liquid chromatography (HPLC).


RESULTS
The study evaluated 14 PKP specimens and 16 sclerocorneal rings. Control samples did not show a riboflavin emission peak. In exposed samples with epithelium, the mean riboflavin concentration was 91.88 ng/g after 5 minutes of exposure, 95.60 ng/g after 15 minutes, and 94.92 ng/g after 30 minutes. In the debrided samples, the mean riboflavin concentration was 14.42 microg/g, 20.92 microg/g, and 24.06 microg/g, respectively. No differences were seen between the in vivo samples and the ex vivo samples.


CONCLUSIONS
The HPLC quantitative study showed that stromal concentrations of riboflavin increased with exposure time only if the epithelium was removed. A theoretically safe and effective riboflavin concentration of 15 microg/g was obtained for ultraviolet A-induced CXL only after the epithelium was removed and after at least 10 minutes of riboflavin application every 2 minutes.
Baiocchi
Stefano
S
Department of Ophthalmology, Santa Maria delle Scotte Hospital, Siena University, Siena, Italy.
Mazzotta
Cosimo
C
Cerretani
Daniela
D
Caporossi
Tomaso
T
Caporossi
Aldo
A
D000328:Adult; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000378:metabolism; D003319:Corneal Stroma / Q000378:metabolism*; D003646:Debridement; D019573:Epithelium, Corneal / Q000378:metabolism*; D005125:Eye Banks; D006801:Humans; D007640:Keratoconus / Q000601:surgery*; D015948:Keratoplasty, Penetrating; D008875:Middle Aged; D017319:Photosensitizing Agents / Q000493:pharmacokinetics*; D012256:Riboflavin / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014019:Tissue Donors; D055815:Young Adult
D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin