Corneal thickness changes during corneal collagen cross-linking with UV-A irradiation and hypo-osmolar riboflavin in thin corneas.
OBJECTIVE
To evaluate the thinnest corneal thickness changes during and after corneal collagen cross-linking treatment with ultraviolet-A irradiation, using hypo-osmolar riboflavin solution in thin corneas.


METHODS
Eighteen eyes of 18 patients were included in this study. After epithelium removal, iso-osmolar 0.1% riboflavin solution was instilled to the cornea every 3 minutes for 30 minutes. Hypo-osmolar 0.1% riboflavin solution was then applied every 20 seconds for 5 minutes or until the thinnest corneal thickness reached 400 µm. Ultraviolet-A irradiation was performed for 30 minutes. During irradiation, iso-osmolar 0.1% riboflavin drops were applied every 5 minutes. Ultrasound pachymetry was performed at approximately the thinnest point of the cornea preoperatively, after epithelial removal, after iso-osmolar riboflavin instillation, after hypo-osmolar riboflavin instillation, after ultraviolet-A irradiation, and at 1, 6 and 12 months after treatment.


RESULTS
Mean preoperative thinnest corneal thickness was 380 ± 11 µm. After epithelial removal it decreased to 341 ± 11 µm, and after 30 minutes of iso-osmolar 0.1% riboflavin drops, to 330 ± 7.6 µm. After hypo-osmolar 0.1% riboflavin drops, mean thinnest corneal thickness increased to 418 ± 11 µm. After UVA irradiation, it was 384 ± 10 µm. At 1, 6 and 12 months after treatment, it was 372 ± 10 µm, 381 ± 12.7, and 379 ± 15 µm, respectively. No intraoperative, early postoperative, or late postoperative complications were noted.


CONCLUSIONS
Hypo-osmolar 0.1% riboflavin solution seems to be effective for swelling thin corneas. The swelling effect is transient and short acting. Corneal thickness should be monitored throughout the procedure. Larger sample sizes and longer follow-up are required in order to make meaningful conclusions regarding safety.
Goiania Eye Institute, Goiânia (GO), Brazil. bnassaralla@bol.com.br
Belquiz Amaral
BA
Nassaralla
Diogo Mafia
DM
Vieira
Márcia Leite
ML
Machado
Marisa Novaes Faleiro Chaves de
MN
Figueiredo
João Jorge
JJ
Nassaralla
D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000187:drug effects / Q000528:radiation effects; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000187:drug effects* / Q000528:radiation effects*; D003432:Cross-Linking Reagents / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000601:surgery; D008297:Male; D009994:Osmolar Concentration; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology / Q000627:therapeutic use; D011446:Prospective Studies; D012256:Riboflavin / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors; D016896:Treatment Outcome; D014467:Ultraviolet Therapy / Q000379:methods*; D014792:Visual Acuity; D014803:Vitamin B Complex / Q000494:pharmacology* / Q000627:therapeutic use; D055815:Young Adult
D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D014803:Vitamin B Complex; D003094:Collagen; D012256:Riboflavin