Effect of Various Compositions of Riboflavin Eye Drops on the Intraoperative Corneal Thickness during UVA-Cross-Linking in Keratoconus Eyes

Background: During the UVA-cross-linking treatment in keratoconus patients, the UVA rays are partially absorbed in the stroma of the riboflavin-loaded cornea. This effect protects the corneal endothelium from UVA irradiation damage. The intensity of UVA light reaching the endothelium is inversely correlated with corneal thickness. The common composition of riboflavin eye drops may lead to a marked reduction in corneal thickness increasing the risk of endothelial damage. Patients and Methods: In a retrospective analysis of 23 UVA-cross-linking procedures on 23 patients we collected data about the pre-, intra- and postoperative corneal thickness (measured with ultrasound). Among these patients and depending on the preoperative state, 8 eyes received Medio Cross (TM) eye drops (group 1), 8 eyes received Medio Cross (TM) eye drops combined with riboflavin 0.1%/methylhydroxypropylcellulose 1,5%/NaCl 1.1% (group 2) and 7 eyes received riboflavin 0.2%/methylhydroxypropylcellulose 0.5%/NaCl 0.7% eye drops (group 3) before and during UVA irradiation. Data are presented as means standard deviation. A comparison of the data was performed using (one-way) ANOVA. Results: The mean corneal thickness at the end of the UVA cross-linking procedure was 67 +/- 9% (means standard deviation) of preoperative thickness in group 1, 118 +/- 14% in group 2 and 140 +/- 23% in group 3. The values in groups 2 and 3 were significantly different from those in the reference group 1. Conclusions: Our results show a strong variability of the postoperative corneal thickness using different standard compositions of riboflavin eye drops. Further studies are needed to find a composition of riboflavin eye drops ensuring a moderate increase in intraoperative corneal thickness to protect the corneal endothelium.