Comparative analysis of the effect of riboflavin solutions on the corneal thickness of rabbits

Purpose. To study the effect of isotonicity of riboflavin solutions on corneal thickness in an experiment. Material and methods. The studies were conducted on 9 rabbits (18 eyes) in 3 groups. Photosensitizer solutions developed at the Ufa Research Institute of Eye Diseases were used for instillations on the cornea. In the 1st group, an isotonic solution of riboflavin with hydroxypropyl methylcellulose (HPMC) was used, in the 2nd – isotonic riboflavin, in the 3rd – a hypotonic solution of riboflavin. The studies were performed under general and local anesthesia. Instillation of the studied solutions was carried out for 60 minutes after corneal de-epithelialization: in the 1st group with a frequency of 1 drop per 2 minutes, in the 2nd and 3rd at the rate of 1 drop per 1 min. The corneal thickness of rabbits was determined using optical coherence tomography (Vizante OCT, Germany) every 5 min for 1 hour. The Microsoft Excel 2010 and Statistika 6.0 software packages were used for statistical analysis. Results. In all groups, after epithelial debriment a slight decrease in corneal thickness was observed by an average of 11±3.9 μm. Isotonic solutions during instillation maintained a stable thickness of the deepithelialized cornea. In group 1, the range of values was from 338 to 366 μm, with an intact corneal thickness of 374±23.1 μm, in group 2 – from 386 to 365 μm, with an intact corneal thickness of 379±28.2 μm. No statistically significant difference was found between the groups. The hypotonic solution (group 3) induced pronounced stromal edema and demonstrated a stable tendency to increase corneal thickness by 13% to 449.6±160.4, compared with its intact state (390.1±36.4 μm). Conclusion. Using of isotonic (group 1 and 2) and hypotonic (group 3) riboflavin solutions resulted in a short-term slight decrease in corneal thickness against the background of deepithelialization with subsequent stable maintenance of the index in the range ensuring safe surgical intervention. Using the hypoosmotic riboflavin, an increase in corneal thickness was observed up to 13%, which allows this solution to be used in clinical practice in patients with thin corneas (less than 450 μm) under intraoperative control. Key words: keratoconus, ultraviolet crosslinking of the cornea, photosensitizers, riboflavin, corneal thickness