Dextran 70 solutions for the intra‐operative control of corneal hydration in rabbit corneas

Abstract

Abstract Purpose In terms of excimer laser ablation, the cornea is water bound on an organic matrix. Corneal hydration might affect the excimer laser ablation rate, which could affect the accuracy of correction. It was the purpose of the study to investigate the use of Dextran solutions of varying concentrations to control corneal hydration in rabbit corneas. Methods The corneal epithelium was removed by means of a rotating brush from both eyes of 10 anesthetized pigmented rabbits . The Dextran 70 solutions,with concentrations ranging from 1 to 7%, was topically applied to the eyes for two minutes. The thickness of the cornea in each eye was determined by ultrasound pachymetry after epithelial removal and immediately after rinsing. The Dextran concentration corresponding to zero change in pachymetry was determined by linear regression. In a different series of experiments, rabbit corneas were either overhydrated by means of rinsing with saline or left exposed to dehydrate. Following this artificial change in hydration the corneas were rinsed for 2 minutes with the previously determined iso‐osmotic concentration. Results A strong negative correlation between Dextran concentration and change in pachymetry was observed. Rinsing with the isotonic concentration (2.6%) regulated pachymetry whithin 2% of the original value. Conclusion Corneal hydration can be regulated intraoperatively by means of appropriate Dextran solutions. This may prove useful in cases that hydration is potentially different from normal such as in the case of extensive surgical manipulations prior to laser ablation.