Antioxidant protection against corneal damage by free radicals during phacoemulsification

PURPOSE. To examine the role of ascorbic acid in reducing corneal endothelial cell loss secondary to high-energy ultrasound energy during phacoemulsification surgery. METHODS. Seventeen rabbit eyes were subjected to prolonged phacoemulsification within the anterior chamber, without manipulation or damage to other ocular structures. In nine eyes, a balanced salt ophthalmic solution was used as the phacoemulsification irrigation solution, and in eight eyes the solution plus 0.001 M ascorbic acid was used, all other parameters being identical between the two groups. Specular microscopy was performed in all eyes before and 1 week after surgery. The animals were then killed, and the corneas were examined histologically. RESULTS. There was no significant difference in preoperative endothelial cell counts between the two groups. Postoperative cell counts were reduced by 453.9 ± 233.3 (SEM) cells/mm² in the solution-alone group versus 123.2 ± 196.4 (SEM) cells/ mm² in the solution-plus-ascorbic acid group, (P = 0.011). Corneal histology revealed a marked difference in endothelial cell morphology between the two groups. CONCLUSIONS. The addition of ascorbic acid to the irrigation solution significantly reduced the amount of endothelial cell loss during phacoemulsification by approximately 70%. This is thought to be due to the free-radical-scavenging properties of ascorbic acid. Further studies are warranted to find the optimal concentrations and combinations of free radical scavengers to be used in phacoemulsification irrigation solutions.