Toxic effects of topically administered Betagan, Betoptic, and Timoptic on regenerating corneal epithelium

Re-epithelialization of 40 iatrogenic cornea ulcers produced in rabbits with iodine vapour burn were studied after topical administration of Betagan, Betoptic or Timoptic. At 24 hours there was no statistical difference in the wound healing rates among all the treated animal groups. At 48 hours, all the drug-treated groups were significantly different from the control group (p less than 0.05). There was no difference between the Betagan and Betoptic treated groups but the Timoptic-treated group was slower (p less than 0.05) than the Betoptic treated group, while the difference between the Timoptic and Betagan treated groups is not significant. At 72 hours the re-epithelialization rate of the Timoptic treated group was significantly slower than both the Betagan and Betoptic treated groups (p less than 0.05). By the 16th day following ulceration SEM examination revealed the Timoptic treated group had extensive epithelial cell desquamation, as well as hole formation and plasma membrane disruption. The Betagan treated corneas had mild superficial epithelial changes with loss of microvilli or slight desquamation. The Betoptic treated corneas were completely healed. In conclusion, Betagan is less toxic than Timoptic. Betoptic is the least toxic of the three drugs to regenerating rabbit corneal epithelium.