Effect of Topically – Applied Carvedilol on Intraocular Pressure in Normal and Ocular Hypertensive Rabbits

Abstract

Background: In glaucoma, as optic neuropathy gradually proceeds unnoticed by the patient, early detection and treatment is of paramount importance in arresting or controlling the progress of damage.
Aim of the study: To explore effects of topical carvedilol on intraocular pressure (IOP) in each of normotensive and ocular hypertensive eyes of rabbits, with assessment of drug safety.
Material and methods: A group of 54 males rabbits were included in this study. Induction of ocular hypertension was achieved by injection of hydroxy propyl methylcellulose in the anterior chamber of rabbits right eye. The present study was designed to evaluate the possible beneficial therapeutic effect (part I) and both prophylactic as well as therapeutic effect (part II). The included rabbits were divided into distilled water group, timolol (0.25% and 0.5%) groups, and carvedilol (0.25% and 0.5%). Each of drug eye drops (including distilled water) were instilled into right eyes 3 times/day for 4 days prophylactically and for 10 days therapeutically. The rabbits had been examined for the IOP, pupil diameter, light reflex, corneal reflex, and conjunctival redness prior to instillation of drugs and along the trial period.
Results: Ocular hypotensive effects of carvedilol (0.25%) and (0.5%) eye drops were more efficient than that of distilled water (P<0.01). Furthermore, carvedilol (0.25%) eye drop simulated timolol (0.25%) eye drop (P>0.05) in its ocular hypotensive effect along the trial period .
Carvedilol eye drop required 4 days of instillation into normotensive eyes to achieve highly significant (P<0.01) ocular hypotensive effect whereas 10 days were needed to do so in ocular hypertensive eyes; such ocular hypotensive effect was more efficient than that of distilled water, but less efficient than that of timolol eye drop.
In both parts of the present study and regarding each of mean pupil diameter, light reflex, corneal reflex and conjunctival redness, carvedilol (0.25% or 0.5%) eye drops had no significant adverse effect (P > 0.05).
Conclusions: Carvedilol eye drops instilled 3 times / day had an obvious prophylactic role in normotensive and a beneficial, safe, and tolerable therapeutic ocular hypotensive effects on hydroxy propyl methyl cellulose - induced ocular hypertension in rabbits .