CONTINUOUS INTRAOCULAR-PRESSURE MEASUREMENT BY TELEMETRY IN ALPHA-CHYMOTRYPSIN-INDUCED GLAUCOMA MODEL IN THE RABBIT - EFFECTS OF TIMOLOL, DORZOLAMIDE, AND EPINEPHRINE

The aim of this study was to set-up and validate the use of a radio-te lemetry system in order to record IOP in chronic ocular hypertensive a nimals. The transmitter of a miniaturized radio-telemetry system was i mplanted in rabbits, and its catheter was tunnelled subcutaneously to the superior conjunctival sac and inserted into the midvitreous. Impla ntation was performed in chronic ocular hypertensive rabbits induced b y an injection of alpha-chymotrypsin into the posterior chamber of the eye. The effects of 0.5% timolol maleate, 2% dorzolamide hydrochlorid e and 1% epinephrine were assessed and compared after topical administ ration in this model. Implanted radio-telemetric system into the vitre ous allowed IOP measurement for more than 6 months. In this study, cir cadian IOP kinetic profiles were monitored in all animals over 24 h fo r 3 weeks. Timolol maleate was found significantly potent in reducing IOP, while changes depended on the nyctemeral period. Dorzolamide hydr ochloride induced a very large IOP reduction and was found to be also well effective at night. We evidenced a biphasic time-dependent effect after topical epinephrine, with a long lasting IOP increase occurring after the administration. This change was found to be related to side effects resulting from a poor ocular tolerance of this drug in the ra bbit, leading to either a complete eye closure or a higher blinking ra te. By using our method, we confirmed the pressure pulses and undersho ots occurring during blinking. Radio-telemetry in chronic glaucoma rab bits appears as a refined method to assess anti-glaucoma drug activity , 24 hours a day, for long-term periods in unrestrained animals, while also providing information on the ocular side effects of eye drops. ( C) 1996 Elsevier Science Inc.