TELEMETRY–BASED CONTINUOUS PRESSURE MONITORING AS A TOOL TO REVEAL DORZOLAMIDE–INDUCED INTRAOCULAR PRESSURE CHANGES IN OCULAR HYPERTENSIVE CYNOMOLGUS MONKEYS.

Abstract

Abstract: : Purpose: Intraocular pressure (IOP) assessment by radio–telemetry is a unique method to follow drug–induced IOP variations online and for several weeks without the adverse interference of anesthesia. We examined the sensitivity of this method to detect dorzolamide–induced daily IOP changes in ocular hypertensive cynomolgus monkeys. Methods: 3 adult male cynomolgus monkeys were housed under a 12–hour light/12–h dark cycle and standardised conditions. Ocular hypertension was induced unilaterally by argon laser photocoagulation of the trabeculum. The telemetry system was purchased from Transoma Inc., USA and implanted subcutaneously (battery/transmitter) and intravitreously (pressure transducer). In 2 independent studies, the IOP level is measured online during 21 days. On each of the 5 consecutive instillation days, TRUSOPT^TM 2% eye drops were instilled twice (9 a.m. and 4 p.m.) in the hypertensive eyes. Drug–induced IOP variations were assessed by (i) the percentage of IOP decrease relative to baseline levels and (ii) the maximum amplitude of IOP variations. Results: In both studies, an average dorzolamide–induced IOP decrease of approx. 50% of baseline values was observed both during the day and in the night. There is an individual component to the response on the drug in as far as during the instillation week, 2 monkeys showed a lowering of both mean IOP levels and amplitude of the daily IOP variations whereas 1 monkey repeatedly revealed only a decreased amplitude. At the end of the instillation period, the IOP returned to baseline levels within 3 days in all 3 monkeys. Conclusions: The results show that the described telemetry method is sensitive enough to detect the daily variations of the IOP level as well as the typical IOP response to dorzolamide in the ocular hypertensive monkey model.

Keywords: intraocular pressure • pathology: experimental • drug toxicity/drug effects