Abstract
Introduction: :
Elevated intraocular pressure (IOP) is a primary risk factor for glaucoma. Continuous IOP measurement would allow physicians to track IOP changes caused by disease, diurnal variation or ongoing therapy and could be a breakthrough in monitoring glaucoma treatment and following glaucoma pathologies.
Methods: :
White New Zealand rabbits, anesthetized with ketamine/acepromazine, had a transmitter/battery pack implanted into a dorsal neck pocket, which was connected to a solid state pressure sensor inserted into the posterior chamber. A separate pressure sensor monitored local barometric pressure changes. Sensors were calibrated by a tonometer. Continuous readings (10/sec) from this system were recorded for 15 sec every 15 min, but this timing and sampling rate was adjustable. The free roaming rabbits were maintained in a room with a computer data collection system. Topical ocular compression and drugs such as atropine (1%) or timolol (0.5%) were applied.
Results: :
–There were no surgical failures or significant infections.
–The microwave signal was detectible by the transceiver from at least 20 feet.
–Multiple implanted animals (2 rabbits) were tracked at the same room with the same computer.
–A long–term implant study using two rabbits (currently more than 2 months) showed no rejection or ocular damage.
–Data from the system reflected the diurnal variation in IOP.
–The system detected a decrease in IOP after timolol and an IOP increase by topical ocular compression, but atropine had little effect.
–There was no impairment of normal visual function as measured by slit lamp, tonometry or confocal microscopy.
–Battery/transceiver replacement was accomplished without impairment of the animal or the transducer in situ.
Conclusions: :
This system reported continuous IOP for more than two months. It is capable of detecting diurnal, pharmacological and physiological IOP changes and monitoring up to 12 animals. Proposed reductions in size and power consumption would permit implantation in glaucoma patients.
Keywords: intraocular pressure