Abstract
Purpose :
IOP fluctuations have been strongly associated with the risk of developing glaucoma and glaucoma progression. While no clinical devices are available for routine continuous 24-hour IOP monitoring, animal models can provide important information about the variability of IOP. Recent research in non-human primates (NHPs) has been reported, but the challenges and expense associated with NHP research makes it difficult to use as a model where surgery/invasive procedures are required. Rodent models have also been developed but are too small for invasive procedures performed on human eyes. There is a clear need for a low-cost, large animal model for continuous IOP monitoring and subsequent intervention. The purpose of our study was to develop a rabbit model for 24-hour telemetric IOP monitoring.
Methods :
An implantable telemetric pressure transducer system (TSE-Systems, Chesterfield, MO) was used to measure IOP from the anterior chamber of adult New Zealand White rabbits. Pressure readings were automatically compensated for barometric pressure and recorded at 100 Hz. Manometric IOP sensor calibration was performed biweekly. The IOP signal was digitally filtered for noise and signal dropout, and circadian pattern was assessed after using a 200-second averaging window. Animal motion and temperature were captured using an integrated accelerometer and thermocouple, and housing was kept on a 12-hour light/dark cycle.
Results :
IOP fluctuations occurred frequently and by large magnitudes. A strong nychthemeral pattern was observed, with IOP peak occurring at the end of the light phase or beginning of the dark phase, with peak-to-trough of approximately 8 mmHg (Fig 1). Increased fluctuations were associated with animal motion (Fig 2A). During periods of inactivity, ocular pulse pressures were detectable with a magnitude of 2-4 mmHg (Fig 2B).
Conclusions :
Continuous 24-IOP can be successfully measured telemetrically in rabbits. Large magnitude IOP fluctuations are common. The 24-hour IOP pattern shows a larger difference between peak and trough pressures than human or NHP circadian patterns. Since rabbits are nocturnal, the peak IOP occurs towards the end of the sleeping period, which corresponds to IOP patterns in humans.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.