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CHRONIC IOP TELEMETRY
Telemetry Device
Telemetry Device
The Passaglia lab has developed a wearable wireless telemetry system for chronic recording of IOP in the ambulatory rat (shown in video below). This system collects IOP at 0.25Hz, allowing the highest resolution analysis of IOP in the ambulatory rat to date.
IOP Telemetry System
Figure from Nicou and Passaglia (2021)
IOP Telemetry System
Figure from Nicou and Passaglia (2021)
Key Findings with Telemetry Device
Key Findings with Telemetry Device
Since implementing this device, it has been used to study how IOP in the Brown Norway rat changes on a circadian (~24hr) time scale and on shorter timescales.
Below, left: IOP elevates from approximately 15mmHg during the light phase to 25-30mmHg during the light phase without developing glaucomatous damage that one might expect with elevated intraocular pressures. This device allows the study of this phenomenon continuously for weeks.
Below, right: IOP varies on much smaller timescales as well, and with a custom algorithm (A), variation in the IOP data collected with the telemetry system can be parsed into one of three categories (B): transient fluctuations associated with locomotor activity, sustained fluctuations associated with other physiological processes, or baseline IOP which is the resulting waveform after removing the other fluctuations.
Circadian Rhythmicity of IOP
Figure from Bello and Passaglia (2017)
Circadian Rhythmicity of IOP
Figure from Bello and Passaglia (2017)
IOP Variation on Several Timescales
Figure from Nicou and Passaglia (2024)
IOP Variation on Several Timescales
Figure from Nicou and Passaglia (2024)
Current PhD student, Alexandra Zamitalo, is continuing work with this device for circadian applications.
Current PhD student, Kinnera Khareedu, is continuing work with this device for glaucoma studies.
Current PhD students, Cesar Hernandez Isidro and Alexandra Zamitalo, have modified this device for other telemetry applications.
ACUTE ICP ELEVATION CAUSES IOP ELEVATION
Intraocular (IOP) and intracranial pressures (ICP) both act on the optic nerve head. The Passaglia lab studies relationships between these two pressures, including how they might influence each other.
Experimental Design and Results
Experimental Design and Results
In the anesthetized rat, various physiological parameters including IOP and mean arterial blood pressure are recorded or manipulated.
Below, left: (A) ICP is elevated by infusing saline into the lateral ventricle. The response of IOP and MAP to this manipulation of ICP are recorded. (B) Successful targeting of the lateral ventricle is confirmed using histological techniques.
Below, right: ICP elevation was found to reduce the conventional outflow facility causing an increase in IOP. The results of this paper indicate that this is the result of a neural feedback mechanism to the eye.
Experimental Set-Up
Figure from Ficarrotta and Passaglia (2020)
Experimental Set-Up
Figure from Ficarrotta and Passaglia (2020)
ICP Elevation Increases IOP by Reducing Outflow Facility
Figure from Ficarrotta and Passaglia (2020)
ICP Elevation Increases IOP by Reducing Outflow Facility
Figure from Ficarrotta and Passaglia (2020)
Current PhD student, Cesar Hernandez-Isidro, is continuing work on this project.
PORTABLE FEEDBACK-CONTROLLED PUMP FOR IOP MODULATION IN AMBULATORY RATS
Until the creation of this device, there was no way to modulate the IOP of the freely-moving rodent. This device is equipped with a pressure sensor and an infusion pump which, in combination, allow monitoring out conventional outflow facility in conscious rats.
Pump Design
Pump Design
The portable feedback-controlled pump manipulates IOP by infusing fluid into the eye via a permanently-implanted cannula. Manipulation of IOP in this manner can be used to measure the resistance of the conventional outflow pathway (the inverse of which is conventional outflow facility). Other applications of this device might be to induce ocular hypertension by supplying a continuous infusion into the eye.
Portable Feedback-Controlled Pump
Figure from Mohamed and Passaglia (2023)
Portable Feedback-Controlled Pump
Figure from Mohamed and Passaglia (2023)
Current PhD student, Kinnera Khareedu, is continuing work with this device for glaucoma studies.
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