Abstract
Purpose :
Recent retrospective clinical studies and animal experiments have suggested that cerebrospinal fluid pressure (CSFP) is important in glaucoma and Spaceflight Associated Neuro-Ocular Syndrome (SANS) pathogenesis. Intraocular pressure (IOP) and CSFP are the driving components of translaminar pressure difference (TLPD=IOP-CSFP), which directly affects the optic nerve head and contained lamina cribrosa. The lack of continuous and accurate CSFP measurement has impeded research into the role of TLPD in glaucoma and SANS.
Methods :
We have developed an implantable pressure telemetry system based on a small piezoelectric sensor with low drift. Unilateral IOP is measured from the anterior chamber, intracranial pressure (ICP, a surrogate measure of CSFP) is measured in the brain parenchyma, and arterial blood pressure (BP) is measured in the femoral artery. For this study, we measured physiologic pressures in four nonhuman primates (NHPs) continuously at 200Hz for 30 seconds per body position for three sessions.
Results :
Data were collected in four male rhesus macaques (Figure 1) for varying body positions, with 30s of continuous pressure data averaged at each position. TLPD was quantified as IOP-ICP. Relative change of IOP (n= 2 NHPs), ICP (n=4 NHPs), and TLPD (n=2 NHPs) were compared for changes in body position: supine to prone, supine to seated, supine to standing and supine to inverted (Figure 1). Results show that relative change in ICP and TLPD changes significantly with different body positions (Figure 1), with the greatest relative changes observed when moving from supine to either the seated, (ICP -13.5±2.1 p< 0.0001 and TLPD +11.4±0.7 p< 0.01), standing (ICP -12.1±2.9 p< 0.001 and TLPD +8.6±1.5 p< 0.03) or inverted (ICP +19.7±0.9 p< 0.001 and TLPD -8.9±4.8) positions.
Conclusions :
Development of this novel NHP model with continuous telemetry of IOP, ICP and TLPD variability will allow evaluation of the hypothesis that IOP, ICP, and/or TLPD fluctuations contribute independently to glaucoma onset and/or progression, as well as to investigate the mechanisms underlying SANS.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.