June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Characterization of transient and sustained intraocular pressure fluctuations in rats
Author Affiliations & Notes
  • Christina M Nicou
    Medical Engineering, University of South Florida, Tampa, Florida, United States
  • Christopher L Passaglia
    Medical Engineering, University of South Florida, Tampa, Florida, United States
  • Footnotes
    Commercial Relationships   Christina Nicou None; Christopher Passaglia None
  • Footnotes
    Support  NH Grant EY027037
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 148 – A0341. doi:
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      Christina M Nicou, Christopher L Passaglia; Characterization of transient and sustained intraocular pressure fluctuations in rats. Invest. Ophthalmol. Vis. Sci. 2022;63(7):148 – A0341.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Although elevated intraocular pressure (IOP) is a major risk factor for glaucoma, little is known about IOP dynamics on different time scales. Most researchers use tonometry to estimate IOP, which gives only pressure snapshots and was shown to induce a stress response in rats. This study sought to characterize the duration, magnitude, and mechanical energy associated with transient and sustained IOP fluctuations in rats.

Methods : Brown-Norway rats underwent an anterior segment cannulation to record IOP from a wireless backpack pressure transducer. Animals were housed in normal light/dark cycle and IOP was sampled at 0.25 Hz for weeks to months. IOP data was mean filtered and analyzed with a peak detection algorithm in MATLAB to characterize transient IOP fluctuations. Sustained IOP fluctuations were determined by interpolating the local minima between peaks. The IOP-related mechanical energy that the eye experiences over time was found by multiplying the area under the transient or sustained curves by the average eye conductance. IOP data was mean-normalized and subjected to a 1-hr statistical analysis to determine daily IOP trends.

Results : Continuous IOP data collected for 246 days in total across 37 animals were analyzed. Based on autocorrelation analysis, transient events were defined as peaks occurring at least 2 minutes apart with a 1 mmHg minimum prominence. There were approximately 219 transients per day that lasted seconds to minutes with magnitudes up to 60 mmHg. The IOP-related mechanical energy associated with transient events was 77 ± 34 mJ/day as compared to 312 ± 345 mJ/day for slow sustained fluctuations in mean IOP. Much of the sustained energy is attributed to the circadian IOP rhythm. The mechanical energy of mean IOP alone was 3455 ± 2303 mJ/day. Distributions of IOP fluctuations failed normality tests and were better described by a dual Gaussian model with standard deviations of 1.9 and 15.3 mmHg, which presumably corresponds to transient and sustained components.

Conclusions : Our results suggest that transient and sustained IOP fluctuations comprise about 10% of the total IOP-related mechanical energy the eye absorbs daily. This is comparable in total energy impact to a 1 mmHg change in mean IOP. The energy of IOP fluctuations is also concentrated in time and thus has considerably more power, which may have implication for glaucoma.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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