Abstract
Purpose :
Long-term and short-term fluctuations in intraocular pressure (lOP) influence glaucoma development and progression. However, the role of ultrashort-term fluctuations, occurring over seconds to minutes, has yet to be determined. This study assesses the utility of cosinor analysis to measure the quantity and magnitude of ultrashort-term fluctuations in continuous 24-hour telemetric lOP data in rabbits.
Methods :
Telemetric pressure transducers (Stellar, TSE-Systems, Chesterfield, MO) were used to measure IOP in adult New Zealand White rabbits. lOP was measured continuously at 100 Hz for one week, filtered, calibrated, and segmented into 24-hour files. Mean IOP was calculated with 60-second averaging intervals. Cosine curves were fit to the data using least squares regression analysis in Microsoft Excel. Mean deviation, largest deviations, and quantity of deviations greater than five mmHg were extracted for each 24-hour segment and subdivided into 12-hour light and dark intervals. Magnitude and quantity of deviations between light and dark hours were compared using paired t-tests.
Results :
Mean deviations of the 60-second mean filtered IOP from the fitted curves remained between -0.6 and 0.6 mmHg. Mean deviations during the dark hours were more positive than those during the light hours (Table 1). Deviations above 5 mmHg were greater during the dark hours than light hours (p < 0.001). Qualitatively, a rapid increase in IOP at the light-to-dark transition was poorly approximated by the cosine curve (Figure 1).
Conclusions :
The narrow range of mean deviations supports accurate approximation of IOP circadian patterns using cosine curves. More positive mean deviations during the dark hours may reflect the greater quantity of positive fluctuations or the qualitative gap at the transition to darkness. Cosinor analysis of continuous IOP data in rabbits can be used for future investigation of factors that affect circadian rhythms, and determining the role of ultrashort-term fluctuations in glaucoma development and progression.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.