CIRCADIAN RHYTHM OF INTRAOCULAR PRESSURE IN MINIPIGS: FIRST TIME MAPPING OF RHYTHMICITY AND RESPONSE TO ENVIRONMENTAL AND PHARMACEUTICAL FACTORS
Abstract: The existence of a daily circadian rhythm of IOP in pigs has not been previously investigated. The aim of this study was to determine if there is rhythmicity to minipig IOP under a regular light/dark cycle and the effect of reversing light/dark cycles on IOP rhythmicity. Eight female minipigs were exposed to regular light/dark cycles. Four baseline IOP collections were taken at least 10 days apart and were 24 hours, with IOP taken from both eyes every two hours using a Reichert Tonopen XL. Light/dark cycles were flipped 10 days prior to reversed data collection. Baseline data was analyzed by repeated measures ANOVA and there was a significant effect of time, F(11,77)=10.16,p< 0.001. Bonferroni post hoc tests revealed a significant difference between hour 0 and 6 (p=0.01), 6 and 10 (p=0.004), 10 and 14, (p<0.001) and between 14 and 0 (p=0.008). There were IOP peaks at hours 6 and 14, and troughs at hours 10 and 0, supporting the hypothesis that minipigs have a daily rhythmicity to their IOP. Reversed light/dark data were analyzed by repeated measures ANOVA and there was an effect of time, (p <0.001) but there was a difference between the established IOP baseline time points and reversed IOP time points (p <0.05), suggesting a disruption from the regular light/dark cycle. For the Timolol hypothesis, a repeated measures ANOVA was run with time (2 hr bins) as the within subjects factor. There was a no significant difference between the established baseline and the control eye over time, F(1,14) = 1.814 p=0.19. This research is significant because the rhythm of IOP is being investigated as an important risk factor for the progression of Glaucoma, an eye disease causing unreversed vision loss, and pigs could serve as a valuable animal model, now that their IOP rhythm has been mapped.
Abigail Christie*, Kimberly Guay, PhD, Amber Harris Bozer, PhD, Jolena Waddell, PhD, and Ryan Ridges, MD
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