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. 2023 Mar;48(3):289-296.
doi: 10.1080/02713683.2022.2141782. Epub 2022 Nov 10.

Diurnal Variation and Effects of Dilation and Sedation on Intraocular Pressure in Infant Rhesus Monkeys

Krista M Beach  1 , Li-Fang Hung  1 , Linjiang Lou  1 , Lisa A Ostrin  1
Affiliations

Diurnal Variation and Effects of Dilation and Sedation on Intraocular Pressure in Infant Rhesus Monkeys

Krista M Beach et al. Curr Eye Res. 2023 Mar.

Abstract

Purpose: Intraocular pressure (IOP) is an important factor in numerous ocular conditions and research areas, including eye growth and myopia. In infant monkeys, IOP is typically measured under anesthesia. This study aimed to establish a method for awake IOP measurement in infant rhesus monkeys, determine diurnal variation, and assess the effects of dilation and sedation.

Methods: Awake IOP (iCare TonoVet) was measured every 2 h from 7:30 am to 5:30 pm to assess potential diurnal variations in infant rhesus monkeys (age 3 weeks, n = 11). The following day, and every 2 weeks to age 15 weeks, IOP was measured under three conditions: (1) awake, (2) awake and dilated (tropicamide 0.5%), and (3) sedated (ketamine and acepromazine) and dilated. Intraclass correlation coefficient (ICC) was used to determine intersession repeatability, and repeated measures. ANOVA was used to determine effects of age and condition.

Results: At age 3 weeks, mean (±SEM) awake IOP was 15.4 ± 0.6 and 15.2 ± 0.7 mmHg for right and left eyes, respectively (p=.59). The ICC between sessions was 0.63[-0.5 to 0.9], with a mean difference of 2.2 ± 0.3 mmHg. Diurnal IOP from 7:30 am to 5:30 pm showed no significant variation (p=.65). From 3 to 15 weeks of age, there was a significant effect of age (p=.01) and condition (p<.001). Across ages, IOP was 17.8 ± 0.7 mmHg while awake and undilated, 18.4 ± 0.2 mmHg awake and dilated, and 11.0 ± 0.3 mmHg after sedation and dilation.

Conclusions: Awake IOP measurement was feasible in young rhesus monkeys. No significant diurnal variations in IOP were observed between 7:30 am and 5:30 pm at age 3 weeks. In awake monkeys, IOP was slightly higher after mydriasis and considerably lower after sedation. Findings show that IOP under ketamine/acepromazine anesthesia is significantly different than awake IOP in young rhesus monkeys.

Keywords: Intraocular pressure; rebound tonometry; rhesus monkeys; sedation.

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Figures

Figure 1:
Figure 1:
Intraocular pressure (IOP) of the right eye (mean mmHg ± SEM) measured every two hours from 7:30 am to 5:30 pm in awake infant monkeys (n = 10)
Figure 2:
Figure 2:
Intraocular pressure (IOP) of the right eye (mean mmHg ± SEM) measured every two weeks in infant monkeys (n = 11) while awake and undilated (black symbols), awake and dilated (white symbols), and sedated and dilated (red symbols). A significant effect of condition was demonstrated (P<.001)
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