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. 2025 Aug 1;66(11):44.
doi: 10.1167/iovs.66.11.44.

Relationship Between Diurnal Variations of Episcleral Venous Pressure and Intraocular Pressure

Arash Kazemi  1 , Uttio Roy Chowdhury  2 , Michael P Fautsch  1 , Thurein M Htoo  2 , Barbara M Wirostko  2   3 , David O Hodge  4 , Arthur J Sit  1
Affiliations

Relationship Between Diurnal Variations of Episcleral Venous Pressure and Intraocular Pressure

Arash Kazemi et al. Invest Ophthalmol Vis Sci. .

Abstract

Purpose: To investigate the diurnal variations of episcleral venous pressure (EVP) and its relationships with IOP, blood pressure, and heart rate in healthy and systemic hypertension subjects.

Methods: Twenty healthy adults and eight patients taking systemic antihypertensive medications were enrolled. IOP and EVP of both eyes, systolic and diastolic blood pressure (SBP and DBP), and heart rate (HR), were measured at five time points, every two hours from 8 AM to 4 PM. IOP was measured by pneumatonometry, and EVP was assessed using a computer-controlled episcleral venomanometer with video recording and image processing. Changes in measurements at each time point were compared with baseline (8 AM) by using generalized estimating equation models. Correlations between EVP and other variables were determined using linear regression analysis.

Results: EVP and IOP were highest in the early morning (8 AM) and lowest in the late afternoon (4 PM), with statistically significant changes (P < 0.05) across all time points compared to baseline in normotensive subjects. Changes in EVP and IOP were correlated at all time points. In treated systemic hypertensive subjects, similar trends were observed, with significant IOP and EVP correlations at multiple time points. No clear pattern of correlation was noted between EVP, SBP, DBP, and HR in all subjects.

Conclusions: IOP and EVP follow a diurnal rhythm with the highest values in the early morning, which gradually decrease throughout the day. The relationship between IOP and EVP suggests that reduction of EVP can be an important target for clinical regulation and stability of IOP.

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Conflict of interest statement

Disclosure: A. Kazemi, None; U. Roy Chowdhury, Qlaris Bio, Inc. (E); M.P. Fautsch, Qlaris Bio, Inc. (O, C); T.M. Htoo, Qlaris Bio, Inc. (E); B.M. Wirostko, Qlaris Bio, Inc. (E); D.O. Hodge, None; A.J. Sit, Globe Biomedical, Inc. (C, I); Injectsense, Inc. (C, I); Nicox Ophthalmics, Inc. (F); PolyActiva, Pty (C); Qlaris Bio, Inc. (C, F); Santen Pharmaceuticals Asia, Pty (C)

Figures

Figure 1.
Figure 1.
Measuring episcleral venous pressure. (A) Computer controlled slit-lamp mounted episcleral venomanometer with fiber optic illumination. (B) An episcleral vein visualized through the slit-lamp with magnification ×25. (C) Changes in vessel brightness profile across an episcleral vein during episcleral venomanometry.
Figure 2.
Figure 2.
Individual diurnal IOP measurements for healthy and hypertension subjects. Each line represents measurements for one eye of one subject.
Figure 3.
Figure 3.
Individual diurnal EVP measurements for healthy and hypertension subjects. Each line represents measurements for one eye of one subject.
Figure 4.
Figure 4.
Diurnal changes of IOP (A) and EVP (B) showing significant correlation and similar downward trend across all time points throughout the day in healthy subjects. Error bars show standard error.
Figure 5.
Figure 5.
(A) Diurnal IOP and EVP changes (from 8 AM) in healthy subjects. (B) Correlation between IOP and EVP changes in healthy subjects. Each point represents the mean of three measurements taken at every time point for each subject.
Figure 6.
Figure 6.
Diurnal changes of IOP (A) and EVP (B) showing significant correlation and similar downward trend across most time points throughout the day in patients with systemic hypertension. Error bars show standard error.
Figure 7.
Figure 7.
(A) Diurnal IOP and EVP changes (from 8 AM) in systemic hypertension subjects. (B) Correlation between IOP and EVP changes in systemic hypertension subjects. Each point represents the mean of three measurements taken at every time point for each subject.
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