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Arthur J. Sit, Nitika Arora, Jay W. McLaren; Relationships between Episcleral Venous Pressure and Ocular and Systemic Variables in Healthy Subjects. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1959.
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Episcleral Venous Pressure (EVP) is an important determinant of intraocular pressure (IOP) according to the Goldmann equation. While previous studies have investigated the parameters that affect IOP, the parameters that affect EVP alone are poorly understood. In this study we examined the relationships between EVP and physiologic parameters including blood pressure, ocular, and systemic variables in healthy volunteers.
EVP was measured in 74 eyes of 37 healthy volunteers (ages: 46 to 80 years) by using a computerized, slitlamp mounted, episcleral venomanometer based on the pressure chamber technique. Venous pressure was assumed to be equal to the pressure in the chamber when the vein first began to collapse as the chamber was inflated at a constant rate. Age, central corneal thickness (CCT, by ultrasonic pachymetry), IOP, refractive error, height, weight, and blood pressure in the seated position were measured. Body mass index (BMI) was calculated. Correlations between EVP and these variables were examined by using generalized estimating equation models to account for the possible correlations between eyes from the same subjects.
In normal subjects, EVP is weakly correlated with refractive error, systolic and diastolic blood pressures, but is not correlated with the other variables that we measured. This relationship suggests that IOP may be affected by blood pressure through EVP. Changes in blood pressure must be considered when investigating the effects of systemic treatments on aqueous humor dynamics. The lack of a correlation between EVP and IOP suggests that other aqueous humor dynamics parameters are primarily responsible for the variations in IOP within healthy subjects.
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