Measurement of episcleral venous pressure

Episcleral venous pressure (EVP) is an important determinant of intraocular pressure (IOP) and can be measured by using various techniques. It has been measured non-invasively by estimating the pressure required to compress an episcleral vein to a predetermined endpoint. However, the lack of objective endpoints makes EVP measurement in humans uncertain, and a wide range of mean EVP has been reported in the literature. We review the evidence for physiologic regulation of EVP and its role in glaucoma therapy, techniques that have been used to measure EVP and the need for objective measurements, and reported values for EVP. We also review recent progress toward developing an objective technique for EVP measurement.

► Episcleral venous pressure is critical to understanding aqueous dynamics.
► Physiology suggests active regulation of episcleral venous pressure.
► History of episcleral venous pressure measurements techniques, limitations and recent advances.
► Episcleral venous pressure in normal subjects and glaucoma patients.
► Episcleral venous pressure changes with glaucoma medications.