Characterization of Episcleral Venous Pressure in Humans

Measurement of episcleral venous pressure is critical to understanding the changes in intraocular pressure that occur in normal and glaucomatous eyes, but no reliable method has previously been available for human use, resulting in an incomplete understanding of aqueous humor dynamics. We have developed a new technique and device to allow precise and accurate measurement of episcleral venous pressure by providing reproducible measurement endpoints. In this project, we further develop the technique and analysis software so that it is suitable for large scale projects, enabling future investigations into episcleral venous pressure and aqueous humor dynamics in normal subjects and glaucoma patients.

Elevated pressure in the eye is the most important risk factor for glaucoma, and lowering of eye pressure is currently the only effective treatment. The pressure in the veins of the eye (episcleral venous pressure) is an important determinant of eye pressure. However, little is known about episcleral venous pressure because of inadequate measurement techniques. As a result, our understanding of eye pressure, the causes of glaucoma, and therapies for glaucoma, is incomplete.

We have recently developed a new way of measuring episcleral venous pressure. Unlike previous techniques and devices, it does not allow for subjective judgments, and therefore can provide more reliable readings. However, the technique is currently very labor intensive due to the large amount of data that is collected and is not suitable for large projects. Our goal is to improve and automate the device and software so that episcleral venous pressure can be reliably measured in larger projects.

To do this, we plan to find the features of episcleral veins that provide the most reliable measurements and then automate the analysis of data to provide rapid measurements of pressure. We will also measure episcleral venous pressure in normal subjects to test the software and begin the process of documenting the range of normal values.

No new technique for episcleral venous pressure measurement has been developed in over two decades, and our technique is the first objective measurement suitable for human use. This project utilizes custom-designed equipment and state-of-the-art image analysis techniques, combined with clinical measurements. When completed, this work will enable future research into the regulation of eye pressure, causes of glaucoma, and treatments for glaucoma.