MEASUREMENT OF THE HYDRAULIC CONDUCTIVITY OF THE VITREOUS HUMOR

The hydraulic conductivity of the vitreous humor has been measured for the bovine eye. The experiment was carried out by placing the vitreous within an upright cylindrical chamber, open at both ends, and letting its liquid content drain out of the bottom opening by gravity through a 20-μm nylon mesh filter. Additional negative pressure was provided at the exit by a hanging drainage tube. The diminishing vitreous volume was measured in terms of the height in the chamber and recorded as a function of time. The reduction in the vitreous liquid content also caused the hydraulic conductivity to reduce, and this parameter was quantified on the basis of previously developed theories of fibrous porous media that have been very well established. A theoretical model with a fully analytical expression for the vitreous volume undergoing drainage was developed and used as a least-squares best fit to deliver the initial hydraulic conductivity value of K0/μ = (7.8 ± 3.1) × 10-12 m2/(Pa s). The measurements were made with the hyaloid membrane intact and therefore represent an effective conductivity for the entire system, including possible variations within the vitreous.