Abstract
Purpose :
The aim of this experiment is to measure the hydraulic permeability of water through the bovine vitreous humor and hyaloid membrane using a diffusion chamber.
Methods :
A plexiglass diffusion chamber similar to the Ussing chamber was specially fabricated to hold the entire bovine vitreous humor. The insert in this case was a 3 cm thick plexiglass block with a 24 mm circular hole to hold the vitreous. The vitreous humor was extracted from fresh bovine eyes (source: Manning Beef, Pico Rivera, CA) with the hyaloid membrane intact, and carefully placed in the insert and held in place with 100 micron filters to cover each side of the hole. The system was then assembled using O-ring seals and held in an Ussing chamber rack. Water (0.9% saline solution) was fed into the left chamber under gravitational pressure (120 cm pressure head), all bubbles in the system were cleared. The water that crossed the vitreous to the other side was collected after 17 hours.
Results :
In this preliminary experiment 34 ml of water was collected. With the vitreous in a cylindrical chamber of cross-section area of 13.57 cm2 and horizontal travel path of 3 cm, under a pressure of 120 cm of water, the hydraulic permeability was found to be 3.1 X 10-8 cm2/Pa-s. This is somewhat comparable to the result of Fatt [1] (9 ± 3 X 10-8 cm2/Pa-s) but quite a bit lower than Xu et al [2] who found (8.4 ± 4.5 X 10-7 cm2/Pa-s). More data are needed for accurate measurement. Besides, we have kept the hyaloid membrane intact which quite possibly offers more resistance. Taking the result of Xu et al as valid, we can carry out a resistance based calculation, subtract the vitreous-only resistance and end up with the resistance of the hyaloid on the two sides of the cell. This yields the hyaloid permeability as 2.17 X 10-8 cm/Pa-s.
Conclusions :
We have devised a system that measures the net permeability across the vitreous humor with the hyaloid membrane intact. While the data on the vitreous hydraulic permeability are not abundant, we can utilize the available results, combine with the current work and obtain the hyaloid membrane permeability.
References:
[1] I. Fatt and B. Hedbys, "Flow of water in the sclera," Exp. Eye Res., vol. 10, p. 243–249, 1970.
[2] J. Xu, J. J. Heys, V. H. Baroccas and T. W. Randolph, "Permeability and Diffusion in Vitreous Humor: Implications for Drug Delivery," Pharmaceutical Research,, vol. 17, no. 6, pp. 664-669, 2000.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.