Outflow facilities through descemets membrane in rabbits
D. Spiegel, M. Schefthaler, K. Kobuch
Purpose: The outflow pathway in viscocanalostomy, a new procedure in glaucoma surgery, is unclear, however outflow through Descemets membrane is discussed. This study evaluates outflow rates through Descemets membrane at different IOP levels in rabbits.
Methods: 51 Descemets membranes without endothelium from enucleated rabbit eyes where installed in a double ring system, the Minuthsheet. Different pressure levels (20,25,30,40,50 mmHg) were appointed to one side of the system. The system was filled with balanced salt solution. The total amount of fluid perculating through Descemets membrane was measured after 12 hours. Based on this flow-rates were calculated. The area of Descemets membrane was 6,9 mm2.
Results: At the level of 20 mmHg the flow-rate was less than 0.003µl/min. At pressure levels above 30 mmHg flow rates ranged from 0.04 to 0.15 µl/min. To achieve pressure control at high pressures at least an area of 150 mm2 of Descemets membrane would be needed.
Conclusions: Descemets membrane itself provides good outflow resistance in rabbit eyes. Based on our results for pressure control by outflow through Descemets membrane only, at least the whole corneal area is needed. If these findings apply to humans additional outflow soucres in cases of viscocanalostomy are necessary.
Klinik und Poliklinik für Augenheilkunde, der Universität Regensburg, Franz-Josef-Strauß-Allee 11, D-93047 Regensburg