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T. Maleki, G. Chitnis, L. B. Cantor, B. Ziaie; Biodegradable Microfabricated Plug-Filters for Glaucoma Drainage Devices. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4424.
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To regulate the aqueous outflow, hence overcome the postoperativehypotony in non-valaved glaucoma drainage devices (GDD).
Batch fabricated biodegradable plug-filters were developed ina conical frustum shape. A 40µm in diameter hole was laser-drilledat the center of the plug to allow aqueous humor outflow throughthe plug.
Fig. 1 shows an optical image of the batch fabricated filtersin a polydimethylsioxane (PDMS) mold. SEM image of a filter,(height=500µm, lower base=500µm, upper base=300µm)is depicted in the insert. The filter was plugged into a GDD’stube and the flow rate versus pressure of the system was measured.
Fig. 2 shows the measurement results. The DI water flow rateat 17mmHg dropped from 716 µl/min in an open tube to 26µl/min in the plugged-tube. However, the flow resistanceof aqueous humor is 5-6 times that of DI water (Johnson et.al.,1986), hence its flow rate will be much lower. The biodegradableplug-filter dissolves within 3-4 weeks after shunt implantation,by which time the drainage plate is generally encapsulated withminimal risk of developing hypotony, and it will not affectthe long term fluid flow rate.
New filter-plug design minimizes the risk of postoperative hypotony.The batch compatible fabrication process and the resulting filterstructure simplify filter integration with commercially availableshunts.
Figure2: Measurement results showing a strong outflow regulation versusapplied pressure. Inset shows an optical picture of the plug-filterin a silicon tube
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