Measuring Fluid Outflow in Rabbits Post Glaucoma Implant Surgery with iMvalv

FABIO A. GUARNIERI; RODRIGO TORRES

Denver

Conferencia; ARVO meeting; 2015

ARVO

Purpose: The iMvalv is an ocular implant with MEMS technology to produce aqueous humor drainage with an active mechanism. It was built with silicone multiple layers, for their plate and tube and has the capability of an active mechanism powered by a spiral antenna and a hybrid microcircuit. A first exploratory in-vivo implantation study in rabbits was performed and hydraulic conductivity was assessed in vivo and compared with in vitro testing.Methods: Four New Zeland male rabbits underwent insertion of a iMvalv implant into the anterior chamber of their right eyes. Left eyes were used as controls. Both eyes had outflow measurements performed at day 44 after surgery.Measurements were performed by cannulating the drainage tube ostium in situ with a needle attached to a fluid column at 10, 15, 20 and 25 mmHg. The drop in the fluid column was measured by a video camera. For the control eyes the anterior chamber of the unoperated fellow eye was cannulated with a needle attached to a fluid column. The drop in the fluid column was also measured. Then, Perkins tonometry was performed in order to calibrate previous measurements (pre and post surgery) with this fluid column pressure.Results: Perkins tonometry and manometric readings were compared in control eyes. Manometric readings of 10, 15, 20 and 25 mmHg gave mean values of 5, 6, 9 and 9.5 mmHg from simultaneous Perkins tonometries. In one implanted eye, a manometric column 20 mmHg was dropped to 11.4 mmHg and from 15 to 14.4 mmHg. In a second implanted eye the drop was from 21.6 to 21.1 mmHg. After euthanasia (day 50) conductivity of each valve was verified with a manometric column and a syringe pump concluding that one implant had still high conductivity while the other had low conductivity.Conclusions: We described a model to directly measure hydraulic conductivity in a rabbit glaucoma surgery implant with iMvalv and calibration of Perkins tonometry. The drainage of each implant can be reliably quantified and measured.