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C. Dozier, R.R. Allingham, S. Asrani, Y. Kondo, F.C. Decroos, K.C. Olbrich, B. Klitzman; Quantifying Outflow Resistance of a Modified Glaucoma Valve in vivo . Invest. Ophthalmol. Vis. Sci. 2006;47(13):32.
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© ARVO (1962-2015); The Authors (2016-present)
Many glaucoma patients benefit from implantation of a valved drainage device. However, the current implants induce the formation of a thick fibrous capsule that increases outflow resistance and thus control of intraocular pressure (IOP). We hypothesize that a glaucoma implant constructed of a porous polymer material will result in an altered healing response that will reduce the outflow resistance of the device, which will result in improved IOP control over conventional implants. The purpose of this study was to quantify the effects of a porous polymer on the outflow resistance of a valved glaucoma drainage device.
A control implant was placed into one eye and an identical implant covered by porous material (experimental implant) was placed into the contralateral eye of ten New Zealand rabbits. After ten weeks, the anterior chamber tubes were cannulated in situ and perfused with saline at a flow rate (Q) of 2 µL/min for 30 min followed by perfusion at a flow rate of 5 µL/min for 30 min. During perfusion, the hydrostatic pressure (P) within the device was measured and the outflow resistance (R) was calculated as R=P/Q.
At a flow rate of 2 µL/min, the average outflow resistance of the experimental implant was 15.5 ± 1.8 mmHg/µL/min, while the average outflow resistance of the control valve was 24.1 ± 2.2 mmHg/µL/min (p <0.001). At a flow rate of 5 µL/min, the average outflow resistance of the experimental implant was 7.1 ± 0.9 mmHg/µL/min, while the average outflow resistance of the control valve was 10.2 ± 1.1 mmHg/µL/min (p <0.05).
We have found that modification of a valved implant using a porous polymer significantly reduces outflow resistance compared to a standard valved device.
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