September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Flow Rates in Baerveldt Glaucoma Implants with 3-0, 4-0, and 5-0 Stents, as a Function of Pressure: a Laboratory Study.
Author Affiliations & Notes
  • Roshni Uday Ranjit
    Ophthalmology, University of South Florida, Tampa, Florida, United States
  • Maximillian Padilla
    Ophthalmology, University of South Florida, Tampa, Florida, United States
  • Mark Disclafani
    Ophthalmology, University of South Florida, Tampa, Florida, United States
  • David W Richards
    Ophthalmology, University of South Florida, Tampa, Florida, United States
  • Footnotes
    Commercial Relationships   Roshni Ranjit, None; Maximillian Padilla, None; Mark Disclafani, None; David Richards, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 5624. doi:
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      Roshni Uday Ranjit, Maximillian Padilla, Mark Disclafani, David W Richards; Flow Rates in Baerveldt Glaucoma Implants with 3-0, 4-0, and 5-0 Stents, as a Function of Pressure: a Laboratory Study.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5624.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To determine optimum stent diameter for immediate post-operative pressure control using a Baerveldt glaucoma drainage device (GDD), when the stent method is used at the time of implantation of these non-valved devices. We are not aware of any such previous laboratory study, even though stents of multiple diameters are commonly used clinically as “ripcords”.

Methods : Laboratory setup included a custom model eye (University of South Florida Invention Disclosure, M. DiSclafani,2015), with a clear corneal cap, which was made to be water-tight with independent water-tight connections using a source of balanced salt solution (BSS, at controlled elevation), a digital manometer (Dwyer Instruments Model 490A-1), and the silicone tubing (inner diameter 300 microns) of a Baerveldt 350 GDD. Height of the BSS source was controlled to create pressures ranging from 0 to 50 mm Hg in the model eye. Flow rates were measured though the GDD tubing as the tubing was either unblocked or partially occluded by 3-0 (diameter 200 microns), 4-0 (150 u) and 5-0 (100 u) Nylon suture segments. GDD plate (with tube connection) was left uncovered and unobstructed; resistance due to Tenon’s capsule and/or conjunctiva, as expected clinically, was therefore not accounted for.

Results : Flow rates increased with pressure and decreased with increasing diameter of the stent. Flow rate differences for 10 mmHg changes in pressure were statistically significant at the p<0.01 level (Student’s T test). For the most occlusive stent (3-0 Nylon), flow rates at pressures of 10, 20, and 30 mm Hg were typically about 90, 125, and 400 microliters(ul)/min, respectively.

Conclusions : Unobstructed inner cross-sectional area of the GDD tube, as tested, is reduced to 0.56 of normal for the 3-0 stent, 0.75 for the 4-0, and 0.89 for the 5-0. In our laboratory study, none of these reductions was sufficient to reduce flow (at clinically expected pressures) to the normal baseline rate of 2.75 +/- 0.63 ul/min. Additional studies are warranted to develop stenting procedures to avoid immediate postoperative hypotony with these GDD's.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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