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research-article

Validation of an Experimental Setup to Reliably Simulate Flow through Non-Valved Glaucoma Drainage Devices

[+] Author and Article Information
Tabitha H.T. Teo

Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, 3138 Learned Hall, Lawrence, KS 66045
tabithateo55@gmail.com

Ajay Ramani

Aerotek, 800 Tower Dr., Suite 700, Troy, MI 48098
logontoajay@gmail.com

Paul Munden

Oklahoma City VA Health Care System, 921 NE 13th Street, Oklahoma City, OK 73104
paul.munden@va.gov

Sara Wilson

ASME Fellow, Human Motion Control Laboratory, Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, 3138 Learned Hall, Lawrence, KS 66045
sewilson@ku.edu

Sarah Kieweg

ASME Member, Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, 3138 Learned Hall, Lawrence, KS 66045
sarah.kieweg@gmail.com

Dr. Ronald L. Dougherty

Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, 3138 Learned Hall, Lawrence, KS 66045
doughrty@ku.edu

1Corresponding author.

ASME doi:10.1115/1.4040498 History: Received February 12, 2018; Revised June 04, 2018

Abstract

Treatment of vision-threating elevated intraocular pressure (IOP) for severe glaucoma may require glaucoma drainage device (GDD) implantation to shunt aqueous humor from the eye's anterior chamber and lower IOP to acceptable levels of 8-21 mm Hg. Non-valved GDDs (NVGDDs) cannot maintain IOP in that acceptable range during the early post-operative period; and require intra-operative modifications during the first 30 days after surgery. Other GDDs have valves to overcome this issue, but are less successful with maintaining long-term IOP. Our research goal is to improve NVGDD post-operative performance. Little rigorous research has been done to systematically analyze NVGDDs flow/pressure characteristics. We describe a system developed to assess the pressure drop for physiologic flow rates through NVGDD-like microtubes of various lengths/diameters. Experimental pressures for flow through hollow microtubes are near predictive theory's lower limit. A 50.4 micron inner diameter microtube yields a 35.1 mm Hg experimental pressure, while theory predicts 35.6-55.5 mm Hg. An annular example, 358.8 micron outside and 330.7 micron inside diameters, yields a 9.6 mm Hg experimental pressure, within theoretical predictions of 4.2-19.2 mm Hg. These results are repeatably consistent over 25 days, which fits the 20-35 day period needed for scar tissue formation to achieve long-term IOP control. Future efforts will use this validated experimental setup, corroborated by theory, to study the performance of various insert sizes, dissolving inserts, and drug eluding inserts.

Copyright (c) 2018 by ASME
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