title: Polymeric check valve with an elevated pedestal for precise cracking pressure in a glaucoma drainage device.
abstract: This paper presents the design, fabrication, and characterization of a polymeric micro check valve for a glaucoma drainage device (GDD) featuring the precise regulation of intraocular pressure (IOP) and effective aqueous humor turnover (AHT). The pedestal, slightly elevated by selective coating of a parylene C film, induces pre-stress in the thin valve membrane, which enhances the predictability of the cracking pressure of the GDD. The proposed GDD comprises a cannula and a normally closed polymeric micro check valve, which are made of PDMS, a biocompatible polymer, with three layers: top (cover), intermediate (thin valve membrane), and bottom (base plate). A feedback channel, located between the top and intermediate layers, prevents reverse flow by feeding the pressure of the outlet channel back to the thin valve membrane. To achieve a precise cracking pressure and sufficient drainage of humor for humans, the thicknesses of the valve membrane and parylene C film are designed to be 58 μm and 1 μm, respectively, which are confirmed using a COMSOL simulation. The experimental results show that the cracking pressure of the fabricated GDD lies within the range of normal IOP (1.33-2.67 kPa). The forward flow rate (drainage rate), 4.3 ± 0.9 μL/min at 2.5 kPa, is adequate to accommodate the rate of AHT in a normal human eye (2.4 ± 0.6 μL/min). The reverse flow was not observed when a hydrostatic pressure of up to 4 kPa was applied to the outlet and the feedback channel.
authors: Department of Medical System Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors: Chang-Ju
authors: CJ
authors: Park
authors: Department of Medical System Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors: Dong-Seong
authors: DS
authors: Yang
authors: Department of Medical System Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors: Jung-Joon
authors: JJ
authors: Cha
authors: Department of Medical System Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea. jonghyun@gist.ac.kr.
authors: Jong-Hyun
authors: JH
authors: Lee
mesh_terms: D005901:Glaucoma; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure; D011474:Prosthesis Design
keywords: Aqueous humor; Feedback channel; Glaucoma drainage device; Micro check valve; Parylene C film; Pre-stress