title: Performance of and Pressure Elevation Formed by Small-diameter Microtubes Used in Constant-flow Sets.
abstract: OBJECTIVE
  We explored the performance of and pressure elevation caused by small-diameter microtubes used to reduce overfiltration.
  
  
  METHODS
  Using a syringe pump-driven constant-flow setting (2 µL/min), pressures were measured for polytetrafluoroethylene (PTFE) microtubes 5 mm in length with inner diameters of 51, 64, and 76 µm and for polyether block amide (PEBAX) microtubes with an inner diameter of 76 µm. Experiments (using microtubes only) were initially performed in air, water, and enucleated pig eyes and were repeated under the same conditions using intraluminal 9/0 nylon stents.
  
  
  RESULTS
  The pressures measured in air in 51-, 64-, and 76-µm-diameter PTFE microtubes differed significantly (22.1, 16.9, and 12.2 mmHg, respectively; p < 0.001), and that of the 76-µm-diameter PEBAX microtube was 15.8 mmHg (p < 0.001 compared to the 12.2 mmHg of the 76-µm-diameter PTFE microtube). The pressures measured in water also differed significantly among the three microtubes at 3.9, 3.0, and 1.4 mmHg, respectively, while that in the PEBAX microtube was 2.6 mmHg (all p < 0.001). Using the intraluminal stent, the pressure in water of the three different PTFE microtubes increased to 22.6, 18.0, and 4.1 mmHg, respectively, and that in the PEBAX microtube increased to 10.5 mmHg (all p < 0.001). Similar trends were evident when measurements were performed in pig eyes.
  
  
  CONCLUSIONS
  Although microtubes of smaller diameter experienced higher pressure in air, reduction of the inner diameter to 51 µm did not adequately increase the pressure attained in water or pig eyes. Insertion of an intraluminal stent effectively elevated the latter pressures. PEBAX microtubes created higher pressures than did PTFE microtubes.
authors.affiliation: Department of Ophthalmology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea.
authors.forename: Sae Woon
authors.initials: SW
authors.lastname: Sohn
authors.affiliation: Department of Mechatronics Engineering, Chungnam National University, Daejeon, Korea.
authors.forename: Myounggyu D
authors.initials: MD
authors.lastname: Noh
authors.affiliation: Malgeunnoon Eye Clinic, Daejeon, Korea.
authors.forename: Jong-Hyun
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea.
authors.forename: Kyoung Nam
authors.initials: KN
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea.
authors.forename: Chang-Sik
authors.initials: CS
authors.lastname: Kim
authors.affiliation: Department of Ophthalmology, Kim's Eye Hospital, Konyang University College of Medicine, Seoul, Korea.
authors.forename: Byung Heon
authors.initials: BH
authors.lastname: Ahn
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D007429:Intraocular Pressure / Q000502:physiology*; D013508:Ophthalmologic Surgical Procedures / Q000295:instrumentation*; D011138:Polytetrafluoroethylene; D011474:Prosthesis Design; D013552:Swine
chemical_list: D011138:Polytetrafluoroethylene
keywords: Intraluminal stent; Intraocular pressure; Microtube; Polyether block amide; Polytetrafluoroethylene