title: A novel implantable glaucoma valve using ferrofluid.
abstract: OBJECTIVE
  To present a novel design of an implantable glaucoma valve based on ferrofluidic nanoparticles and to compare it with a well-established FDA approved valve.
  
  
  METHODS
  Massachusetts Eye & Ear Infirmary, Boston, USA.
  
  
  METHODS
  A glaucoma valve was designed using soft lithography techniques utilizing a water-immiscible magnetic fluid (ferrofluid) as a pressure-sensitive barrier to aqueous flow. Two rare earth micro magnets were used to calibrate the opening and closing pressure. In-vitro flow measurements were performed to characterize the valve and to compare it to Ahmed™ glaucoma valve. The reliability and predictability of the new valve was verified by pressure/flow measurements over a period of three months and X-ray diffraction (XRD) analysis over a period of eight weeks. In vivo assessment was performed in three rabbits.
  
  
  RESULTS
  In the in vitro experiments, the opening and closing pressures of the valve were 10 and 7 mmHg, respectively. The measured flow/pressure response was linearly proportional and reproducible over a period of three months (1.8 µl/min at 12 mmHg; 4.3 µl/min at 16 mmHg; 7.6 µl/min at 21 mmHg). X-ray diffraction analysis did not show oxidization of the ferrofluid when exposed to water or air. Preliminary in vivo results suggest that the valve is biocompatible and can control the intraocular pressure in rabbits.
  
  
  CONCLUSIONS
  The proposed valve utilizes ferrofluid as passive, tunable constriction element to provide highly predictable opening and closing pressures while maintaining ocular tone. The ferrofluid maintained its magnetic properties in the aqueous environment and provided linear flow to pressure response. Our in-vitro tests showed reliable and reproducible results over a study period of three months. Preliminary in-vivo results were very promising and currently more thorough investigation of this device is underway.
authors.affiliation: Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, United States of America. Eleftherios_paschalis@meei.harvard.edu
authors.forename: Eleftherios I
authors.initials: EI
authors.lastname: Paschalis
authors.forename: James
authors.initials: J
authors.lastname: Chodosh
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Sperling
authors.forename: Borja
authors.initials: B
authors.lastname: Salvador-Culla
authors.forename: Claes
authors.initials: C
authors.lastname: Dohlman
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000502:physiology; D002138:Calibration; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D007429:Intraocular Pressure; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D008297:Male; D008422:Materials Testing; D011817:Rabbits; D014961:X-Ray Diffraction
chemical_list: D058185:Magnetite Nanoparticles