title: Is the Ex-PRESS glaucoma shunt magnetic resonance imaging safe?
abstract: BACKGROUND
  Ex-PRESS mini glaucoma shunt is a miniature, stainless steel, nonvalved device used for the treatment of glaucoma. The purpose of this study was to evaluate the safety of the Ex-PRESS glaucoma shunt during magnetic resonance (MR) imaging.
  
  
  METHODS
  The effect of a magnetic field on the Ex-PRESS glaucoma shunt was evaluated in 4 scenarios. (1) Wet dish test: the device was placed floating in a dish filled with water and exposed to magnetic fields of 1.5 and 3 Tesla for 30 seconds. (2) Dry dish test: the device was placed on a dry dish and exposed to a magnetic field of 3 Tesla MR for 30 seconds. (3) Intracameral test: the device was floating freely in the anterior chamber of a human cadaver eye and was exposed to a magnetic field of 3 Tesla MR. (4) Scleral fixation test: the device was implanted through the sclera of a human cadaver eye and was exposed to a magnetic field of 3 Tesla MR.
  
  
  RESULTS
  During the wet dish test the Ex-PRESS glaucoma shunt immediately moved across the dish with both 1.5 and 3 Tesla MR. No movements were noted during the dry dish test, intracameral test, or the scleral fixation test.
  
  
  CONCLUSIONS
  Although the Ex-PRESS glaucoma shunt is influenced by magnetic field forces, it is likely MR of up to 3 Tesla is safe due to resistance provided by the ocular tissue.
authors: Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada. noatal1122@gmail.com
authors: Noa
authors: N
authors: Geffen
authors: Graham E
authors: GE
authors: Trope
authors: Tariq
authors: T
authors: Alasbali
authors: David
authors: D
authors: Salonen
authors: Adrian P
authors: AP
authors: Crowley
authors: Yvonne M
authors: YM
authors: Buys
mesh_terms: D001082:Aqueous Humor / Q000378:metabolism; D004574:Electromagnetic Fields; D004869:Equipment Safety; D020327:Glaucoma Drainage Implants; D006801:Humans; D008279:Magnetic Resonance Imaging; D013193:Stainless Steel
chemical_list: D013193:Stainless Steel