Is the Ex-PRESS glaucoma shunt magnetic resonance imaging safe?
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.
Geffen
Noa
N
Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada. noatal1122@gmail.com
Trope
Graham E
GE
Alasbali
Tariq
T
Salonen
David
D
Crowley
Adrian P
AP
Buys
Yvonne M
YM
D001082:Aqueous Humor / Q000378:metabolism; D004574:Electromagnetic Fields; D004869:Equipment Safety; D020327:Glaucoma Drainage Implants; D006801:Humans; D008279:Magnetic Resonance Imaging; D013193:Stainless Steel
D013193:Stainless Steel