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Updated: Jun 21, 2026

Experimental Glaucoma Induced by Ocular Injection of Magnetic Microspheres
Published on: February 2, 2015
Is the Ex-PRESS glaucoma shunt magnetic resonance imaging safe?
Noa Geffen1, Graham E Trope, Tariq Alasbali
1Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada. noatal1122@gmail.com
Introduction:
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.
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