Abstract
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.