Magnetic resonance imaging in patients implanted with Ex-PRESS stainless steel glaucoma drainage microdevice

To evaluate whether artifacts caused by a stainless steel glaucoma drainage device can alter the interpretation of magnetic resonance imaging (MRI) scans of the optic nerve and brain.

Consecutive case series.

Five patients (7 eyes) with Ex-PRESS devices (Optonol Ltd, Neve Ilan, Israel) positioned at the limbus were studied. For each subject, an axial T1-weighted, axial and coronal T2-weighted with fat saturation, and whole brain proton density (PD)/T2-weighted MRI scan was obtained. Standard MRI protocol was not optimized for the imaging of patients harboring Ex-PRESS implants. The effects of the device on PD/T2 pulse sequence imaging of the optic nerve and brain were rated from 1 (optic nerve margins unidentifiable or brain details altered) to 5 (excellent visualization of the optic nerve and brain).

For optic nerve visualization, 1 optic nerve scored 2, 3 optic nerves scored 3, and 3 optic nerves scored 4 (mean, 3.3 +/- 0.8 standard deviation). For whole brain imaging, 4 patients scored 4 and 1 patient scored 5 (mean, 4.2 +/- 0.4 standard deviation).

Our data demonstrate that interpretation of MRI scans of the orbit and brain is unaffected by the artifacts caused by the Ex-PRESS shunt, whereas optic nerve imaging may be affected. We are unaware of previous reports of this finding and could find no reference to it in a computerized search using PubMed.