Defining the role of neuroimaging in normal-tension glaucoma

San Francisco - Debate continues over whether to perform neuroimaging in patients with typical normal-tension glaucoma (NTG), but there are warning signs that should prompt ordering magnetic resonance imaging (MRI) with gadolinium, said Christopher A. Girkin, MD, MPH, associate professor of ophthalmology and director, glaucoma service, Callahan Eye Foundation Hospital, University of Alabama at Birmingham.

Although results of several studies could not establish a cost benefit for routine imaging, in a trial reported by Ahmed et al. in 2002, cranial MRI revealed significant lesions compressing the anterior visual pathway in 4 of 62 patients with NTG versus none of 70 patients with primary open-angle glaucoma.

“Those results were somewhat surprising, but overall it seems neuroimaging in routine cases has low yield and questionable benefit so that further workup should focus only on cases that are atypical and vision-threatening,” Dr. Girkin said.

There are several signs of nonglaucomatous neuropathy that signal a need for further workup. Those consist of visual field loss that is out of proportion to optic disc changes; rim pallor greater in extent than the degree of cupping; central vision loss; color vision defect; vertically aligned visual field defects; neurologic fields that respect the vertical meridian; other cranial neuropathies; and a relative afferent pupillary defect that does not correspond to the degree of asymmetry in the visual field.