Diagnostic differences in visual field defects Demyelinating versus compressive optic neuropathy

Abstract

In view of probable differences in the mechanism by which intrinsic and compressive lesions impair conduction in the optic nerves, we attempted to identify corresponding differences in the pattern of visual loss caused by demyelinating disease and a variety of compressive lesions in 69 visual fields of 59 patients. We found that immediately after onset of symptoms of acute optic neuritis a central scotoma is common (61%). But six months or more after the first visual symptoms, most visual defects (64%) caused by demyelinating disease are no longer detectable by the usual kinetic perimetric test stimuli. This high percentage of normal fields aids the separation of these patients from those with compressive lesions, all of whom have abnormal fields. We found that most compressive lesions caused uniform or irregular constriction of all isopters of the visual fields rather than scotomas. This observation suggests that compressive lesions reduce sensitivity in the visual field both centrally and peripherally by impairing conduction uniformly over the entire cross-section of the optic nerves. Another useful diagnostic finding was that, in contrast to only a minority of chronic demyelinating lesions, all compressive lesions reduced visual acuity.

Key Words:

• optic nerve
• visual fields
• multiple sclerosis
• optic neuritis