Visual Impairments

Abstract

Most patients referred to neurology service for visual disturbances have a chief complaint of blurred vision, double vision, or acute loss of vision. The visual symptoms may be either a positive or a negative phenomenon.

Positive phenomena includes the perception of light flashes, bright spots, scintillating scotomas, photopsia, phosphenes, and zigzag lines starting small and enlarging with fortifications (fortification spectra). These are usually seen in patients with migraine or epilepsy. Negative phenomena comprise blindness, visual field deficits or scotomas, decreased visual acuity, and color blindness or desaturation. These are usually seen in conditions like stroke, multiple sclerosis, and neuromyelitis optica.

Patients are usually hemodynamically stable. The history should provide details on the time of onset and the course of progression in addition to details of the type of visual phenomena experienced. The monocular or binocular nature of the symptoms and association with painful eye movements, diplopia, ptosis, bulbar dysfunction, jaw or tongue claudication, and constitutional symptoms are helpful in narrowing the differential diagnosis. The corresponding clinical signs should be sought in the physical examination which should also include ophthalmoscopy, visual acuity, and color vision testing.

Investigations may include CBC, ESR, CRP, TSH, PT, INR, fasting lipid profile, serum glucose, and HbA1c. Depending upon the underlying cause suspected, brain MRI and MRA, carotid ultrasound, 2-D echocardiogram, and EEG may be done. If optic neuritis is suspected, may order a visual evoked potential (VEP) study. If myasthenia gravis is being considered, may need acetylcholine receptor antibodies, repetitive nerve stimulation testing (+/− single-fiber EMG), and CT scan of the chest. Neuro-ophthalmology referral may be required. Treatment is specific to the underlying cause identified.