Disorders of vision in multiple sclerosis

Multiple sclerosis (MS) is a neurological inflammatory disorder known to attack the heavily myelinated regions of the nervous system including the optic nerves, cerebellum, brainstem and spinal cord. This review will discuss the clinical manifestations and investigations for MS and other similar neurological inflammatory disorders affecting vision, as well as the effects of MS treatments on vision. Assessment of visual pathways is critical, considering MS can involve multiple components of the visual pathway, including optic nerves, uvea, retina and occipital cortex. Optical coherence tomography is increasingly being recognised as a highly sensitive tool in detecting subclinical optic nerve changes. Magnetic resonance imaging (MRI) is critical in MS diagnosis and in predicting long-term disability. Optic neuritis in MS involves unilateral vision loss, with characteristic pain on eye movement. The visual loss in neuromyelitis optica spectrum disorder tends to be more severe with preferential altitudinal field loss, chiasmal and tract lesions are also more common. Other differential diagnoses include chronic relapsing inflammatory optic neuropathy and giant cell arteritis. Leber's hereditary optic neuropathy affects young males and visual loss tends to be painless and subacute, typically involving both optic nerves. MS lesions in the vestibulocerebellum, brainstem, thalamus and basal ganglia may lead to abnormalities of gaze, saccades, pursuit and nystagmus which can be identified on eye examination. Medial longitudinal fasciculus lesions can cause another frequent presentation of MS, internuclear ophthalmoplegia, with failure of ipsilateral eye adduction and contralateral eye abduction nystagmus. Treatments for MS include high-dose corticosteroids for acute relapses and disease-modifying medications for relapse prevention. These therapies may also have adverse effects on vision, including central serous retinopathy with corticosteroid therapy and macular oedema with fingolimod.