Chapter 20 - Autoimmunity in visual loss

Abstract

There are a number of autoimmune disorders which can affect visual function. There are a very large number of mechanisms in the visual pathway which could potentially be the targets of autoimmune attack. In practice it is the retina and the anterior visual pathway (optic nerve and chiasm) that are recognised as being affected in autoimmune disorders. Multiple Sclerosis is one of the commonest causes of visual loss in young adults because of the frequency of attacks of optic neuritis in that condition, however the basis of the inflammation in Multiple Sclerosis and the confirmation of autoimmunity is lacking. The immune process is known to be highly unusual in that it is not systemic and confined to the CNS compartment. Previously an enigmatic partner to Multiple Sclerosis, Neuromyelitis Optica is now established to be autoimmune and two antibodies – to Aquaporin4 and to Myelin Oligodendrocyte Glycoprotein – have been implicated in the pathogenesis. The term Chronic Relapsing Inflammatory Optic Neuropathy is applied to those cases of optic neuritis which require long term immunosuppression and hence are presumed to be autoimmune but where no autoimmune pathogenesis has been confirmed. Optic neuritis occurring post-infection and post vaccination and conditions such as Systemic Lupus Erythematosus and various vasculitides may cause direct autoimmune attack to visual structures or indirect damage through occlusive vasculopathy. Chronic granulomatous disorders such as Sarcoidosis affect vision commonly by a variety of mechanisms, whether and how these are placed in the autoimmune panoply is unknown. As far as the retina is concerned Cancer Associated Retinopathy and Melanoma Associated Retinopathy are well characterised clinically but a candidate autoantibody (recoverin) is only described in the former disorder. Other, usually monophasic, focal retinal inflammatory disorders (Idiopathic Big Blind Spot Syndrome, Acute Zonal Occult Outer Retinopathy and Acute Macular Neuroretinitis) are of obscure pathogenesis but an autoimmune disorder of the post-infectious type is plausible. Visual loss in autoimmunity is an expanding field: the most significant advances in research have resulted from taking a well characterised phenotype and making educated guesses at the possible molecular targets of autoimmune attack.