The Dysthyroid Optic Neuropathy

Graves’ orbitopathy—often known as Basedowian ophthalmopathy—is an autoimmune disorder that occurs in 5% of patients affected by the thyroid disease. Graves’ orbitopathy (GO) mainly affects retrobulbar soft tissue and it is the extra thyroidal manifestation of Graves’ disease and the most common cause of exophthalmos. The GO can have a major impact on the patient life, from both functional and aesthetic point of view; to some extent, it can be considered as an event deeply affecting the quality of life of the patients. The most serious consequence of GO is perhaps the dysthyroid optic neuropathy (DON), which is due to compression caused by the swelling of extraocular muscles and orbital fat. Many studies in the latest two centuries concentrated on GO and its treatments. Ocular changes associated with thyroid disease, in fact, have been described by Graves in 1835 and by Von Basedow in 1840, but they are likely to be observed and studied by Parry in 1786, who published posthumously a paper on GO in 1825. Despite ongoing advances in basic science and clinical research, the pathogenesis of GO is still unclear and highly effective therapeutic strategies remain elusive. The diagnosis of GO is mainly based on laboratory tests devoted to investigate thyroid dysfunction and/or autoimmunity. Recently, however, imaging approaches (among which we cite computed tomography, magnetic resonance imaging, ultrasound, and colour Doppler imaging) are increasingly adopted both in the diagnosis stage and in the follow-up, after proper clinical or surgical treatments have been applied. Imaging techniques, in particular, are relevant to spot morphological abnormalities affecting the orbital structures as well as to classify early stages of the diseases. In addition, imaging techniques are useful to identify those patients who are likely to get affected from DON in advance; such knowledge is crucial for an early treatment, and on the long run, it is effective in avoiding visual loss. This chapter mainly focuses on DON, and it aims at illustrating the most recent advances in its diagnosis and treatment. The chapter is structured as follows: we introduce the Graves’ orbitopathy, and then, we detail the main features of DON as well as the diagnostic procedures usually followed in clinical practice.