Insights into Current Management Strategies for Dysthyroid Optic Neuropathy: A Review

Dysthyroid optic neuropathy (DON) is a potentially sight-threatening eye disease associated with Graves' orbitopathy (GO). DON is not common in GO patients, reportedly occurring in only about 5% of patients. The pathogenesis of severe DON is considered to involve both muscular nerve strangulation and impaired blood flow. There is some objective grading of physical examination findings and the severity of GO, including a clinical activity score (CAS) and EUropean Group On Graves' Orbitopathy (EUGOGO), but no specialized protocol completely characterizes DON. Most clinicians have decided that the combination of clinical activity findings, including visual acuity, color vision, and central critical fusion frequency, and radiological findings, including magnetic resonance imaging (MRI), can be used to diagnose DON. MRI has the most useful findings, with T2-weighted and fat-suppressed images using short-tau inversion recovery (STIR) sequences enabling detection of extraocular changes including muscle and/orbital fat tissue swelling and inflammation and, therefore, disease activity. The first-choice treatment for DON is intravenous administration of steroids, with or without radiotherapy. Unfortunately, refractoriness to this medical treatment may indicate the need for immediate orbital decompression within 2 weeks. Especially in the acute phase of DON, thyroid function is often unstable, and the surgeon must always assume the risk of general anesthesia and intra- and post-operative management. In addition, there are currently many possible therapeutic options, including molecular-targeted drugs. The early introduction and combination of these immunomodulators, including Janus kinase inhibitors and insulin-like growth factor-1 receptor antibody (teprotumumab), may be effective for GO with DON. However, this is still under investigation, and the number of case reports is small. It is possible that these options could reduce systemic adverse events due to unfocused glucocorticoid administration. The pathophysiology of DON is not yet fully understood, and further studies of its treatment and long-term visual function prognosis are needed.