Clinical Profile and Visual Outcomes after Treatment in Patients with Dysthyroid Optic Neuropathy

Patients with thyroid orbitopathy commonly present with soft tissue features of infiltrative disease, such as eyelid retraction and swelling, conjunctival injection, exophthalmos, and restrictive myopathy; however, in severe cases potentially blinding conditions, such as corneal ulcer and optic neuropathy, may manifest. Dysthyroid optic neuropathy (DON) occurs in approximately 5% of patients with thyroid orbitopathy [1]. DON patients may be asymptomatic with good vision, but it is best assessed by decreased visual acuity, reduced color vision, visual field defects, or afferent pupillary defects [2]. Most cases of DON are considered to occur as the result of optic nerve compression at the orbital apex via expanded intraorbital contents, particularly the extraocular muscles [1,3 9]. The increases in orbital fibroblast synthesis of hyaluronan result in an accumulation of glycosaminoglycan in the retrobulbar tissues [10]. The expansion of retrobulbar tissues in an area of fixed volume increases pressure at the orbital apex, which may inhibit axoplasmic flow [5] or induce optic nerve ischemia [8,11,12]. Treatments widely accepted for patients with DON include systemic corticosteroids, orbital radiation therapy and orbital decompression. Pulse methylprednisolone therapy may provide a rapid means for achieving maximal visual recovery, which can be sustained using a tapering regimen of oral corticosteroids and orbital irradiation [13]. Thyroid orbitopathy is characterized by an autoimmune active inflammation period of 6 to 18 months, during which, treatment with high-dose intravenous corticosteroids may effectively inhibit inflammatory processes and improve visual prognosis [14]. Radiation therapy is also useful in reducing active inflammation with optic nerve compression [5,7,10,15,16]. However, the efficacy of using radiation therapy alone must be determined, as the literature only reports on its utilization in combination with steroid therapy. Some authors have been unable to detect any beneficial effects of radiation therapy when used by itself [17,18]. Bony orbital decompression is considered to be the most effective treatment for DON, in that it provides rapid and persistent relief of apical compression [19]. As there remains controversy over the assessment and management of DON [20], it has proven difficult for clinicians to make an accurate diagnosis and recommend a particular measure to halt the progression of optic neuropathy and restore visual acuity. Asians have shown evidence of less severe orbitopathy than Caucasians, but a rather narrow orbital apex may result in earlier compressive features [2]. The principal objective of this study is to evaluate clinical pictures and treatment outcomes in Korean patients with DON. We have reviewed the clinical data and orbital imaging findings of 40 patients with DON who presented to the Samsung Medical Center, and evaluated the visual outcomes after treatment with intravenous steroids, orbital radiation therapy and/or orbital decompression.