February 2013 Online Photo Diagnosis

By William Townsend, OD, FAAO

Corneal Neovascularization Secondary to Chronic Orbital Congestion Associated with Thyroid Ophthalmopathy

The individual in this photo is a 57-year-old male who suffered from long-standing Grave's Disease with ophthalmopathy and associated complications including exophthalmos, exposure keratitis, and corneal neovascularization. When he initially presented to our office, he had been a long-term cigarette smoker. Cigarette smokers have a seven-times higher risk for developing Graves' disease, and smokers have a much higher risk for developing ophthalmopathy associated with Grave's disease. We had persuaded the patient to discontinue smoking, but his ophthalmopathy continued to progress. He developed orbital congestion, severe proptosis, and increased intraocular pressure; all of these findings were secondary to edema of the extraocular muscles and orbital tissue. Progressive proptosis prohibited closure of his eyelids; that in turn led to severe exposure keratitis and ultimately to corneal neovascularization.

Grave's orbitopathy is caused by autoantibodies that bind to the thyrotropin receptor on thyroid follicular cells and stimulate uncontrolled production of thyroid hormones. Many of the signs and symptoms of Graves' ophthalmopathy arise from enlargement of muscle and adipose tissue in the bony cavity. The underlying pathology results from activation of quiescent fibroblasts by autoantibodies. Fibroblasts secrete hyaluronan, a glycosaminoglycan found in most connective tissue as well as in vitreous. Hyaluronan absorbs large amounts of water, leading to swelling of the extraocular muscles and adipose tissue. The resulting increase in the orbital content volume increases pressure within the orbit, often leading to proptosis and esophthalmos.

In this patient's case, we noted increasing intraocular pressures that required prescribing of an ocular hypertensive agent. We ordered CT scans of the orbits, which confirmed edema and generalized congestion of the soft orbital tissue. We referred the patient to an orbital/plastic surgeon for evaluation and possible decompressive surgery.

Complications of Grave's orbitopathy include diplopia, compressive neuropathy of the optic nerve, and increased intraocular pressure, especially in up gaze. Management includes smoking cessation, thyroid gland ablation, and orbital decompression. The goal of surgery is to reduce intraorbital congestion and hence, to relieve or lessen the impact of orbital congestion on structures located within the orbits.

References:

Bahn RS. Graves' Ophthalmopathy. N Engl J Med 2010; 362:726-738 February 25, 2010

Siracuse-Lee DE, Kazim M. Orbital decompression: current concepts. Curr Opin Ophthalmol. 2002 Oct;13(5):310-6.

Khoo TK, Bahn RS. Pathogenesis of Graves' ophthalmopathy: the role of autoantibodies Thyroid. 2007 Oct;17(10):1013-8.

Weetman AP, McGregor AM. Autoimmune thyroid disease: further developments in our understanding. Endocr Rev. 1994 Dec;15(6):788-830.