Orbital Involvement in Autoimmune Disorders: Graves’ Disease
Autoimmune disorder with orbital involvement frequently associated with thy-roid dysfunction. Histologic examination reveals inflammatory infiltration of the orbital cavity.
Women are affected eight times as often as men. Sixty percent of all patients have hyperthyroidism. Ten per cent of patients with thy-roid disorders develop Graves’ disease during the course of their life.
Graves’ disease is the most frequent cause of both unilateral and bilateral exophthalmos.
The precise etiology of this autoimmune disorder is not clear. Histo-logic examination reveals lymphocytic infiltration of the orbital cavity. The ocular muscles are particularly severely affected. Fibrosis develops after the acute phase.
An autonomous adenoma of the thyroid gland is not associated with Graves’ disease. Some patients with Graves’ disease never exhibit any thyroid dysfunction during their entire life.
The onset of this generally painless disorder is usually betweenthe ages of 20 and 45. Patients complain of reddened dry eyes with a sensa-tion of pressure (symptoms of keratoconjunctivitis sicca) and of cosmetic problems. Ocular motility is also limited, and patients may experience double vision.
Cardinal symptoms includeexophthalmos,which is unilateral in only 10% of all cases, and eyelid changes that involve development of a characteristic eyelid sign (Table 15.3 and Fig. 15.3). Thicken-ing of the muscles (primarily the rectus inferior and medialis) and sub-sequent fibrosis lead to limited motility and double vision. Elevation is impaired; this can lead to false high values when measuring intraocularpressure with the gaze elevated.
The tentative clinical diagnosis of Graves’ disease is supported by thicken-ing of the extraocular muscles identified in ultrasound or CT studies (Fig. 15.4). The further diagnostic work-up requires the cooperation of an internist, endocrinologist, and radiologist.
Rarer clinical syndromes such as orbital tumors andorbital pseudotumors must be excluded.
The main principles in treating the disease in itsacute stageinclude management of the thyroid dysfunction, systemic cortisone (initially 60 – 100 mg of prednisone) and radiation therapy of the orbital cavity. Surgicaldecompression of the orbital cavity is indicated inrecurrent cases that do notrespond to treatment to avoid compressive optic neuropathy. Exposure ker-atitis (keratitis due to inability to close the eye) should be treated withartifi-cial tears or tarsorrhaphy (partial or complete suture closure of the upper andlower eyelid to shorten or close the palpebral fissure). In the postinflam-matory stage of the disease,eye muscle surgerymay be performed to correctstrabismus.
Visual acuity will remain good if treatment isinitiated promptly. In the postinflammatory phase, exophthalmos often per-sists despite the fact that the underlying disorder is well controlled.