Orbital Involvement in Autoimmune Disorders Graves Disease

Definition

Autoimmune disorder with orbital involvement frequently associated with thyroid dysfunction. Histologic examination reveals inflammatory infiltration of the orbital cavity.

Epidemiology: Women are affected eight times as often as men. Sixty per cent of all patients have hyperthyroidism. Ten per cent of patients with thyroid disorders develop Graves' disease during the course of their life.

Graves' disease is the most frequent cause of both unilateral and bilateral exophthalmos.

Etiology: The precise etiology of this autoimmune disorder is not clear. Histologic examination reveals lymphocytic infiltration of the orbital cavity. The ocular muscles are particularly severely affected. Fibrosis develops after the acute phase.

H 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.

Symptoms: The onset of this generally painless disorder is usually between the ages of 20 and 45. Patients complain of reddened dry eyes with a sensation of pressure (symptoms of keratoconjunctivitis sicca) and of cosmetic problems. Ocular motility is also limited, and patients may experience double vision.

Diagnostic considerations: Cardinal symptoms include exophthalmos, 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). Thickening of the muscles (primarily the rectus inferior and medialis) and subsequent fibrosis lead to limited motility and double vision. Elevation is impaired; this can lead to false high values when measuring intraocular pressure with the gaze elevated.

Table 15.3 Eyelid signs in Graves' disease

Eyelid sign

Explanation

❖ Dalrymple's sign

Upper eyelid is retracted with visible sclera superior to the limbus and widened palpebral fissure with developing exposure keratitis (overactive muscle of Müller).

❖ von Graefe's sign

Upper eyelid retracts when the eye depresses (overactive muscle of Müller).

❖ Gifford's sign

Upper eyelid is difficult to evert (due to eyelid edema).

❖ Stellwag's sign

Rare blinking.

❖ Kocher's sign

Fixed gaze.

❖ Eyelid flutters when closed

— Patient with Graves' disease, more severe in the left than in the right eye. -

Fig. 15.3 Typical signs include exophthalmos, which here is readily apparent in the left eye, retraction of the upper eyelid with visible sclera superior to the lim-bus (Dalrymple's sign), conjunctival injection, and fixed gaze (Kocher's sign).

The tentative clinical diagnosis of Graves' disease is supported by thickening 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.

— CT image of a patient with Graves' disease.

Fig. 15.4 The image shows obvious thickening of the extraocular muscles in the right orbit, primarily the rectus medialis (1) and rectus lateralis (2), and of the rectus medialis (3) in the left orbit.

Fig. 15.4 The image shows obvious thickening of the extraocular muscles in the right orbit, primarily the rectus medialis (1) and rectus lateralis (2), and of the rectus medialis (3) in the left orbit.

Differential diagnosis: Rarer clinical syndromes such as orbital tumors and orbital pseudotumors must be excluded.

Treatment: The main principles in treating the disease in its acute stage include management of the thyroid dysfunction, systemic cortisone (initially 60 -100 mg of prednisone) and radiation therapy of the orbital cavity. Surgical decompression of the orbital cavity is indicated in recurrent cases that do not respond to treatment to avoid compressive optic neuropathy. Exposure keratitis (keratitis due to inability to close the eye) should be treated with artificial tears or tarsorrhaphy (partial or complete suture closure of the upper and lower eyelid to shorten or close the palpebral fissure). In the postinflammatory stage of the disease, eye muscle surgery may be performed to correct strabismus.

Clinical course and prognosis: Visual acuity will remain good if treatment is initiated promptly. In the postinflammatory phase, exophthalmos often persists despite the fact that the underlying disorder is well controlled.

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