Title: Proptosis/Graves’ Disease
Author: Blake Fortes, 4th Year Medical Student, Florida International University Herbert Wertheim College of Medicine
Image 1: A patient with severe thyroid-associated ophthalmopathy which resulted in conjunctival chemosis (conjunctival swelling) and periorbital edema.
Image 2: A patient with thyroid-associated ophthalmopathy. Note the inferior scleral show, and conjunctival injection.
Definition: Proptosis, or exophthalmos, refers to a protrusion of the eyeball caused by an increase in orbital pressure or contents.
Introduction: In adults, the most common cause of both unilateral and bilateral proptosis is thyroid ophthalmopathy related to Graves’ disease, whereas the most common cause of unilateral proptosis in children is orbital cellulitis. Thyroid-associated ophthalmopathy (TAO) is the most common extrathyroidal manifestation of Graves’ disease, which is an autoimmune condition characterized by hyperthyroidism and diffuse goiter as a result of thyroid stimulating immunoglobulin (TSI).
Clinical Manifestations: The four critical sequelae of TAO are eyelid disorders, eye surface disorders, ocular motility disorders, and optic neuropathy. The symptoms include red eye, ocular pain or discomfort, foreign body sensation, tearing, binocular diplopia, dyschromatopsia, and decreased visual acuity. Signs on physical exam include eyelid retraction, lid lag, lagophthalmos, and staring appearance related to increased sympathetic innervation; reduced blinking, conjunctival injection and superficial keratopathy related to exposure; limitation of extraocular motility as a result of periorbital edema and stimulation of retroocular fibroblasts; and decreased visual acuity, decreased color vision, relative afferent pupillary defect, and visual field defect as a result of optic neuropathy in the most advanced cases. See table below for summary:
|Critical Sequelae of TAO||Symptoms||Signs|
|Eye Surface Disorders||Red eye, ocular pain, foreign body sensation, tearing||Conjunctival injection, exposure keratopathy (secondary to poor eyelid coverage)|
|Eyelid Disorders||Dry eye, red eye, eye discomfort and foreign body sensation||Lid retraction, lid lag, lagophthalmos (inability to close eyes), staring appearance, reduced blinking|
|Motility Disorders||Binocular diplopia||Decreased or restricted motility, new strabismus|
|Optic Neuropathy||Dyschromatopsia (abnormal color vision), dimming or decreased vision, pain||Proptosis, Decreased visual acuity, relative afferent pupillary defect (RAPD), decreased color vision, visual field defect|
Differential Diagnosis: In acutely presenting exophthalmos other diagnoses to consider include orbital cellulitis, orbital hemorrhage, cavernous sinus thrombosis and cavernous sinus fistula. More subacute/chronic causes are metastatic tumors, orbital pseudotumor, and primary orbital tumors, such as hemangioma, rhabdomyosarcoma, dermoid cyst, lipoma, meningioma, and optic nerve glioma, among others.
Work-up: Conduct a complete ophthalmic and medical history with attention to prior thyroid disease, autoimmune disease, cancers and hyperthyroid symptoms such as palpitations, heat intolerance, weight loss, diaphoresis, tremor, and anxiety. Depending on your resources, complete an eye exam including visual acuity, pupils, extraocular motility, lids, cornea, tonometry, and ophthalmoscopy if able. Signs of an optic neuropathy (decreased visual acuity, RAPD, decreased color vision, severely limited motility) are a medical emergency and the patient should be transferred urgently to a facility that has the capacity to perform urgent orbital wall decompressions, typically done by an oculoplastic specialist.
In non-urgent cases, look carefully for proptosis and lid lag. Proptosis may be best appreciated by looking upward while the patient’s head is tilted back, gauging how far the eyes bulge forward as compared to the surrounding bony facial structures such as the cheek and forehead. It can be measured objectively with an exophthalmometer, but these are not typically widely available outside ophthalmology offices. Lab evaluation consists of thyroid function tests (thyroid stimulating hormone, thyroxine [total and free T4], triiodothyronine [T3], and TSI. Orbital CT scan with contrast or MRI is indicated when the cause of ocular symptoms is uncertain, as it may exclude orbital tumors and arteriovenous malformations. The patient should promptly be evaluated by an ophthalmologist where additional testing can be performed to arrive to a definitive diagnosis.
Treatment: As mentioned above, any patient with a possible optic neuropathy should urgently be sent to an emergency room who has an oculoplastics specialist available on call. Otherwise, the practitioner should consult endocrinology for management of any underlying thyroid disease. Ironically, patients can develop TAO independent of their thyroid status. For instance, radioactive iodine therapy may lead to new ophthalmopathy or exacerbate existing ophthalmopathy. Surgical interventions are deferred for a 9-12 month period of stability, unless optic neuropathy or extreme proptosis resulting in severe exposure keratopathy is present. Surgery is a stepwise approach beginning with orbital bony decompression, followed by strabismus surgery, and eyelid reconstruction as indicated. The four critical sequelae of TAO must be managed prior to surgical intervention. Exposure is managed with artificial tears, lid taping, punctal occlusion, or permanent lateral tarsorrhaphy depending on symptom severity. Surgical eyelid recession is performed after a sufficient stable interval. Diplopia may be managed with) prisms, or an eye patch until a 6-month stable interval is reached at which point strabismus surgery is indicated. Immediate treatment with oral or intravenous steroids is indicated to treat optic neuropathy, followed by orbital decompression. Recently, intravenously administered pulse glucocorticoids have been associated with a favorable adverse effect profile.
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