Exophthalmos (Proptosis)

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Background

Exophthalmos is defined in Dorland's Medical Dictionary as an "abnormal protrusion of the eyeball; also labeled as proptosis." Proptosis in the same reference is defined as exophthalmos. Another resource suggests that the terms exophthalmos and proptosis can be used to describe eyes appearing to bulge out of the face due to an increase in the volume of the tissue behind the eyes. Proptosis can describe any organ that is displaced forward, while exophthalmos refers to only the eyes.[1, 2, 3] Proptosis can include any directional forward displacement.

Henderson reserves the use of the word exophthalmos for those cases of proptosis secondary to endocrinological dysfunction.[4] Therefore, this dictum will be followed, and non–endocrine-mediated globe protrusion will be referred to as proptosis and exophthalmos will be reserved for protrusion secondary to endocrinopathies. See the image below.



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Bilateral exophthalmos and upper lid retraction secondary to Graves disease.



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Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes with bilateral upper- and lower-lid retraction. Im....



View Image

Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes and bilateral upper- and lower-lid retraction. Als....

Pathophysiology

The etiological basis of proptosis can include inflammatory, vascular, infectious, cystic, neoplastic (both benign and malignant, metastatic disease), and traumatic factors.[5] Some representative examples (not a complete list of proptosis from different causes) include infectious causations such as orbital cellulitis and subperiosteal abscesses. Traumatic causations could be orbital emphysema, retro-orbital hemorrhage, and carotid-cavernous fistula. Vascular causations not traumatically related would be orbital arteriovenous malformation (AVM) varices and aneurysms. Neoplastic causations include adenocarcinoma of the lacrimal gland, pleomorphic adenoma of the lacrimal gland, meningioma, lymphoma, and metastatic disease.

For instance, lymphangiomas, by their histologic nature, can increase in size during viral illnesses and result in an increase in orbital volume.[5] A ruptured lymphangioma can enlarge after its rupture and sequestering of heme, which pathologically is described as a chocolate cyst. Orbital varices can result in proptosis with increased venous pressure in the orbit, as seen with a Valsalva maneuver or change in postural position.

Unusual cases are also encountered, such as bilateral proptosis due to orbital hemorrhage caused by factor IX deficiency (hemophilia B).[6]

In children, unilateral proptosis is often due to an orbital cellulitis–type picture, and, in bilateral cases, neuroblastoma and leukemia are more likely. Other causes in children include rhabdomyosarcoma, retinoblastoma, capillary hemangioma, dermoid cyst, glioma of the optic nerve, and metastatic disease.

Thyroid orbitopathy, also referred to as thyroid ophthalmopathy, is categorized as an inflammatory process that is autoimmune-mediated.[5, 7]  As it affects the orbit, the author prefers to use thyroid orbitopathy and, more particularly, thyroid-associated orbitopathy, commonly referred to as Graves disease. In adults, it is the most common cause of unilateral and bilateral exophthalmos. Noninflammatory thyroid orbitopathy has also been reported.[8]

The etiology of the thyroid-related orbitopathy is an autoimmune-mediated inflammatory process of the orbital tissues, predominantly affecting the fat and the extraocular muscles. Lymphocytes, plasma, and mast cells are the cellular constituents in this process. The deposition of glycosaminoglycans and the influx of water increase the orbital contents. Over time, fibrosis can occur.[9, 10] Genetic factors have been associated with Graves disease.[11] Obstruction of the superior ophthalmic vein with resultant diminished venous outflow also contributes to the orbital engorgement.

Nunery has segregated patients with thyroid-related orbitopathy into type I and type II.[12] Those with type I do not have restrictive myopathy, whereas those with type II do. Type I was believed to be caused by a profundity of hyaluronic acid manufactured by the orbital fibroblasts, stimulating lipoid hyperplasia and edema. Patients with type II experience restrictive myopathy and have diplopia within 20° of fixation.

Orbital emphysema can be a significant cause of proptosis and requires emergency treatment.

No matter what the etiology may be, globular protrusion is secondary to the increase in volume within the fixed bony orbital confines. Since the orbit is widest toward its anterior aspect, the orbital contents are displaced anteriorly, resulting in proptosis and exophthalmos.

Epidemiology

Frequency

Five percent of the general population is affected by thyroid autoimmunity problems.[7]

United States

Bartley et al reported a frequency of 2.9 cases per 100,000 population per year in men and 16 cases per 100,000 population per year in women. They also observed a bimodal distribution in both sexes, with women showing one peak at age 40-44 years and the other peak at age 60-64 years. In men, the bimodal occurrence was at age 45-49 years and age 65-69 years. Both peaks incidences in men were 5 years later than in women.[13]

International

In a nationwide registry-based cohort study conducted in Denmark between 2000 and 2018, researchers investigated the incidence of thyroid eye disease (TED), strabismus, and surgical interventions related to TED. The study included a cohort of approximately 4.3 million individuals aged 18 to 100 years with no prior TED diagnosis each year. The total observation time amounted to 8.22 million person-years (women accounting for 4.18 million person-years and men for 4.04 million person-years).

Over 19 years, there were 4106 new cases of thyroid eye disease (TED) documented, with a prevalence of 81.4% among women and 18.6% among men. The average annual incidence rate of TED was 5.0 per 100,000 person-years, significantly higher in women (8.0 per 100,000 person-years) than in men (1.9 per 100,000 person-years), resulting in a notable 4:1 ratio. The average age of onset for TED was 51.3 years. At the time of diagnosis, 14.9% of patients were euthyroid, 11.6% were hypothyroid, and 73.5% were hyperthyroid. In patients who were euthyroid, the 4-year cumulative incidence for antithyroid medication was 41%, whereas for L-thyroxine, it was 13%. The prevalence of strabismus in TED patients within 4 years was 10%. Surgical interventions, including strabismus surgery and orbital decompression, had a 4-year cumulative rate of 8% and 5%, respectively. Men had a higher likelihood of undergoing strabismus surgery compared to women 4 years post-TED diagnosis.[14]

Predictive

In a report from the European Group on Graves’ Orbitopathy (EUGOGO), 15% of patients who did not have orbitopathy at the time of diagnosis of Graves hyperthyroidism went on to develop orbitopathy.[15]

Mortality/Morbidity

Proptosis due to any cause can compromise visual function and the integrity of the eye.

A proptotic eye not adequately protected by the lids, as with lagophthalmos, can develop exposure punctuate keratopathy. Such disruption of the finely orchestrated homeostatic mechanism to protect the eye will result in corneal compromise, epithelial death, ulceration, and possible corneal perforation in severe cases. At a minimum, the disruption of the tear film layer and incomplete moisturizing of the eye will adversely affect vision and ocular comfort.

Proptosis secondary to a space-occupying process can result in a compressive optic neuropathy. Impeded optic nerve blood flow results in irreversible neuronal death and diminished optic nerve function. Such manifestations as depression of visual and color acuities, pupillary dysfunction, and constriction of visual field can occur.

Proptotic compressive effects are remedied initially by forward protrusion of the eye, thereby reducing the compressive effect within the orbit. However, the eye can extend only so far, and severe stretching can adversely affect the eye and compromise the optic nerve.

A difference of more than 2 mm between the 2 eyes of any given patient is considered abnormal.

Race

Epstein et al state that proptosis is a globe that protrudes 18 mm or less and exophthalmos is protrusion of greater than 18 mm. The upper limit of normal was 21 mm.[16]

In adult white males, the average distance of globe protrusion is 16.5 mm, with the upper limit of normal at 21.7 mm.[17]

In adult African American males, it averages 18.5 mm, with the upper limit of normal reported as 24.7 mm.[17] A separate study reported the average as 18.2 mm, with an upper normal limit of 24.14 mm in males and 22.74 mm in females.[18]

In Mexican adults, males averaged 15.18 mm and females averaged 14.83 mm.[19]

In Tehran, Iran, for the age group of 20-70 years, the average was 14.7 mm.[20]

In Taiwanese adults, comparing normal subjects to those with Graves disease, the normal group had an average reading of 13.91 mm versus 18.32 mm for the Graves disease group.[21]

Even within a group of people, there can be variability. Four ethnic groups in Southern Thailand had exophthalmometry measurement averages ranging from 15.4 mm to 16.6 mm.[22]

In 2477 Turkish patients, the median Hertel measurement was 13 mm, with an upper limit of 17 mm.[23]

In a Dutch study, the upper limit by Hertel measurement was 20 mm in males and 16 mm in females.[24]

Sex

Females also show racial variation. The average in white women was 15.4 mm and the average was 17.8 mm in African American women. The upper limits of normal in each group were 20.1 mm and 23 mm, respectively.

In general, adult females across all races have lower exophthalmometry readings than adult males.

Thyroid orbitopathy has a female preponderance, with a female-to-male ratio of 5:1. However, these differences diminish for the more serve cases of ophthalmopathy. The incidence of severe ophthalmopathy is 3-5%.[25] The female to male ratio in this subgroup is 1.4:1.[26, 9, 27]

Age

Proptosis occurs in both adults and children at any age. Thyroid orbitopathy and the resultant exophthalmos show a predilection for females aged 30-50 years.

Ahmadi et al showed that with increasing age occurs a "linear reduction in ocular protrusion." With advancing age, there was no asymmetries between the eyes noted.[28]

A US pediatric population showed exophthalmometry measurements that increased with increasing age, as one would expect. The results were stratified into age groups with the following corresponding averages:

Of the 673 subjects in this study, only 2 had a 2-mm difference between the eyes.[29]

In Tehran, Iran, for the age group 6-12 years, the average was 14.2 mm and for the age group 13-19 years, the average was 15.2 mm.[20]

In Chinese children and adolescents from Xiamen, in the age range from 5-17 years, the average exophthalmometry reading was 14.48 mm.[30]

Note that CT scanning and exophthalmometry yield measurements that are not identical, especially when proptosis is present.[31] In addition, parallax errors exist with most commonly used measuring devices.[32]

History

A meticulous history of the patient's ocular and systemic systems is essential in establishing a diagnosis. The ophthalmic history should address the duration and rate of onset of proptosis, along with symptoms such as pain, changes in visual acuity or refraction, diplopia, and decreased fields of vision. Transient visual loss may signify optic nerve compromise, requiring rapid intervention.

Complaints of foreign body sensation or dry, gritty eyes may indicate corneal decompensation. Consideration should be given to orbital involvement secondary to systemic pathology in a thorough medical history and review of systems.

Past trauma and family history can also play a role in diagnosis. The rate of onset can provide valuable clues - sudden unilateral onset suggesting intraorbital hemorrhage or inflammation, a 2- to 3-week onset suggesting chronic inflammation, and a slower onset pointing to an orbital tumor. By carefully examining all these factors, a comprehensive understanding of the patient's condition can be achieved.[5]

Physical

Evaluation of the patient with exophthalmos begins with a thorough ophthalmic and medical history. When concomitant sinus disease or an intranasal source is suspected, a speculum or endoscopic intranasal examination is warranted. Special emphasis on the duration and rate of progression of the patient's signs and symptoms is essential. Pain, diplopia, pulsation, change in effect or size with position or Valsalva maneuver, and disturbance of visual acuity are symptoms that should be explored. In general, a difference of more than 2 mm between a person's 2 eyes is abnormal.

A comprehensive ophthalmic examination is vital for diagnosing eye conditions accurately. Periorbital changes, including hypertelorism, exorbitism, proptosis, eyelid lesions, edema, chemosis, and engorged conjunctival vessels, should be carefully observed. Additional signs like blepharoptosis, lagophthalmos, and interpalpebral fissure distance also play a crucial role in the examination process.

Palpating the anterior orbit can provide valuable information on tenderness, texture, and mass mobility, indicating possible inflammatory processes or neural invasion. Regional lymph nodes should also be assessed during the examination. Protrusion of the eye is a significant clinical sign of orbital disease, with Hertel exophthalmometry being a reliable tool for measuring proptosis.

Auscultating the orbit may help detect high flow states while examining with the bell. It is essential to note any decrease in visual acuity, changes in refraction, pupillary abnormalities, extraocular motility dysfunction, and diplopia. Forced duction testing can determine whether dysfunction is restrictive or neurogenic in nature.

Intraocular pressure, slit lamp examination, and dilated funduscopic examination are essential for identifying various eye conditions. Funduscopic examination can reveal optic disc abnormalities, retinal detachment, vascular issues, or indentation of the posterior pole. Signs of hyperthyroidism, such as eyelid retraction and lag, can also be observed in ophthalmic examinations. Prolonged exposure to air can lead to corneal drying and potential infection, underscoring the importance of a thorough examination process in diagnosing eye health issues accurately.[5]

The following findings are especially worrisome[5] :

Causes

Proptosis can be the result of a myriad of disease processes resulting from primary orbital pathology or systemic disease processes. The list below is not comprehensive but can help in forming a differential diagnosis. The list only consists of adult causes since a fair amount of overlap exists in the differential diagnosis of exophthalmos in adults and children.

Approach Considerations

Graves disease is the primary cause of bilateral proptosis in adults. Acute unilateral proptosis typically is associated with infection or vascular disorders such as hemorrhage or cavernous sinus thrombosis, whereas chronic unilateral proptosis often is indicative of a tumor. Suspected cases of Graves disease should prompt the performance of CT or MRI scans as well as thyroid function testing. Additionally, it is important to provide lubrication to safeguard the exposed cornea.[5]

Laboratory Studies

Patients with thyroidopathy should undergo the appropriate thyroid function studies, even though some patients are euthyroid at the time of presentation with exophthalmos. Approximately 80% of those with Graves disease manifest orbital signs within 18 months, supporting the need for ophthalmic evaluation.

Any patient suspected of having a neoplasm as the cause of the proptosis should undergo imaging studies (see Imaging Studies). The imaging results should direct further laboratory studies. For example, in a patient with proptosis due to lymphoma, hematologic studies, further body imaging, and a bone marrow biopsy may be indicated.

In patients with proptosis due to orbital cellulitis, complete blood counts, blood and nasal cultures, and sinus imaging studies may be warranted.

Imaging Studies

Proptosis, or bulging of the eye, can be assessed using exophthalmometry, which measures the distance between the lateral angle of the bony orbit and the cornea. Normal values are generally below 20 mm, but may vary depending on race, ethnicity, and gender. Confirmatory imaging tests like CT or MRI of the orbits are often crucial for diagnosing and identifying the underlying structural causes of unilateral proptosis. In cases where Graves disease is suspected, thyroid function testing is recommended.[5]

CT scan, first used in the 1970s, is the product of tissue density calculations. X-rays with different vectors are emitted, penetrating through target tissues with resulting radioabsorbencies. These differences in radioabsorbencies are assigned value-specific gray shades to create the 2-dimensional image. CT scan can produce detailed axial and coronal views of soft tissue and bony structures. Image windows from 1.0-3.0 mm in thickness allow for detailed evaluation of orbital masses. Contrast-enhanced images may be obtained and can help in identifying inflammatory processes, vascular tumors, and engorged vessels. Calcified lesions are discernible without the addition of contrast.

Magnetic resonance imaging (MRI) excites protons by applying a radio frequency with a strong magnetic field. Hydrogen nuclei emit signal intensities that are assigned specific gray tones to create an anatomical reproduction. Three-dimensional views can be gained directly, in any anatomical plane, offering excellent spatial resolution of orbital masses and soft-tissue enhancement. MRI may provide excellent soft-tissue resolution, but CT scan is superior for gleaning details about orbital bony structures.

Ocular ultrasonography can be used to visualize anterior and middle orbital lesions. Sound waves of 5-15 MHz breech orbital tissues that reflect echogenic energy captured by an oscilloscope. A-scan ultrasonography allows for a 1-dimensional description of echoes, while B-scan ultrasonography provides a 2-dimensional image. C-scan ultrasonography affords coronal views, and D-scan ultrasonography creates 3-dimensional orbital views. With the advent of CT scan, C- and D-scan ultrasonography remains unpopular. Doppler ultrasonography may be used to evaluate orbital vasculature and blood flow.

Approach Considerations

In severe cases of proptosis, lubrication to protect the cornea is essential. Surgical intervention may be necessary when lubrication is insufficient to provide adequate eye surface coverage or to reduce proptosis. Systemic corticosteroids, such as prednisone, can help control edema and orbital congestion in conditions like thyroid eye disease or inflammatory orbital pseudotumor. Treatment approaches vary depending on the underlying cause, with Graves exophthalmos potentially improving over time independently of thyroid treatment. Tumors typically require surgical removal, while arteriovenous fistulas involving the cavernous sinus may benefit from selective embolization or trapping procedures in rare cases.[5]

Medical Care

Medical care for patients with exophthalmos is directed at reversing the problem and minimizing ocular complications.

The FDA approved teprotumumab (Tepezza) in January 2020 for the treatment of thyroid eye disease in adults. Thyroid eye disease is most often associated with hyperthyroidism or Graves disease, although it arises from a separate process involving autoantibodies that activate an insulinlike growth factor 1 receptor–mediated signaling complex on cells within the eye orbit.

Approval of teprotumumab was supported by the OPTIC phase 2 and 3 clinical trials (n = 171). Results showed that significantly more patients treated with teprotumumab (82.9%) had a meaningful improvement in proptosis (≥2 mm) compared with placebo (9.5%) (P ˂ 0.001) without deterioration in the fellow eye at week 24. Additional secondary endpoints were also met, including a change from baseline of at least 1 grade in diplopia (in 67.9% of patients receiving teprotumumab compared with 28.6% receiving placebo (P = 0.001) at week 24.[36, 37]

Consultations

Once the etiology of exophthalmos or proptosis is established, the appropriate specialists should partake in the patient's care.

Long-Term Monitoring

Patients should be monitored in intervals tailored to the degree of exophthalmos and complications arising from this ocular malady. Measurement of exophthalmos, visual and color acuities, pupillary function, extraocular motilities, and visual fields should be obtained. In addition, any corneal breakdown should be assessed and remedied.

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

The FDA approved teprotumumab (Tepezza) in January 2020 for the treatment of thyroid eye disease in adults. Approval of teprotumumab was supported by the OPTIC phase 2 and 3 clinical trials (n = 171). Results showed that significantly more patients treated with teprotumumab (82.9%) had a meaningful improvement in proptosis (≥2 mm) compared with placebo (9.5%) (P ˂ 0.001).[36, 37]

Teprotumumab (Tepezza, Teprotumumab-trbw)

Clinical Context:  Monoclonal antibody that binds insulin-like growth factor-1 receptor (IGF-1R). It is indicated for treatment of thyroid eye disease.

Class Summary

Autoantibodies that activate an insulinlike growth factor 1 receptor–mediated signaling complex on cells within the eye orbit contribute to thyroid eye disease. Teprotumumab attenuates the actions of both IGF-1 and TSH in fibrocytes by blocking the induction of proinflammatory cytokines by TSH.

Artificial tears (Celluvisc, Murine, Refresh, Tears Naturale)

Clinical Context:  Contains equivalent of 0.9% NaCl and maintains ocular tonicity. Acts to stabilize and thicken precorneal tear film and prolongs tear film breakup time, which occurs with dry eye states.

Polyethylene glycol 400/propylene glycol ophthalmic (Systane Balance, Systane Ultra, Tears Naturale Free, Hypo Tears, Murine Tears)

Clinical Context:  These substances serve as lubricants.

Carboxymethylcellulose ophthalmic (Refresh Optive Gel Drops, TheraTears Nighttime Dry Eye Therapy)

Clinical Context:  Carboxymethylcellulose is used to protect and lubricate mucous membranes surfaces and relieve dryness and irritation.

Hypromellose/carboxymethylcellulose ophthalmic (Genteal Lubricant Eye Drops, Moderate-to-Severe)

Clinical Context:  Increases lubrication of the eye, which in turn prevents complications and reduces morbidity.

Class Summary

Lubricants act as humectants in the eye. The ideal artificial lubricant should be preservative-free  and have a polymeric system to increase its retention time. Lubricating drops are used to reduce morbidity and to prevent complications. Lubricating ointments prevent complications from dry eyes.

Author

Michael Mercandetti, MD, MBA, FACS, Private Practice

Disclosure: Nothing to disclose.

Coauthor(s)

Adam J Cohen, MD, Physician/CEO, Eyelid and Facial Plastic Surgery and Aesthetic Lounge MedSpa

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Triad Inc.<br/>Serve(d) as a speaker or a member of a speakers bureau for: Mimedx; InMode.

Specialty Editors

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

J James Rowsey, MD, Former Director of Corneal Services, St Luke's Cataract and Laser Institute

Disclosure: Nothing to disclose.

Chief Editor

Hampton Roy, Sr, MD, † Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Disclosure: Nothing to disclose.

Additional Contributors

Brian A Phillpotts, MD, Ophthalmologist, St Luke's Cataract and Laser Institute

Disclosure: Nothing to disclose.

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Bilateral exophthalmos and upper lid retraction secondary to Graves disease.

Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes with bilateral upper- and lower-lid retraction. Image courtesy of Adam J. Cohen, MD.

Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes and bilateral upper- and lower-lid retraction. Also note conjunctival injection, especially of the right inferomedial conjunctiva. Image courtesy of Adam J. Cohen, MD.

Bilateral exophthalmos and upper lid retraction secondary to Graves disease.

Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes with bilateral upper- and lower-lid retraction. Image courtesy of Adam J. Cohen, MD.

Exophthalmos due to thyroid dysfunction. The patient has significant forward protrusion of the eyes and bilateral upper- and lower-lid retraction. Also note conjunctival injection, especially of the right inferomedial conjunctiva. Image courtesy of Adam J. Cohen, MD.