Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

. Exophthalmos can be either bilateral (as is often seen in

Graves' disease Graves' disease (german: Morbus Basedow), also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyro ...

) or unilateral (as is often seen in an orbital tumor). Complete or partial dislocation from the orbit is also possible from trauma or swelling of surrounding tissue resulting from trauma. In the case of Graves' disease, the displacement of the eye results from abnormal connective tissue deposition in the orbit and

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...

, which can be visualized by CT or MRI. If left untreated, exophthalmos can cause the eyelids to fail to close during sleep, leading to

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...

l dryness and damage. Another possible complication is a form of redness or irritation called

superior limbic keratoconjunctivitis Superior limbic keratoconjunctivitis (SLK, Théodore's syndrome) is a disease of the eye characterized by episodes of recurrent inflammation of the superior cornea and limbus, as well as of the superior tarsal and bulbar conjunctiva. It was first ...

, in which the area above the cornea becomes inflamed as a result of increased friction when blinking. The process that is causing the displacement of the eye may also compress the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

ophthalmic artery The ophthalmic artery (OA) is an artery of the head. It is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the ophthalmic artery supply all the structures in the orbit around the eye, as well as some s ...

, and lead to

blindness Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

Causes

Inflammatory/Infection: *

Graves' ophthalmopathy Graves’ ophthalmopathy, also known as thyroid eye disease (TED), is an autoimmune inflammatory disorder of the orbit and periorbital tissues, characterized by upper eyelid retraction, lid lag, swelling, redness (erythema), conjunctivitis, and ...

due to

, usually causes bilateral proptosis. * Orbital cellulitis – often with unilateral proptosis, severe redness, and moderate to severe pain,

sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include thick nasal mucus, a plugged nose, and facial pain. Other signs and symptoms may include fever, head ...

and an elevated white blood cell count. *

Dacryoadenitis Dacryoadenitis is inflammation of the lacrimal glands. Symptoms * Swelling of the outer portion of the upper lid, with possible redness and tenderness * Pain in the area of swelling * Excess tearing or discharge * Swelling of lymph nodes in fro ...

Erdheim–Chester disease Erdheim–Chester disease (ECD) is an extremely rare disease characterized by the abnormal multiplication of a specific type of white blood cells called histiocytes, or tissue macrophages (technically, this disease is termed a non- Langerhans ...

Mucormycosis Mucormycosis, also known as black fungus, is a serious fungal infection that comes under fulminant fungal sinusitis, usually in people who are immunocompromised. It is curable only when diagnosed early. Symptoms depend on where in the body the ...

* Orbital pseudotumor – presents with acute, usually unilateral proptosis with severe pain. *

High-altitude cerebral edema High-altitude cerebral edema (HACE) is a medical condition in which the brain swells with fluid because of the physiological effects of traveling to a high altitude. It generally appears in patients who have acute mountain sickness and involves dis ...

Granulomatosis with polyangiitis Granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis (WG), is a rare long-term systemic disorder that involves the formation of granulomas and inflammation of blood vessels (vasculitis). It is a form of vasculitis ...

Neoplastic: *

Leukemia Leukemia ( also spelled leukaemia and pronounced ) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or ...

s *

Meningioma Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing ...

, (of sphenoid wing) *

Nasopharyngeal angiofibroma Nasopharyngeal angiofibroma is an angiofibroma also known as juvenile nasal angiofibroma, fibromatous hamartoma, and angiofibromatous hamartoma of the nasal cavity. It is a histologically benign but locally aggressive vascular tumor of the nasopha ...

* Hand–Schüller–Christian disease *

Hemangioma A hemangioma or haemangioma is a usually benign vascular tumor derived from blood vessel cell types. The most common form, seen in infants, is an infantile hemangioma, known colloquially as a "strawberry mark", most commonly presenting on the ski ...

, cavernous Cystic: *

Dermoid cyst A dermoid cyst is a teratoma of a cystic nature that contains an array of developmentally mature, solid tissues. It frequently consists of skin, hair follicles, and sweat glands, while other commonly found components include clumps of long hair ...

Vascular: *

Carotid-cavernous fistula A carotid-cavernous fistula results from an abnormal communication between the arterial and venous systems within the cavernous sinus in the skull. It is a type of arteriovenous fistula. As arterial blood under high pressure enters the cavernous s ...

* Aortic insufficiency: manifests as a pulsatile pseudoproptosis, described by British cardiothoracic surgeon Hutan Ashrafian in 2006 Others: * Orbital fracture: apex, floor, medial wall, zygomatic * Retrobulbar hemorrhage: trauma to the orbit can lead to bleeding behind the eye. The hemorrhage has nowhere to escape and the increased pressure pushes the eye out of the socket, leading to proptosis and can also cause blindness if not treated promptly. *

Cushing's syndrome Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a ...

(due to fat in the orbital cave) * Some forms of

craniosynostosis Craniosynostosis is a condition in which one or more of the fibrous sutures in a young infant's skull prematurely fuses by turning into bone (ossification), thereby changing the growth pattern of the skull. Because the skull cannot expand perpe ...

: **

Crouzon syndrome Crouzon syndrome is an autosomal dominant genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial (or pharyngeal) arch, which is the precursor of the maxilla and mandible. Since the branchial ...

** Pfeiffer syndrome ** Pansynostosis

Anatomy

Proptosis is the anterior displacement of the eye from the orbit. Since the orbit is closed off posteriorly, medially and laterally, any enlargement of structures located within will cause the anterior displacement of the eye. Swelling or enlargement of the lacrimal gland causes inferior medial and anterior dislocation of the eye. This is because the lacrimal glands are located superiorly and laterally in the orbit.

Diagnosis

Measurement

Measurement of the degree of exophthalmos is performed using an exophthalmometer. Most sources define exophthalmos/proptosis as a protrusion of the globe greater than 18 mm. The term exophthalmos is often used when describing proptosis associated with

Animals

Exophthalmos is commonly found in dogs. It is seen in brachycephalic (short-nosed) dog breeds because of the shallow

. It can lead to

keratitis Keratitis is a condition in which the eye's cornea, the clear dome on the front surface of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves any of the following symptoms: pain, impaired e ...

secondary to exposure of the

. Exophthalmos is commonly seen in the pug,

Boston terrier The Boston Terrier is a breed of dog originating in the United States of America. This "American Gentleman" was accepted in 1893 by the American Kennel Club as a non-sporting breed. Color and markings are important when distinguishing this breed f ...

Pekingese The Pekingese (also spelled Pekinese) is a breed of toy dog, originating in China. The breed was favored by royalty of the Chinese Imperial court as a companion dog, and its name refers to the city of Peking (Beijing) where the Forbidden City i ...

, and

shih tzu The Shih Tzu (, ; literally " Hsi Shih dog") is a toy dog breed originating from Tibet and was bred from the Pekingese and the Lhasa Apso. Shih Tzus are known for their short snouts and large round eyes, as well as their long coat, floppy ea ...

. It is a common result of

head trauma A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

and pressure exerted on the front of the neck too hard in dogs. In cats, eye proptosis is uncommon and is often accompanied by facial fractures. About 40% of proptosed eyes retain vision after being replaced in the

, but in cats very few retain vision. Replacement of the eye requires general

anesthesia Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), ...

. The eyelids are pulled outward, and the eye is gently pushed back into place. The eyelids are sewn together in a procedure known as

tarsorrhaphy Tarsorrhaphy is a surgical procedure in which the eyelids are partially sewn together to narrow the eyelid opening. It may be done to protect the cornea in cases of corneal exposure, as a treatment for Graves' ophthalmopathy, Möbius syndrome or ...

for about five days to keep the eye in place. Replaced eyes have a higher rate of keratoconjunctivitis sicca and

and often require lifelong treatment. If the damage is severe, the eye is removed in a relatively simple

surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pa ...

known as enucleation of the eye. The

prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing") is a medical term for predicting the likely or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) or remain sta ...

for a replaced eye is determined by the extent of damage to the

and

sclera The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and so ...

, the presence or absence of a

pupillary light reflex The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, ther ...

, and the presence of ruptured

rectus muscle Rectus muscle (Latin: , "straight muscle") may refer to: In the trunk: * Rectus abdominis muscle In the eye: * Inferior rectus muscle * Lateral rectus muscle * Medial rectus muscle * Superior rectus muscle In the leg: * Rectus femoris muscle I ...

s. The rectus muscles normally help hold the eye in place and direct eye movement. Rupture of more than two rectus muscles usually requires the eye to be removed, because significant blood vessel and nerve damage also usually occurs. Compared to brachycephalic breeds, dochilocephalic (long-nosed) breeds usually have more trauma to the eye and its surrounding structures, so the prognosis is worse.

References

External links

{{Eye pathology Dog diseases Disorders of eyelid, lacrimal system and orbit