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

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

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 a ...

. Exophthalmos can be either bilateral (as is often seen in Graves' disease) 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, 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 ...

or ophthalmic artery, 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 due to Graves' disease, usually causes bilateral proptosis. * Orbital cellulitis – often with unilateral proptosis, severe redness, and moderate to severe pain, sinusitis and an elevated white blood cell count. * Dacryoadenitis * Erdheim–Chester disease * Mucormycosis *

Orbital pseudotumor Idiopathic orbital inflammatory (IOI) disease refers to a marginated mass-like enhancing soft tissue involving any area of the orbit. It is the most common painful orbital mass in the adult population, and is associated with proptosis, cranial ner ...

– presents with acute, usually unilateral proptosis with severe pain. * High-altitude cerebral edema *

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, (of sphenoid wing) * Nasopharyngeal angiofibroma * Hand–Schüller–Christian disease * Hemangioma, cavernous Cystic: * Dermoid cyst Vascular: * Carotid-cavernous fistula * 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 (due to fat in the orbital cave) * Some forms of craniosynostosis: **

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 An exophthalmometer is an instrument used for measuring the degree of forward displacement of the eye in exophthalmos. The device allows measurement of the forward distance of the lateral orbital rim to the front of the cornea. Exophthalmometers ...

. 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 Graves' disease.

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 secondary to exposure of the

. Exophthalmos is commonly seen in the pug, Boston terrier, Pekingese, and shih tzu. It is a common result of head trauma 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. 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 for about five days to keep the eye in place. Replaced eyes have a higher rate of keratoconjunctivitis sicca and keratitis and often require lifelong treatment. If the damage is severe, the eye is removed in a relatively simple surgery 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 stabl ...

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

and sclera, 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, the ...

, 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 In ...

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