Coats disease
Encyclopedia
Coats’ disease, is a very rare congenital, nonhereditary eye disorder, causing full or partial blindness
, characterized by abnormal development of blood vessels behind the retina
.
It can have a similar presentation to that of retinoblastoma
.
Coats’ disease results in a gradual loss of vision. Blood leaks from the abnormal vessels into the back of the eye, leaving behind cholesterol deposits and damaging the retina. Coats’ normally progresses slowly. At advanced stages, retinal detachment
is likely to occur. Glaucoma
, atrophy
, and cataracts can also develop secondary to Coats’ disease. In some cases, removal of the eye may be necessary (enucleation).
(abnormal white reflection of the retina). Symptoms typically begin as blurred vision, usually pronounced when one eye is closed (due to the unilateral nature of the disease). Often the unaffected eye will compensate for the loss of vision in the other eye; however, this results in some loss of depth perception
and parallax
. Deterioration of sight may begin in either the central or peripheral vision. Deterioration is likely to begin in the upper part of the vision field as this corresponds with the bottom of the eye where blood usually pools. Flashes of light, known as photopsia
, and floaters are common symptoms. Persistent color patterns may also be perceived in the affected eye. Initially, these may be mistaken for psychological hallucinations, but are actually the result of both retinal detachment
and foreign fluids mechanically interacting with the photoreceptors located on the retina.
One early warning sign of Coats’ disease is yellow-eye in flash photography. Just as the red-eye effect
is caused by a reflection off blood vessels in the back of a normal eye, an eye affected by Coats’ will glow yellow in photographs as light reflects off cholesterol deposits. Children with yellow-eye in photographs are typically advised to immediately seek evaluation from an ophthalmologist, preferably a vitreo-retinal specialist.
Coats’ disease itself is painless. Pain may occur if fluid is unable to drain from the eye properly, causing the internal pressure to swell, resulting in painful glaucoma.
in the endothelial cell
, resulting in leakage of blood products containing cholesterol
crystals and lipid-laden macrophage
s into the retina and subretinal space. Over time, the accumulation of this proteinaceous exudate thickens the retina, leading to massive, exudative retinal detachment.
(US), Computerized Tomography (CT) and Magnetic Resonance Imaging
(MRI) can aid diagnosis
. On ultrasound, Coats' disease appears as a hyperechoic mass in the posterior vitreous without posterior acoustic shadowing; vitreous and subretinal hemorrhage may often be observed.
On CT, the globe appears hyperdense compared to normal vitreous due to the proteinaceous exudate, which may obliterate the vitreous space in advanced disease. The anterior margin of the subretinal exudate enhances with contrast. Since the retina is fixed posteriorly at the optic disc, this enhancement has a V-shaped configuration.
On MRI, the subretinal exudate shows high signal intensity on both T1- and T2-weighted images. The exudate may appear heterogeneous if hemorrhage or fibrosis is present. The subretinal space does not enhance with gadolinium contrast. Mild to moderate linear enhancement may be seen between the exudate and the remaining vitreous. The exudate shows a large peak at 1-1.6 ppm on proton MR spectroscopy
.
Microscopically, the wall of retinal vessels may be thickened in some cases, while in other cases the wall may be thinned with irregular dilatation of the lumen. The subretinal exudate consists of cholesterol crystals, macrophages laden with cholesterol and pigment, erythrocytes, and hemosiderin
. A granulomatous reaction, induced by the exudate, may be seen with the retina. Portions of the retina may develop gliosis
as a response to injury.
or cryotherapy
(freezing) can be used to destroy the abnormal blood vessels, thus halting progression of the disease. However, if the leaking blood vessels are clustered around the optic nerve
, this treatment is not recommended as accidental damage to the nerve itself can result in permanent blindness. Although Coats’ disease tends to progress to visual loss, it may stop progressing on its own, either temporarily or permanently. Cases have been documented in which the condition even reverses itself. However, once total retinal detachment occurs, sight loss is permanent in most cases. Removal of the eye (enucleation) is an option if pain or further complications arise.
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
, characterized by abnormal development of blood vessels behind the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
.
It can have a similar presentation to that of retinoblastoma
Retinoblastoma
Retinoblastoma is a rapidly developing cancer that develops in the cells of retina, the light-detecting tissue of the eye. In the developed world, Rb has one of the best cure rates of all childhood cancers , with more than nine out of every ten sufferers surviving into...
.
Presentation
Coats’ usually affects only one eye (unilateral) and occurs predominantly in young males, with the onset of symptoms generally appearing in the first decade of life. Peak age of onset is between 6-8 years of age, but onset can range from 5 months to 71 years.Coats’ disease results in a gradual loss of vision. Blood leaks from the abnormal vessels into the back of the eye, leaving behind cholesterol deposits and damaging the retina. Coats’ normally progresses slowly. At advanced stages, retinal detachment
Retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
is likely to occur. Glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
, atrophy
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...
, and cataracts can also develop secondary to Coats’ disease. In some cases, removal of the eye may be necessary (enucleation).
Signs and Symptoms
The most common sign at presentation is leukocoriaLeukocoria
Leukocoria is an abnormal white reflection from the retina of the eye. Leukocoria resembles eyeshine, but leukocoria can occur in humans and other animals that lack eyeshine because their retina lacks a tapetum lucidum....
(abnormal white reflection of the retina). Symptoms typically begin as blurred vision, usually pronounced when one eye is closed (due to the unilateral nature of the disease). Often the unaffected eye will compensate for the loss of vision in the other eye; however, this results in some loss of depth perception
Depth perception
Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
and parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...
. Deterioration of sight may begin in either the central or peripheral vision. Deterioration is likely to begin in the upper part of the vision field as this corresponds with the bottom of the eye where blood usually pools. Flashes of light, known as photopsia
Photopsia
Photopsia is the presence of perceived flashes of light. It is most commonly associated with posterior vitreous detachment, migraine with aura, migraine aura without headache, retinal break or detachment, occipital lobe infarction and sensory deprivation...
, and floaters are common symptoms. Persistent color patterns may also be perceived in the affected eye. Initially, these may be mistaken for psychological hallucinations, but are actually the result of both retinal detachment
Retinal detachment
Retinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
and foreign fluids mechanically interacting with the photoreceptors located on the retina.
One early warning sign of Coats’ disease is yellow-eye in flash photography. Just as the red-eye effect
Red-eye effect
The red-eye effect in photography is the common appearance of red pupils in color photographs of eyes. It occurs when using a photographic flash very close to the camera lens , in ambient low light. The effect appears in the eyes of humans and animals that have no tapetum lucidum, hence no...
is caused by a reflection off blood vessels in the back of a normal eye, an eye affected by Coats’ will glow yellow in photographs as light reflects off cholesterol deposits. Children with yellow-eye in photographs are typically advised to immediately seek evaluation from an ophthalmologist, preferably a vitreo-retinal specialist.
Coats’ disease itself is painless. Pain may occur if fluid is unable to drain from the eye properly, causing the internal pressure to swell, resulting in painful glaucoma.
Pathogenesis
Coats' disease is thought to result from breakdown of the blood-retinal barrierBlood-retinal barrier
The blood–retinal barrier, or the BRB, is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina...
in the endothelial cell
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
, resulting in leakage of blood products containing cholesterol
Cholesterol
Cholesterol is a complex isoprenoid. Specifically, it is a waxy steroid of fat that is produced in the liver or intestines. It is used to produce hormones and cell membranes and is transported in the blood plasma of all mammals. It is an essential structural component of mammalian cell membranes...
crystals and lipid-laden macrophage
Macrophage
Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...
s into the retina and subretinal space. Over time, the accumulation of this proteinaceous exudate thickens the retina, leading to massive, exudative retinal detachment.
Diagnosis
On funduscopic eye examination, the retinal vessels in early Coats' disease appear tortuous and dilated, mainly confined to the peripheral and temporal portions of retina. In moderate to severe Coats' disease, massive retinal detachment and hemorrhage from the abnormal vessels may be seen.Imaging findings
Imaging studies such as ultrasonographyMedical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
(US), Computerized Tomography (CT) and Magnetic Resonance Imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI) can aid diagnosis
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
. On ultrasound, Coats' disease appears as a hyperechoic mass in the posterior vitreous without posterior acoustic shadowing; vitreous and subretinal hemorrhage may often be observed.
On CT, the globe appears hyperdense compared to normal vitreous due to the proteinaceous exudate, which may obliterate the vitreous space in advanced disease. The anterior margin of the subretinal exudate enhances with contrast. Since the retina is fixed posteriorly at the optic disc, this enhancement has a V-shaped configuration.
On MRI, the subretinal exudate shows high signal intensity on both T1- and T2-weighted images. The exudate may appear heterogeneous if hemorrhage or fibrosis is present. The subretinal space does not enhance with gadolinium contrast. Mild to moderate linear enhancement may be seen between the exudate and the remaining vitreous. The exudate shows a large peak at 1-1.6 ppm on proton MR spectroscopy
Nuclear magnetic resonance
Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...
.
Pathologic findings
Grossly, retinal detachment and yellowish subretinal exudate containing cholesterol crystals are commonly seen.Microscopically, the wall of retinal vessels may be thickened in some cases, while in other cases the wall may be thinned with irregular dilatation of the lumen. The subretinal exudate consists of cholesterol crystals, macrophages laden with cholesterol and pigment, erythrocytes, and hemosiderin
Hemosiderin
thumb|Hemosiderin image of a kidney viewed under a microscope. The brown areas represent hemosiderinHemosiderin or haemosiderin is an iron-storage complex. It is always found within cells and appears to be a complex of ferritin, denatured ferritin and other material...
. A granulomatous reaction, induced by the exudate, may be seen with the retina. Portions of the retina may develop gliosis
Gliosis
Gliosis is a proliferation of astrocytes in damaged areas of the central nervous system . This proliferation usually leads to the formation of a glial scar....
as a response to injury.
Treatment
In the early stages, there are a few treatment options. Laser surgeryLaser surgery
Laser surgery is surgery using a laser to cut tissue instead of a scalpel. Examples include the use of a laser scalpel in otherwise conventional surgery, and soft tissue laser surgery, in which the laser beam vaporizes soft tissue with high water content...
or cryotherapy
Cryotherapy
Cryotherapy is the local or general use of low temperatures in medical therapy or the removal of heat from a body part. The term "cryotherapy" comes from the Greek cryo meaning cold and the word therapy meaning cure...
(freezing) can be used to destroy the abnormal blood vessels, thus halting progression of the disease. However, if the leaking blood vessels are clustered around the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
, this treatment is not recommended as accidental damage to the nerve itself can result in permanent blindness. Although Coats’ disease tends to progress to visual loss, it may stop progressing on its own, either temporarily or permanently. Cases have been documented in which the condition even reverses itself. However, once total retinal detachment occurs, sight loss is permanent in most cases. Removal of the eye (enucleation) is an option if pain or further complications arise.
External links
- GeneReviews/NIH/NCBI/UW entry on NDP-Related Retinopathies
- http://www.orpha.net/data/patho/GB/uk-Coats.pdf
- http://www.coatsdisease.org/
- http://www.revoptom.com/handbook/41.htm