Retinopathy

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Retinopathy
Fundus retinopathy EDA03.JPG
Retinopathy in fundus of eye
Specialty Ophthalmology   OOjs UI icon edit-ltr-progressive.svg

Retinopathy is any damage to the retina of the eyes, which may cause vision impairment. [1] Retinopathy often refers to retinal vascular disease, or damage to the retina caused by abnormal blood flow. [2] Age-related macular degeneration is technically included under the umbrella term retinopathy but is often discussed as a separate entity. Retinopathy, or retinal vascular disease, can be broadly categorized into proliferative and non-proliferative types. Frequently, retinopathy is an ocular manifestation of systemic disease as seen in diabetes or hypertension. [3] Diabetes is the most common cause of retinopathy in the U.S. as of 2008. [4] Diabetic retinopathy is the leading cause of blindness in working-aged people. [5] It accounts for about 5% of blindness worldwide and is designated a priority eye disease by the World Health Organization. [6]

Contents

Signs and symptoms

Many people often do not have symptoms until very late in their disease course. Patients often become symptomatic when there is irreversible damage. [7] Symptoms are usually not painful and can include:

Pathophysiology

The development of retinopathy can be broken down into proliferative and non-proliferative types. Both types cause disease by altering the normal blood flow to the retina through different mechanisms. The retina is supplied by small vessel branches from the central retinal artery. [8] Proliferative retinopathy refers to damaged caused by abnormal blood vessel growth. [9] Normally, angiogenesis is a natural part of tissue growth and formation. When there is an unusually high or fast rate of angiogenesis, there is an overgrowth of blood vessels called neovascularization. In the non-proliferative type, abnormal blood flow to the retina occurs due to direct damage or compromise of the blood vessels themselves. Many causes of retinopathy may cause both proliferative and non-proliferative types, though some causes are more associated one type.

Non-proliferative retinopathy

Non-proliferative retinopathy is often caused by direct damage or remodeling of the small blood vessels supplying the retina. [8] Many common causes of non-proliferative damage include hypertensive retinopathy, retinopathy of prematurity, radiation retinopathy, solar retinopathy, and retinopathy associated with sickle cell disease.

There are three main mechanisms of damage in non-proliferative retinopathy: blood vessel damage or remodeling, direct retinal damage, or occlusion of the blood vessels. The first mechanism is indirect damage by altering the blood vessels that supply the retina. In the case of hypertension, high pressures in the system causes the walls of the artery to thicken, which effectively reduces the amount of blood flow to the retina. [8] This reduction in flow causes tissue ischemia leading to damage. Atherosclerosis, or hardening and narrowing of blood vessels, also reduces flow to the retina. The second mechanism is direct damage to the retina usually caused by free radicals that causes oxidative damage to the retina itself. [10] Radiation, solar retinopathy, and retinopathy of prematurity fall under this category. The third common mechanism is occlusion of blood flow. This can be caused by either physically blocking the vessels of the retinal artery branches or causing the arteries to narrow. [2] Again, the end result is reduced blood flow to the retina causing tissue damage. Sickle cell disease compromises blood flow by causing blood to sludge, or thicken and flow slowly, through the retinal arteries. Other disorders that cause hyperviscosity syndrome may also cause blood sludging. Lastly, clots or central artery thrombosis directly blocks flow to the retina causing the cells to die.

Proliferative retinopathy

Proliferative retinopathy during exam Fundus Proliferative retinopathy EDA01.JPG
Proliferative retinopathy during exam

Proliferative retinopathy is the result of aberrant blood flow to the retina due to blood vessel overgrowth, or neovascularization. These pathologically overgrown blood vessels are often fragile, weak, and ineffective at perfusing the retinal tissues. [11] These weak, fragile vessels are also often leaky, allowing fluids, protein, and other debris to leech out into the retina. They are also prone to hemorrhage due to their poor strength. This makes proliferative types of retinopathy more risky since vessel hemorrhaging often leads to vision loss and blindness. [12] Many of the causes mentioned in non-proliferative retinopathy may also cause proliferative retinopathy at later stages. Angiogenesis and neovascularization tend to be a later manifestation of non-proliferative retinopathy. Many types of non-proliferative retinopathies result in tissue ischemia or direct retinal damage. The body responds by trying to increase blood flow to damaged retinal tissues. [13] Diabetes mellitus, which causes diabetic retinopathy, is the most common cause of proliferative retinopathy in the world. [14]

Other causes

Genetic mutations are rare causes of certain retinopathies and are usually X-linked including NDP family of genes causing Norrie Disease, FEVR, and Coats disease among others. There is emerging evidence that there may be a genetic predisposition in patients who develop retinopathy of prematurity and diabetic retinopathy. [15] [16] Trauma, especially to the head, and several diseases may cause Purtscher's retinopathy.

Diagnosis

Retinopathy is diagnosed by an ophthalmologist or an optometrist during eye examination. The clinician will need to examine the retina, at the back of the eye, to make this diagnosis. There are several ways to examine the retina. The clinician can directly view the retina by looking through the pupil with a light. In most cases, the clinician will dilate the pupil to make for better visualization [17] . Stereoscopic fundus photography is the gold standard for the diagnosis of retinopathy.

Access to Care

Telemedicine programs are available that allow primary care clinics to take images using specially designed retinal imaging equipment which can then be shared electronically with specialists at other locations for review. [18] In 2009, Community Health Center, Inc. implemented a telemedicine retinal screening program for low-income patients with diabetes as part of those patients annual visits at the Federally Qualified Health Center. [19]

Prevention

Retinopathy is often secondary to diseases such as diabetes or hypertension. Controlling blood sugar levels and blood pressure have been shown to help decrease incidence of retinopathy.

Blood sugar control: If someone has diabetes, or is at high risk for diabetes, it is important for them to have their blood sugar levels checked. The gold standard blood sugar test is the A1C test. Many studies have suggested that lowering A1C levels in someone with elevated A1C levels can lower the incidence and progression of retinopathy. Fortunately, blood sugar control can have benefits beyond just the eye. A primary care physician can help with blood sugar control strategies.

Blood pressure control: Controlling blood pressure can also lower the incidence and progression of retinopathy. A primary care physician can help with blood pressure control strategies.

Other: Besides blood sugar and blood pressure control, there are other modifications that can help. Regular exercise may help lower the incidence and progression of retinopathy. If someone have sleep apnea, treatment of sleep apnea may help as well.

Treatment

Treatment is based on the cause of the retinopathy and may include laser therapy to the retina. Laser photocoagulation therapy has been the standard treatment for many types of retinopathy. Evidence shows that laser therapy is generally safe and improves visual symptoms in sickle cell and diabetic retinopathy. [20] [21] In recent years targeting the pathway controlling vessel growth or angiogenesis has been promising. Vascular endothelial growth factor (VEGF) seems to play a vital role in promoting neovascularization. Using anti-VEGF drugs (antibodies to sequester the growth factor), research have shown significant reduction in the extent of vessel outgrowth. Evidence supports the use of anti-VEGF antibodies, such as bevacizumab or pegaptanib, seems to improve outcomes when used in conjunction with laser therapy to treat retinopathy of prematurity. [22] [ needs update ] The evidence is poorer for treatment of diabetic retinopathy. Use of anti-VEGF drugs did not appear to improve outcomes when compared to standard laser therapy for diabetic retinopathy. [23]

Epidemiology

The two most common causes of retinopathy include diabetic retinopathy and retinopathy of prematurity. Diabetic retinopathy affects about 5 million people and retinopathy of prematurity affect about 50,000 premature infants each year worldwide. [6] [24] Hypertensive retinopathy is the next most common cause affecting anywhere from 3 to 14% of all non-diabetic adults. [25]

See also

Related Research Articles

The following is a glossary of diabetes which explains terms connected with diabetes.

Angiopathy is the generic term for a disease of the blood vessels. The best known and most prevalent angiopathy is diabetic angiopathy, a common complication of chronic diabetes.

Diabetic retinopathy Human disease

Diabetic retinopathy, also known as diabetic eye disease, is a medical condition in which damage occurs to the retina due to diabetes mellitus. It is a leading cause of blindness in developed countries.

Hypertensive retinopathy Human disease

Hypertensive retinopathy is damage to the retina and retinal circulation due to high blood pressure.

Microangiopathy is an angiopathy affecting small blood vessels in the body. It can be contrasted to macroangiopathy, or large vessel disease.

Vitrectomy surgery to remove some or all of the vitreous humor from the eye

Vitrectomy is a surgery to remove some or all of the vitreous humor from the eye.

Retinopathy of prematurity (ROP), also called retrolental fibroplasia (RLF) and Terry syndrome, is a disease of the eye affecting prematurely born babies generally having received intensive neonatal care, in which oxygen therapy is used on them due to the premature development of their lungs. It is thought to be caused by disorganized growth of retinal blood vessels which may result in scarring and retinal detachment. ROP can be mild and may resolve spontaneously, but it may lead to blindness in serious cases. As such, all preterm babies are at risk for ROP, and very low birth-weight is an additional risk factor. Both oxygen toxicity and relative hypoxia can contribute to the development of ROP.

Macular edema Human disease

Macular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell (edema). The swelling may distort a person's central vision, because the macula holds tightly packed cones that provide sharp, clear, central vision to enable a person to see detail, form, and color that is directly in the centre of the field of view.

Fluorescein angiography technique for examining the circulation of the retina and choroid of the eye

Fluorescein angiography (FA), fluorescent angiography (FAG), or fundus fluorescein angiography (FFA) is a technique for examining the circulation of the retina and choroid using a fluorescent dye and a specialized camera. Sodium fluorescein is added into the systemic circulation, the retina is illuminated with blue light at a wavelength of 490 nanometers, and an angiogram is obtained by photographing the fluorescent green light that is emitted by the dye. The fluorescein is administered intravenously in intravenous fluorescein angiography (IVFA) and orally in oral fluorescein angiography (OFA). The test is a dye tracing method.

Retinal haemorrhage is a disorder of the eye in which bleeding occurs in the retina, the light sensitive tissue, located on the back wall of the eye. There are photoreceptor cells in the retina called rods and cones, which transduce light energy into nerve signals that can be processed by the brain to form visual images. Retinal hemorrhage can affect adults, and newborn babies and infants may also suffer from this disorder.

Eales disease is a type of obliterative vasculopathy, also known as angiopathia retinae juvenilis, periphlebitis retinae, primary perivasculitis of the retina. It was first described by the British ophthalmologist Henry Eales (1852–1913) in 1880 and is a rare ocular disease characterized by inflammation and possible blockage of retinal blood vessels, abnormal growth of new blood vessels (neovascularization), and recurrent retinal and vitreal hemorrhages. This disease is identified by its three characteristic steps: vasculitis, occlusion, and retinal neovascularization, leading to recurrent vitreous hemorrhages and vision loss. Eales Disease with a characteristic clinical picture, fluorescein angiographic finding, and natural course is considered a specific disease entity. The exact cause of this disease is unknown but it appears to affect individuals that are from Asian subcontinents. This disease tends to begin between the ages of 20-30 years and begins with unilateral peripheral retinal perivasculitis and peripheral retinal capillary non-perfusion. These are not normally recognized until the inflammation results in vitreous hemorrhage. This disease has been found to affect the second eye 50-90% of the time so there is a large chance that both eyes will begin to show signs of the disease.

Rubeosis iridis, is a medical condition of the iris of the eye in which new abnormal blood vessels are found on the surface of the iris.

Ocular ischemic syndrome is the constellation of ocular signs and symptoms secondary to severe, chronic arterial hypoperfusion to the eye. Amaurosis fugax is a form of acute vision loss caused by reduced blood flow to the eye; it may be a warning sign of an impending stroke, as both stroke and retinal artery occlusion can be caused by thromboembolism due to atherosclerosis elsewhere in the body. Consequently, those with transient blurring of vision are advised to urgently seek medical attention for a thorough evaluation of the carotid artery. Anterior segment ischemic syndrome is a similar ischemic condition of anterior segment usually seen in post-surgical cases. Retinal artery occlusion leads to rapid death of retinal cells, thereby resulting in severe loss of vision.

Cotton wool spots

Cotton wool spots are an abnormal finding on funduscopic exam of the retina of the eye. They appear as fluffy white patches on the retina. They are caused by damage to nerve fibers and are a result of accumulations of axoplasmic material within the nerve fiber layer. There is reduced axonal transport within the nerves because of the ischemia. This then causes the nerve fibers to be damaged by swelling in the surface layer of the retina. A 1981 analysis concluded that "in most instances, cotton-wool spots do not represent the whole area of ischaemic inner retina but merely reflect the obstruction of axoplasmic flow in axons crossing into much larger ischaemic areas". Associated findings include microvascular infarcts and hemorrhages. The appearance of cotton wool spots may decrease over time. Abundant cotton wool spots are seen in Malignant hypertension.

Choroidal neovascularization

Choroidal neovascularization (CNV) is the creation of new blood vessels in the choroid layer of the eye. Choroidal neovascularization is a common cause of neovascular degenerative maculopathy commonly exacerbated by extreme myopia, malignant myopic degeneration, or age-related developments.

Central retinal vein occlusion Human disease

The central retinal vein is the venous equivalent of the central retinal artery and, like that blood vessel, it can suffer from occlusion, similar to that seen in ocular ischemic syndrome. Since the central retinal artery and vein are the sole source of blood supply and drainage for the retina, such occlusion can lead to severe damage to the retina and blindness, due to ischemia and edema (swelling).

Laser coagulation or laser photocoagulation surgery is used to treat a number of eye diseases and has become widely used in recent decades. During the procedure, a laser is used to finely cauterize ocular blood vessels to attempt to bring about various therapeutic benefits.

Intraretinal microvascular abnormalities

Intraretinal microvascular abnormalities (IRMA) are abnormalities of the blood vessels that supply the retina of the eye, a sign of diabetic retinopathy. IRMA can be difficult to distinguish from and is likely a precursor to retinal neovascularization. One way to distinguish IRMA from retinal neovascularization is to perform fluorescein angiography. Since IRMA blood vessels are patent, unlike neovascular vessels, they do not leak, and therefore exhibit hyperfluorescence on fluorescein angiography.

Vitreous hemorrhage

Vitreous hemorrhage is the extravasation, or leakage, of blood into the areas in and around the vitreous humor of the eye. The vitreous humor is the clear gel that fills the space between the lens and the retina of the eye. A variety of conditions can result in blood leaking into the vitreous humor, which can cause impaired vision, floaters, and photopsia.

Radiation retinopathy

Radiation retinopathy is damage to retina due to exposure to ionizing radiation. Radiation retinopathy has a delayed onset, typically after months or years of radiation, and is slowly progressive. In general, radiation retinopathy is seen around 18 months after treatment with external-beam radiation and with brachytherapy. The time of onset of radiation retinopathy is between 6 months to 3 years.

References

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