Radiation retinopathy

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Radiation retinopathy
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Radiation retinopathy [1]
Specialty Ophthalmology

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. [2]

Retina light-sensitive organ in the eye

The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception, the retina serving a function analogous to that of the film or image sensor in a camera.

Ionizing radiation Radiation that carries enough light energy to liberate electrons from atoms or molecules

Ionizing radiation is radiation that carries sufficient energy to detach electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic subatomic particles, ions or atoms moving at high speeds, and electromagnetic waves on the high-energy end of the electromagnetic spectrum.

Contents

An exposure to doses of 30-35 grays (Gy) or more is usually required to induce clinical symptoms, however, retinopathy may develop after as little as 15 Gy of external-beam radiation. A reported safe dose is 30 Gy (3,000 rad): 10 Gy (1,000 rad) per week in five fractions of 2 Gy (200 rad). [1]

The gray is a derived unit of ionizing radiation dose in the International System of Units (SI). It is defined as the absorption of one joule of radiation energy per kilogram of matter.

Signs and symptoms

Clinically, affected people may not have symptoms or may complain of decreased visual acuity. Ophthalmic examination may reveal signs of retinal vascular disease, including cotton-wool spots, retinal bleeds, microaneurysms, perivascular sheathing, capillary telangiectasis, macular edema, and disc edema. Capillary non perfusion, documented by fluorescein angiography, is commonly present, and extensive retinal ischemia can lead to neovascularization of the retina, iris, and disc. Staging of radiation retinopathy has been proposed. [3]

Edema abnormal accumulation of fluid in the interstitium

Edema, also spelled oedema or œdema, is an abnormal accumulation of fluid in the interstitium, located beneath the skin and in the cavities of the body, which can cause severe pain. Clinically, hyperaldosteronism, edema manifests as swelling. The amount of interstitial fluid is determined by the balance of fluid homeostasis and the increased secretion of fluid into the interstitium. The word is from Greek οἴδημα oídēma meaning "swelling". The condition is also known as dropsy.

Fluorescein angiography

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.

Ischemia restriction in blood supply to tissues, causing a shortage of oxygen and glucose

Ischemia or ischaemia is a restriction in blood supply to tissues, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue. It also means local anemia in a given part of a body sometimes resulting from constriction. Ischemia comprises not only insufficiency of oxygen, but also reduced availability of nutrients and inadequate removal of metabolic wastes. Ischemia can be partial or total.

Pathophysiology

Radiation retinopathy is very similar to other vascular diseases. Diabetes and radiation primarily damage the retinal capillaries. Diabetes results in early loss of pericytes and thickening of the basement membrane. Radiation however, damages the endothelial cells.

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.

Pericyte contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body

Pericytes are multi-functional mural cells of the microcirculation that wrap around the endothelial cells that line the capillaries and venules throughout the body. Pericytes are embedded in basement membrane where they communicate with endothelial cells of the body's smallest blood vessels by means of both direct physical contact and paracrine signaling. Pericytes help to maintain homeostatic and hemostatic functions in the brain and also sustain the blood–brain barrier. These cells are also a key component of the neurovascular unit, which includes endothelial cells, astrocytes, and neurons. Pericytes regulate capillary blood flow, the clearance and phagocytosis of cellular debris, and the permeability of the blood–brain barrier. Pericytes stabilize and monitor the maturation of endothelial cells by means of direct communication between the cell membrane as well as through paracrine signaling. A deficiency of pericytes in the central nervous system can cause the blood–brain barrier to break down.

Diagnosis

Treatment

The management of radiation retinopathy is similar to that for diabetic retinopathy and includes focal laser therapy to reduce macular edema or panretinal photocoagulation to treat zones of ischemia and neovascularization. Anti-vascular endothelial growth factors have been recently used for the treatment of radiation retinopathy. [4] Monitoring of visual acuity in all cases and early referral to the ophthalmologist is warranted.

Vascular endothelial growth factor (VEGF), originally known as vascular permeability factor (VPF), is a signal protein produced by cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, the platelet-derived growth factor family of cystine-knot growth factors. They are important signaling proteins involved in both vasculogenesis and angiogenesis.

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Retinopathy eye disease that is located in the retina

Retinopathy is any damage to the retina of the eyes, which may cause vision impairment. Retinopathy often refers to retinal vascular disease, or damage to the retina caused by abnormal blood flow. 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. Diabetes is the most common cause of retinopathy in the U.S. as of 2008. Diabetic retinopathy is the leading cause of blindness in working-aged people. It accounts for about 5% of blindness worldwide and is designated a priority eye disease by the World Health Organization.

Hypertensive retinopathy Human disease

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

The National Eye Institute (NEI) was established in 1968 and is located in Bethesda, Maryland. The NEI is one of 27 institutes and centers of the US National Institutes of Health (NIH), an agency of the US Department of Health and Human Services. The mission of NEI is to prolong and protect the vision of the American people. The NEI conducts and performs research into treating and preventing diseases affecting the eye or vision.

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.

Central serous retinopathy

Central serous retinopathy (CSR), also known as central serous chorioretinopathy, is an eye disease that causes visual impairment, often temporary, usually in one eye. When the disorder is active it is characterized by leakage of fluid under the retina that has a propensity to accumulate under the central macula. This results in blurred or distorted vision (metamorphopsia). A blurred or gray spot in the central visual field is common when the retina is detached. Reduced visual acuity may persist after the fluid has disappeared.

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.

Optic neuropathy is damage to the optic nerve from any cause. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy. The main symptom is loss of vision, with colors appearing subtly washed out in the affected eye. On medical examination, the optic nerve head can be visualised by an ophthalmoscope. A pale disc is characteristic of long-standing optic neuropathy. In many cases, only one eye is affected and patients may not be aware of the loss of color vision until the doctor asks them to cover the healthy eye.

Presumed ocular histoplasmosis syndrome Human disease

Presumed ocular histoplasmosis syndrome (POHS) is a syndrome affecting the eye, which is characterized by peripheral atrophic chorioretinal scars, atrophy or scarring adjacent to the optic disc and maculopathy.

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.

Optic pit Human disease

Optic pit, optic nerve pit, or optic disc pit is a congenital excavation of the optic disc, resulting from a malformation during development of the eye. Optic pits are important because they are associated with posterior vitreous detachments (PVD) and even serous retinal detachments.

The PASCAL Photocoagulator is an integrated semi-automatic pattern scan laser photocoagulation system designed to treat ocular diseases using a single shot or predetermined pattern array. The device is for ophthalmologists, particularly those that focus in vitreo-retinal surgery, a type of eye surgery. It was developed by OptiMedica, an ophthalmic medical device company located in Silicon Valley.

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).

Macular telangiectasia condition of the retina

Macular telangiectasia describes two distinct retinal diseases affecting the macula of the eye, macular telangiectasia type 1 and macular telangiectasia type 2.

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.

Gholam A. Peyman is an ophthalmologist, retina surgeon, and inventor. He is best known for his invention of LASIK eye surgery, a vision correction procedure designed to allow people to see clearly without glasses. He was awarded the first US patent for the procedure in 1989.

Branch retinal vein occlusion Human disease

Branch retinal vein occlusion (BRVO) is a common retinal vascular disease of the elderly. It is caused by the occlusion of one of the branches of central retinal vein.

Joan W. Miller is a Canadian-American ophthalmologist and scientist who has made notable contributions to the treatment and understanding of eye disorders. She is credited for developing photodynamic therapy (PDT) with verteporfin (Visudyne), the first pharmacologic therapy for retinal disease. She also co-discovered the role of vascular endothelial growth factor (VEGF) in eye disease and demonstrated the therapeutic potential of VEGF inhibitors, forming the scientific basis of anti-VEGF therapy for age-related macular degeneration (AMD), diabetic retinopathy, and related conditions.

John Marshall (eye laser scientist)

John Marshall MBE, FMedSci, PhD, DSc, FRCPath, FRSB, FRCOphth(Hon), FRCOptom(Hon), FARVO is a British medical scientist and inventor. Currently he is the Frost Professor of Ophthalmology at the Institute of Ophthalmology UCL and Emeritus Professor King's College London. He is a pioneer of laser eye surgery.

References

  1. 1 2 Gupta, Abha; Dhawahir-Scala, Felipe; Smith, Amy; Young, Lorna; Charles, Steve (1 January 2007). "Radiation Retinopathy: Case report and review". BMC Ophthalmology. 7 (1): 6. doi:10.1186/1471-2415-7-6.
  2. ↑ American Academy of Ophthalmology (2012). Retina and vitreous (2011-2012 ed.). ISBN   9781615251193.
  3. ↑ Finger, PT; Kurli, M (Jun 2005). "Laser photocoagulation for radiation retinopathy after ophthalmic plaque radiation therapy". The British Journal of Ophthalmology. 89 (6): 730–8. doi:10.1136/bjo.2004.052159. PMC   1772675 . PMID   15923510.
  4. ↑ Finger, PT; Mukkamala, SK (Jul–Aug 2011). "Intravitreal anti-VEGF bevacizumab (Avastin) for external beam related radiation retinopathy". European Journal of Ophthalmology. 21 (4): 446–51. doi:10.5301/EJO.2011.6213. PMID   21218391.
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