Glossary of Eye Conditions

Use our glossary as a quick reference to learn about different eye conditions and common terms used when describing them. The glossary is alphabetized to make it easier for you to find the information you need.

ABCD – E – FGH – I – J – KLMN
OP – Q – RSTUV – W – X – Y – Z



Rare, inherited vision disorder in which a person has little or no ability to see color. People with achromatopsia also commonly experience low vision, especially in bright light, to which they are extremely sensitive. The severity of achromatopsia varies. Although there is no cure or treatment for this disorder, people with achromatopsia can manage its symptoms. For example, they can wear sunglasses or tinted contact lenses to cope with bright light. They can use magnifiers and other devices for low vision to help them read, and telescopes to help them see distant objects.

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Acute Zonal Occult Outer Retinopathy (AZOOR)

Acute zonal occult outer retinopathy (AZOOR) is a retinal disease characterized by the sudden onset of flashing lights and visual field changes in an individual with a normal retinal exam. It affects women 3 times more frequently than men; most people affected are Caucasian, middle-aged, and myopic. A viral illness has preceded many of the reported cases. Initially, only one eye is involved but the other eye may be affected months to years later.

Age-related macular degeneration (ARMD)

See macular degeneration.

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Age-Related Macular Degeneration


A hereditary condition characterized by a variable lack of pigment in the eyes, skin, or hair. People with albinism may have pale pink skin and blond to white hair, but there are different types of albinism, and the amount of pigment varies. The irises of their eyes may be white or pinkish. They are sensitive to bright light and glare and commonly have other vision problems. While some people with albinism can see well enough to drive, many have low vision or may even be legally blind. Albinism is often accompanied by nystagmus or strabismus. People with albinism are sensitive to bright light and glare and may wear tinted eyeglasses. Bifocals, magnifiers, and other optical devices can help people with albinism.

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A condition in which a person’s vision does not develop properly in early childhood because the eye and brain do not work together correctly. Amblyopia, which usually affects only one eye, is also known as “lazy eye.” A person with amblyopia experiences blurred vision in the affected eye. However, children often do not complain of blurred vision in the amblyopic eye because it seems normal to them. Early treatment is advisable because, if left untreated, this condition may lead to permanent vision problems. Treatment options include vision therapy exercises or prescription eyeglasses. People with amblyopia may need an eye patch over their stronger eye to force the affected eye to function as it should.

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Partial or complete absence of the iris of the eye. This rare condition, usually present at birth, results in low vision and sensitivity to light. People with aniridia are also at high risk for other eye conditions, such as glaucoma, nystagmus, and cataracts. People with aniridia may benefit from wearing tinted contact lenses or sunglasses, using magnifiers, and avoiding intense or glaring light.

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A rare condition in which one or both eyes do not form during pregnancy. When both eyes are affected, blindness results. There is no cure for anophthalmia. Prosthetic eyes can promote proper growth of the eye sockets and development of facial bones and also serve cosmetic purposes.

Suggested resource: Anophthalmia and Microphthalmia | National Eye Institute (


Absence of the lens of the eye. Aphakia is usually associated with the surgical removal of a cataract but may also result from a wound or other cause. Without the lens, the eye cannot adjust its focus to see at different distances. Contact lenses or eyeglasses are used to correct the vision of someone with aphakia. In cataract surgery, an artificial lens is inserted to replace the lens removed. A person with aphakia will benefit from good, but not excessive, lighting and high-contrast reading materials.

Suggested resource: What Is Aphakia? – American Academy of Ophthalmology (


Common vision condition, usually present from birth, caused by an irregularly curved cornea or lens. People with astigmatism may experience blurred vision, eyestrain, or headaches. Two-thirds of Americans who have myopia also have astigmatism. Astigmatism can be corrected with eyeglasses or contact lenses. Corrective surgery is another option.

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Best’s Disease

A rare, inherited condition that affects the macula, the area in the middle of the retina, can cause blurred or distorted vision or a loss of central vision. Best’s Disease, also known as Vitelliform Macular Dystrophy, may affect both eyes. The disease’s effects on sight vary and may not become severe for many years, if ever. Most people are not significantly affected until after age 40. There is no treatment for Best’s Disease, but a person whose vision is impaired by this disease may benefit from devices for low vision.

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A condition in which the lens of the eye, which is normally clear, becomes cloudy or opaque. Cataracts generally form slowly and without pain. They can affect one or both eyes. Over time, a cataract may interfere with vision, causing images to appear blurred or fuzzy and colors to seem faded. Most cataracts are related to aging. Cataracts affect more than 50 percent of all adults by age 80 and are the primary cause of vision loss in people 55 and older. People with early cataracts may benefit from new eyeglasses, bright lighting, anti-glare sunglasses, or magnifying lenses. If, despite such devices, cataract interferes with daily activities, surgery is the only effective treatment. Cataract surgery, which is common, involves the removal of the cloudy lens and replacement with an artificial lens.

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Charles Bonnet syndrome

Visual disturbances usually occur in people who have experienced low vision or sight loss later in life, as through macular degeneration. People with Charles Bonnet syndrome may see a wide range of images, from simple patterns to people, animals, and buildings. The visual disturbances associated with this syndrome are not signs of mental illness, and people realize that the images they see are not real. There is no cure for Charles Bonnet syndrome. However, the symptoms often stop on their own. People who have Charles Bonnet syndrome should consult with an eye care specialist because treatment for vision disorders may help.

Suggested resources:
Charles Bonnet Syndrome

Chorioretinal Atrophy

Chorioretinal atrophy is, as the name implies, a degeneration or atrophy of the retina. It affects males more than females. It is an autosomal dominant disorder caused by mutations in the CRB1 gene.

Choroidal Neovascularization

Choroidal neovascularization refers to new and abnormal blood vessels that grow, multiply, and develop into a cluster beneath the macula. The macula is the part of the retina that provides the clearest central vision.


Choroideremia is a rare disorder that causes progressive loss of the choroid, a critical layer under the retina responsible for some of its blood supply. Choroideremia is an inherited disorder that generally affects males only. It commonly begins as night blindness in childhood and gradually advances to increasing low vision. Most people with this disorder can retain good vision until age 40 or 50. There is no treatment for choroideremia, but people with the disorder may find it helpful to use optical, electronic, or computer-based devices for low vision.

Suggested resource: Choroideremia Research Foundation


A cleft or gap in some part of the eye, such as the iris, lens, or retina, is caused by a defect in the development of the eyeball. How much coloboma affects a person’s vision depends on the size and location of the cleft and on whether it occurs in one or both eyes. For example, someone with only a tiny defect in the iris may have normal vision. However, a person with large retina and optic nerve defects may have limited vision. Children whose vision is impaired by coloboma may benefit from reading materials with large black print and well-spaced letters and words. They may also find reading one line at a time with a cutout reading window helpful.

Suggested resource: What Is a Coloboma? – American Academy of Ophthalmology (

Color blindness

A vision problem in which a person has difficulty distinguishing specific colorsā€”most commonly red and green, but sometimes blue and green or blue and yellow. Color blindness is not a form of blindness but rather a deficiency in color perception. It usually affects both eyes and is much more common in males than females. There is no treatment or cure for this problem, but a color-blind person can learn to adapt in various ways. For example, a color-blind driver can remember that the light positioned at the top of a traffic light is red. It is beneficial to diagnose color blindness in children at an early age so that steps can be taken to avoid learning problems related to color perception.

Suggested resource: What Is Color Blindness? – American Academy of Ophthalmology (

Cone-rod dystrophy

An inherited disease that, over time, causes deterioration of the specialized light-sensitive cells of the retina. People with cone-rod dystrophy typically experience decreased sharpness of vision followed by a loss of peripheral vision and color perception. The most common form of cone-rod dystrophy is retinitis pigmentosa. There is no treatment or cure for this disease, also called cone-rod degeneration, progressive cone-rod dystrophy, and retinal cone dystrophy.

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Congenital eye defects

Any of various conditions present at birth that affect the eyes or vision. Some congenital eye conditions, such as retinitis pigmentosa, are passed on through genes. Others, such as vision loss due to German measles, result from a disease or deficiency during pregnancy. Sometimes, as in the case of coloboma, the cause of a congenital eye defect is unknown. Congenital eye defects can impair vision or even cause blindness. Some conditions are immediately apparent in an infant, while others may not be known later in life. Conjunctivitis is inflammation of the conjunctiva, which is the thin translucent tissue that lines the inner surface of the eyelid and the outer surface of the sclera, which is the white part of the eye.

Conjunctivitis is usually associated with redness of the white part of the eyes, light sensitivity (photophobia), excessive tearing, ocular discomfort (gritty sensation, itching, burning), and/or discharge.

There are many different causes of conjunctivitis. Some types of conjunctivitis are infectious, while others are not. These can generally be differentiated from one another based on history and an examination by an eye doctor.

Suggested Resource: Conjunctivitis

Corneal disease

Disease or disorder that affects the cornea, the clear, curved surface that covers the front of the eye. The effects of corneal disease vary. Some corneal conditions cause few, if any, vision problems. For example, infections of the cornea can often be treated with antibiotics. However, if the cornea becomes cloudy, light cannot penetrate the eye to reach the retina, and severe low vision, or even blindness, may result. Corneal dystrophies are usually inherited conditions in which one or more parts of the cornea lose their clarity due to a buildup of cloudy material. Keratoconus is the most common corneal dystrophy in the United States. When corneal disease causes the cornea to become permanently clouded or scarred, doctors may be able to restore vision with a corneal transplantā€”surgical replacement of the old cornea with a new one.

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Cortical visual impairment

Visual impairment is caused by damage to those parts of the brain related to vision. Although the eye is normal, the brain cannot properly process the information it receives. The degree of low vision may be mild or severe and can vary greatly, even daily. Also known as cerebral visual impairment, cortical visual impairment (CVI) may be temporary or permanent. People with cortical visual impairment have difficulty using what their eye sees. For example, they may have trouble recognizing faces, interpreting drawings, perceiving depth, or distinguishing between background and foreground. Children with cortical visual impairment can often see better when told in advance what to look for. Cortical visual impairment is also known as neurological visual impairment (NVI).

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De Morsier’s Syndrome

A rare disorder present at birth, in which the optic nerve is underdeveloped, the pituitary gland does not function properly, and often a portion of brain tissue is not formed. De Morsier’s Syndrome, also known as septo-optic dysplasia, may cause blindness in one or both eyes and is often accompanied by nystagmus and other symptoms. Some children with De Morsier’s Syndrome have normal intelligence, while others may be developmentally delayed, have learning disabilities, or have cognitive impairments. Some symptoms of this disorder can be treated, but low vision usually cannot be corrected. Visual devices, such as a magnifier or a computer designed for low-vision users, may benefit some people with De Morsier’s Syndrome. Diabetic retinopathy Eye condition that results from the damaging effect of diabetes on the circulatory system of the retina. The longer someone has had diabetes, the greater the person’s likelihood of developing diabetic retinopathy. Changes in the retina’s tiny blood vessels can lead to low vision. People with diabetes should have routine eye examinations to diagnose and treat diabetes-related problems as soon as possible. Maintaining strict control of blood sugar levels helps to prevent diabetic retinopathy. Surgical and laser treatments can help many people affected by this condition.

Suggested resources:
Diabetes and Diabetic Retinopathy
Diabetic Retinopathy | National Eye Institute (

Dry eye syndrome

Persistent dryness of the eyes resulting from too little production of tears or too rapid evaporation of tears. People with dry eye syndrome may experience itching, burning, or stinging eyes. Some people feel something is caught in their eye. Dry eye syndrome has many causes. For example, it may be linked to wearing contact lenses for long periods or living in a dry or dusty climate. It may be a side effect of medication or a symptom of certain diseases. An eye doctor may recommend the application of special eye dropsā€””artificial tears”ā€”to moisten the eyes or use a humidifier to increase humidity in the air. Not rubbing the eyes and avoiding irritants like tobacco smoke can also help people with dry eye syndrome.

Suggested resource: Dry Eyes on VisionAware

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Floaters and spots

Specks or strands that seem to float across the field of vision. Floaters and spots are shadows on the retina cast by tiny bits of gel or cells inside the clear fluid that fills the eye. Floaters and spots usually are normal and harmless. However, in some cases, they may warn of serious conditions such as retinal detachment, diabetic retinopathy, or infection. Someone who experiences a sudden decline in vision accompanied by flashes and floaters or a sudden increase in the number of floaters should consult an ophthalmologist urgently.

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Disease in which the pressure of the fluid inside the eye is too high, resulting in a loss of peripheral vision. If the condition is not diagnosed and treated, the increased pressure can damage the optic nerve and eventually lead to blindness. Vision lost as a result of such damage cannot be restored. A person with glaucoma may not realize it initially, because the disease often progresses with no symptoms or warning signs. Early detection through regular eye examination and prompt treatment is essential to prevent vision loss. Daily medication (usually eye drops), surgery, or a combination of both enables most people to control their intraocular pressure and retain their vision.

Suggested resources:
Visual Impairment and Glaucoma

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Blindness affects half of the field of vision. Hemianopia, also known as hemianopsia, may be caused by various medical conditions but usually results from a stroke or brain injury. It may affect the visual field’s right or left side and is usually permanent. Hemianopia can produce various effects, from minor to severe. For example, a person may be able to see only to one side when looking ahead, or objects that the person sees may differ in clarity or brightness. Such low vision can make it difficult to perform daily tasks, from reading to crossing streets. There is no specific treatment for hemianopia, but low-vision rehabilitation specialists can help people learn to make the most of their sight. In addition, some people with hemianopia benefit from using magnifiers or special prism lenses.

Suggested resources: Stroke/Hemianopsia – ConnectCenter (


This common vision problem, also known as farsightedness, occurs when light rays enter the eye focus behind the retina, not directly on it. People with hyperopia can usually see distant objects well, but close objects appear blurry. Hyperopia may cause eyestrain or headaches, especially with reading. Eyeglasses or contact lenses can correct hyperopia. Laser vision correction is sometimes possible for people who do not want to wear glasses or contact lenses.

Suggested resource: Farsightedness: What Is Hyperopia? – American Academy of Ophthalmology (

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A rare condition, often inherited, in which the cornea becomes progressively thinner and gradually bulges outward, causing blurred or distorted vision. Keratoconus usually affects both eyes. At first, people with this condition can correct their sight with eyeglasses. However, as symptoms worsen, specially designed contact lenses are needed to improve vision. Most people with keratoconus will not experience severe low vision. However, as many as one in five will eventually require a corneal transplant (surgical replacement of the old cornea with a new one).

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Late-Onset Retinal Degeneration (L-ORD)

A genetic retinal disorder. Onset typically occurs in a person’s fifth to sixth decade. Symptoms include night blindness, progressing to severe central and peripheral degeneration with choroidal neovascularization and chorioretinal atrophy. Because it is late onset, it is often mistaken for regular macular degeneration. Note, however, that this disorder, in its severest state, affects both central and peripheral vision and thus leads to total blindness, unlike some more common macular disorders. Laurence-Moon-Bardet-Biedl Syndrome is Rare an inherited disorder affecting many parts of the body. People with this condition have retinitis pigmentosa accompanied by mental retardation, paralysis of the legs, and various other symptoms.

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Leber’s congenital amaurosis

Leber’s congenital amaurosis is an Inherited condition, probably caused by retina degeneration, in which an infant is born blind or develops severe vision loss soon after birth. Children with Leber’s congenital amaurosis typically have nystagmus, and some have mental retardation and hearing disorders. At present, there is no treatment for this condition.

Suggested resources:
Foundation for Retinal Research

Legal blindness

A level of visual impairment defined by law to determine eligibility for benefits. It refers to central visual acuity of 20/200 or less in the better eye with the best possible correction or a visual field of 20 degrees or less.

Low vision

Vision loss may be severe enough to impede a person’s ability to carry on everyday activities but still allows some functionally useful sight. Macular degeneration, cataracts, glaucoma, or other eye conditions or diseases may cause low vision. Low vision may range from moderate impairment to near-total blindness. Eyeglasses, contact lenses, or surgery cannot fully correct it. However, a person with low vision may benefit from various available optical devices, such as electronic magnifying glasses or eyeglass-mounted telescopes. In addition, special software developed for computer users with low vision can display type in large size or read text aloud.

Suggested resource: What Is Low Vision? – ConnectCenter (

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Macular degeneration

A disease that causes dysfunction of the macula, the area in the middle of the retina that makes possible the sharp central vision needed for such everyday activities as reading, driving, and recognizing faces and colors. The condition is commonly known as age-related macular degeneration (AMD) and is the leading cause of low vision among older people. However, there are also other types of macular degeneration, such as Stargardt’s Disease and Best’s Disease. Macular degeneration causes blurred, distorted, or dim vision or a blind spot in the center of the visual field. Peripheral vision is generally not affected. This condition is painless and may progress so gradually that the affected person at first notices little change. There is no cure for macular degeneration, but drug therapy, laser surgery, or other medical treatment may sometimes slow the disease’s progression or prevent further vision loss. People with macular degeneration can also benefit from using various low-vision devices, such as magnifiers, high-intensity lamps, and pocket-sized telescopes.

Suggested resources:
Age-related Macular Degeneration (AMD)

Macular hole

A macular hole is a full-thickness hole in the central part of the retina called the macula. It may be caused by injury or inflammatory swelling of the retina but most commonly occurs as an age-related event without any predisposing conditions. Macular holes are thought to be caused by tractional forces associated with the vitreous gel separating from the retina in the macula and around the central macula called the fovea. Surgery is the treatment of choice for full-thickness macular holes.

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Macular Hole

Marfan Syndrome

Disorder of the connective tissue affects the heart and blood vessels, skeletal system, eyes, and other parts of the body. The condition is present at birth. Symptoms vary from person to person, ranging from mild to severe. People with Marfan syndrome are often nearsighted (see myopia), and about half have dislocated one or both eye lenses. There is no cure for Marfan syndrome. Treatment depends on which body systems are affected. Early eye examinations can detect vision problems related to the disorder, which can usually be corrected with eyeglasses, contact lenses, or eye surgery.

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Rare disorder, usually inherited, in which one or both eyes are abnormally small. The degree of vision varies, from reduced vision to blindness. Extreme microphthalmia resembles some forms of anophthalmia. There is no treatment or cure for microphthalmia. In some instances, artificial eyes can be used to promote proper growth of the eye sockets and to help with cosmetic appearance.

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This condition, commonly known as nearsightedness, occurs when light rays enter the eye focus in front of the retina, not directly on it. People with myopia can usually see close objects well, but objects in the distanceā€”such as highway signs or writing on a chalkboardā€”appear blurred. People with this condition may squint to see distant objects and experience eyestrain or, sometimes, headaches. Eyeglasses or contact lenses can correct myopia. Surgery is another alternative.

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Neurological visual impairment (NVI)

See cortical visual impairment.

Neuromyelitis optica (NMO)

Neuromyelitis optica (NMO), also known as Devic’s disease, is an autoimmune disorder in which immune system cells and antibodies mistakenly attack and destroy myelin cells in the optic nerves (neuritis) and the spinal cord (myelitis). NMO leads to the loss of myelin, a fatty substance that surrounds nerve fibers and helps nerve signals move from cell to cell. The syndrome can cause blindness in one or both eyes and can be followed by varying degrees of paralysis in the arms and legs. Most individuals with the syndrome experience clusters of attacks months or years apart, followed by partial recovery during periods of remission. The onset of NMO varies from childhood to adulthood, with two peaks, one in childhood and the other in adults in their 40s. The syndrome is sometimes confused with multiple sclerosis (MS) because both can cause optic neuritis and myelitis attacks.

Non-24-Hour Sleep-Wake Disorder (Non-24)

Non-24-Hour Sleep-Wake Disorder (Non-24) is a serious, chronic, and rare circadian rhythm disorder that affects most totally blind individuals who lack light perception and cannot reset their master body clocks to the 24-hour day. Non-24 is most commonly found in blind individuals who cannot perceive light, the primary environmental cue for synchronizing their circadian rhythm to the 24-hour day. In the United States, this disorder affects approximately 80,000 totally blind individuals who lack the light sensitivity to reset their internal “body clocks.” Individuals with Non-24 suffer from various clinical symptoms as they cycle into and out of phase, resulting in disrupted nighttime sleep patterns and/or excessive daytime sleepiness.

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A condition that involves involuntary, rapid, repetitive movements of one or both eyes from side to side, up and down, or in a circular motion. Nystagmus may be present at birth or, less commonly, may result from disease or injury. In some cases, the condition can reduce or interfere with vision. For example, children with nystagmus may frequently lose their place when reading. Placing a cutout reading window over words or using a card to “underline” text can be helpful.

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Optic nerve atrophy

Degeneration of the optic nerve, which carries visual information from the eye to the brain. People with optic nerve atrophy may have dimmed or blurred vision and a reduced field of vision. They may also have difficulty seeing contrast and fine detail. Vision loss through optic nerve atrophy is permanent. However, further vision loss may be prevented if the underlying cause can be identified and successfully treated. Bright lighting, high contrast, and bold colors can help children with optic nerve atrophy see more clearly.

Optic nerve hypoplasia

Condition, present at birth, in which the optic nerve is underdeveloped so that adequate visual information is not carried from the eye to the brain. The effects of optic nerve hypoplasia have a broad range, from little or no visual impairment to near-total blindness. The condition may affect one or both eyes. There is no treatment or cure for optic nerve hypoplasia. However, depending on the degree of vision, a person with this condition may benefit from using devices for low vision.

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The eye’s gradually decreasing ability to focus on nearby objects. Presbyopia is a normal part of aging and affects virtually everyone, usually becoming noticeable after age 40. People with presbyopia typically hold reading materials at arm’s length to bring the words into focus. They may experience headaches or eyestrain while reading, viewing a computer screen, or doing close work. Presbyopia can be corrected with reading glasses, bifocal or variable focus, or contact lenses. Using bright, direct light when reading is also helpful.

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Retinal detachment

Separation of the retina from the underlying supportive tissues. Retinal detachment may result from injury, disease, or other causes. A person with retinal detachment usually does not experience pain, but may see floaters (see floaters and spots) or bright flashes of light, may have blurred vision or may see a shadow or curtain over part of the field of vision. Retinal detachment requires prompt medical attention to prevent permanent vision loss. There are several methods of treatment for retinal detachment, including laser surgery.

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Retinitis pigmentosa

Degeneration of the retina results in decreased night vision, a gradual loss of peripheral vision, and in some cases, loss of central vision. The degeneration progresses over time and can lead to blindness. Retinitis pigmentosa is a rare, inherited disease for which there is no treatment or cure. Some ophthalmologists believe that treatment with high doses of Vitamin A can slow the progression of retinitis pigmentosa and that taking Vitamin E makes it worse. Early diagnosis enables a person with the disease to plan and prepare for its progression. In addition, depending on the degree of vision, electronic magnifiers, night-vision scopes, and other special devices for low vision can provide some benefits for people with the disease.

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Malignant tumor (cancer) of the retina, generally affecting children under the age of 6. Usually hereditary, retinoblastoma may affect one or both eyes. Retinoblastoma has a cure rate of over 90 percent if treated early. Without prompt treatment, cancer can spread to the eye socket, the brain, and elsewhere and can cause death. Depending on the size and location of the tumor, treatment options include laser surgery, cryotherapy (a freezing treatment), radiation, and chemotherapy. In some cases, the affected eye may need to be removed.

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Retinopathy of prematurity (ROP)

A condition associated with premature birth, in which the growth of normal blood vessels in the retina stops, and abnormal blood vessels develop. As a result, the infant has an increased risk of detachment of the retina (see retinal detachment). Retinopathy of prematurity can lead to reduced vision or blindness. Laser therapy can help this condition if diagnosis and treatment occur early. Children who experience minor effects may benefit from using devices for low vision as they age. Retinopathy of prematurity was formerly called retrolental fibroplasia.

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Retinopathy of Prematurity

Retrolental fibroplasia

See retinopathy of prematurity.

Rod-cone dystrophy

See Cone-rod dystrophy.

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Gap or blind spot in the field of vision that may result from damage to the retina. How much a scotoma impairs sight depends on whether it affects central or peripheral vision. Common causes of scotoma include macular degeneration, glaucoma, and optic nerve inflammation. People who experience significant low vision because of scotomas may benefit from using magnifiers, bright lighting, and large-print reading materials.

Suggested resource: Scotoma (Blind Spot in Vision): Types, Causes & Treatment (

Septo-Optic Dysplasia (SOD)

See De Morsier’s Syndrome.

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Stargardt’s Disease

An inherited disease that causes gradual degeneration of the macula, the area in the middle of the retina that makes possible the central vision needed for reading, driving, recognizing colors, and other activities of daily life. Effects of Stargardt’s Disease, which start at an early age, vary from minor to total loss of detailed vision. Over years, people with the disease typically lose the sharpness of vision, experience decreased color vision, and may have blind spots. However, peripheral and night vision usually remains unaffected, and complete loss of sight is rare. Stargardt’s Disease has no cure or treatment, but such devices as magnifying screens and binocular lenses can help people cope with vision limitations.

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Condition in which the eyes are not directed simultaneously toward the same point. Strabismus occurs when eye muscles are not working together properly. It is most commonly an inherited condition, but may also be caused by disease or injury. If diagnosed early, strabismus can usually be corrected. The condition may be treated with corrective eyeglasses, eye-muscle exercises, surgery, or a combination of these approaches. Young children with this condition may need to wear an eye patch over their stronger eyes to force their weaker eyes to function correctly. Children whose strabismus is not corrected may develop amblyopia.

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Sturge-Weber Syndrome

The disorder, present at birth, is characterized by a facial birthmark and various neurological, visual, and developmental symptoms. For example, people with Sturge-Weber syndrome may experience seizures, glaucoma, partial paralysis, and learning disabilities. There is no cure for Sturge-Weber syndrome, but many of the symptoms can be treated. For instance, medications may be prescribed to control seizures, and surgery or eye drops may be used to treat glaucoma.

Suggested resource:

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Contagious eye infection, caused by bacteria, affects the eyelid and cornea. Trachoma can lead to scarring and blindness if not treated. The infection is spread by contact with discharge from the eyes or nose of infected persons and transmitted by certain flies. Trachoma is rare in the United States, but it affects millions of people worldwide, many of them children. Antibiotics are generally an effective treatment for trachoma, especially if used early in the infection. In some instances, eyelid surgery may be needed.

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Usher Syndrome

An inherited condition that causes partial or total hearing loss accompanied by gradual vision loss resulting from retinitis pigmentosa. Some people with Usher Syndrome also have problems with balance. There is no cure for the condition. However, early diagnosis makes it possible to help people with Usher Syndrome by providing hearing aids, training in sign language and lip reading, devices for low vision, and counseling for preparing for the future.

Suggested resource:
Usher Syndrome | National Eye Institute (


Inflammation inside the eye affects the structures that provide most of the blood supply to the retina. Uveitis may affect one or both eyes. The condition may be associated with an underlying disease or have other causes, but in many cases, it affects people who are otherwise healthy. People with uveitis typically experience redness of the eye, blurred vision, and light sensitivity. They may also feel pain and see floaters (see floaters and spots). If not properly treated, uveitis can lead to scarring and vision loss. Treatment depends on which eye structures are affected and whether there is an underlying disease. Eye drops and other medications are commonly prescribed to reduce inflammation.

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Vitelliform Macular Dystrophy

See Best’s Disease.

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Loss of vision in the patient from ophthalmologic abnormalities in the eye exam It could be cataract, glaucoma, macular degeneration.

Acute Zonal Occult Outer Retinopathy (AZOOR)

What Causes AZOOR? The cause of AZOOR is unknown, although it is thought to be related to an auto-immune process whereby the individual’s immune system damages the outer or peripheral […]

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retina with spots

Albinism and Low Vision

What Is Albinism? Albinism represents a group of conditions characterized by a defect in the production of the pigment melanin, normally found in skin, eyes, and hair. Any one of […]

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A little boy with an occluder undergoes a hardware vision treatment.


Amblyopia is a reduction in best-corrected visual acuity that cannot be accounted for by any structural abnormality, either in the eye or in the visual pathways (i.e., a pathway or […]

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By Mrinali Patel Gupta, M.D. Aniridia and the Iris The term aniridia is Greek for “without iris.” It is a congenital, bilateral (both eyes) condition characterized by the complete or […]

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Charles Bonnet Syndrome: Why Am I Having Visual Hallucinations?

Many vision professionals believe that a significant number of adults with various eye conditions, including macular degeneration, diabetic retinopathy, and glaucoma, experience Charles Bonnet (“Bo-NAY”) Syndrome, a condition that causes […]

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Close-up of a bloodshot eye


What Is Conjunctivitis? Conjunctivitis is inflammation of the conjunctiva, which is the thin translucent tissue that lines the inner surface of the eyelid and the outer surface of the sclera, […]

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Person putting eye drops into their eye

Dry Eyes

What Is Dry Eye? Dry eye is a condition in which the tears do not sufficiently hydrate the cornea. The cornea is a transparent dome-shaped tissue that forms the front […]

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retina with small tear (text: retinal tear)

Floaters, Retinal Tears, and Retinal Detachments

By Mrinali Patel Gupta, M.D. What Are Floaters? As their name implies, floaters are usually small, black shapes that look like spots, squiggles, or threads and “float about” in one’s […]

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Corneal topography also known as photokeratoscopy for mapping the cornea and diagnosing keratoconus


What Is Keratoconus? Keratoconus is a bilateral (both eyes) degenerative condition of the cornea, a transparent dome-shaped tissue that forms the front part of the eye. Keratoconus gradually causes the […]

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Person selecting eyeglasses

Refractive Error and Astigmatism

The power of your eye to focus and see an image is dependent on several structures within the eye: Myopia or Near-Sightedness People with myopia, or near-sightedness, can see close-up […]

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Premature newborn baby in the hospital incubator. Neonatal intensive care unit

Retinopathy of Prematurity (ROP)

What Is Retinopathy of Prematurity? Retinopathy of prematurity (ROP) is a retina disease that can occur in premature babies. The retina is the thin, light-sensitive tissue that lines the inside […]

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Hemianopsia, or hemianopia, is a less vision or blindness (anopsia) in half the visual field, usually on one side of the vertical midline.


What Is a Stroke? A stroke is an episode of decreased blood flow to the brain’s tissues. This decreased blood flow can be caused by a blockage in a blood […]

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