Eye Conditions

This page summarises various conditions that can cause sight loss. Each summary contains a link for more detailed information and help where available.

Use the A to Z below to link down the page.

A . B . C . D . E . F . G . H . I . J . K . L M . N

O . P . Q . R . S . T . U . V . W . X . Y . Z


Age-Related Macular Degeneration (AMD)

Macular degeneration is a medical condition usually of older adults which results in a loss of vision in the center of the visual field (the macula) because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness in the elderly . Macular degeneration can make it difficult or impossible to read or recognise faces, although enough peripheral vision remains to allow other activities of daily life.

Further reading:

Macular Disease Society

RNIB information on Age Related Macular Degeneration

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Aniridia is a rare congenital condition characterised by the underdevelopment of the eye's iris. This usually occurs in both eyes. It is associated with poor development of the retina at the back of the eye preventing normal vision development. Aniridia does not always cause lack of vision, but usually leads to a number of complications with the eye.

Further reading:

Aniridia Network UK

RNIB information on Aniridia

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Best’s Disease

Best's disease, also known as Best's Vitelliform Macular Dystrophy, is an hereditary form of Progressive Macular Dystrophy.

It is a genetic eye disorder that can cause progressive vision loss. This disorder affects the retina, specifically cells in a small area near the center of the retina called the macula. The macula is responsible for sharp central vision, which is needed for detailed tasks such as reading, driving, and recognising faces.

Further reading:

Macular Disease Society

RNIB information on Best's Disease

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A cataract is a clouding that develops in the lens of the eye, varying in degree from slight to complete opacity and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness (myopia), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours.

Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated. The condition usually affects both the eyes, but almost always one eye is affected earlier than the other.

Further reading:

See also Congenital Cataracts

RNIB information on cataracts

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Charles Bonnet Syndrome

Charles Bonnet Syndrome (or CBS for short) is a term used to describe the situation when people with sight problems start to see things which they know aren't real. Sometimes called 'visual hallucinations', the things people see can take all kinds of forms from simple patterns of straight lines to detailed pictures of people or buildings.

First described by Charles Bonnet in 1769, the syndrome affects people with serious sight loss and usually only people who have lost their sight later in life but can affect people of any age, usually appearing after a period of worsening sight. The visual hallucinations often stop within a year to eighteen months.

Further reading:

RNIB information on Charles Bonnet Syndrome

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Coat’s Disease

Coats’ Disease, also known as Exudative Retinitis, is a progressive condition of the retinal capillaries which occurs in children and young adults, usually males. Commencing typically during the first decade of life, it is gradual in progress and affects central vision, usually in only one eye.

Further reading:

Coats Disease website

RNIB information on Coats Disease

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A coloboma is a gap in part of the structures of the eye. This gap can be large or small and is normally in the bottom part of the eye. A coloboma is caused when a baby’s eyes do not develop properly during pregnancy. This condition occurs in about 1 in 10,000 births.

Coloboma can affect one eye (unilateral) or both eyes (bilateral). Coloboma can affect a number of different parts of the eye. A coloboma does not mean that there is a hole in the eye, but that certain structures or parts within the eye did not fully form.

Further reading:

RNIB information on Colobama

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Congenital Cataracts

A cataract is a clouding of the normally clear and transparent lens inside the eye. It can cause blurry or hazy vision and be a bit like trying to look through frosted glass. It is not a layer of skin that grows over the eye or eyes.

A cataract is called congenital when it is present at birth. It is also known as 'infantile cataract' if it develops in the first 6 months after birth. It can affect one eye, which is known as 'unilateral cataract' or both eyes, which is known as 'bilateral cataracts'. Most children with cataract in only one eye usually have good vision in the other.

Congenital cataracts can continue to develop, although this normally takes months to years. The ophthalmologist (eye doctor) will take all this into account when considering treatment.

Further reading:

See also Cataracts

RNIB information on Congenital Cataracts

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Corneal Dystrophies

Corneal dystrophies are rare conditions in which the cornea is altered without the presence of any inflammation, infection or other eye disease. The clearness (transparency) of the cornea is affected and vision may or may not be disturbed. Corneal dystrophies tend to run in families. They have been described in many different ways but because each dystrophy will start in a particular layer of the cornea, they are classified as epithelial dystrophies, stromal dystrophies or endothelial dystrophies.

Further reading:

RNIB information on Corneal Dystrophies

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Corneal Transplantation

Corneal transplantation, also known as corneal grafting or penetrating keratoplasty, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue which has been removed from a recently deceased individual having no known diseases which might affect the viability of the donated tissue.

The cornea is the clear part of eye in front of the iris and pupil. The surgical procedure is performed by ophthalmologists, medical doctors who specialise in eyes, and are often done on an outpatient basis.

Further reading:

RNIB information on Corneal Transplantation

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Diabetic Retinopathy

Diabetic retinopathy is damage to the retina caused by complications of diabetes mellitus, which can eventually lead to blindness. It can affect a large percentage of patients who have had diabetes for 10 years or more. Despite this, research indicates that at least 90% of these new cases could be reduced if there was proper and vigilant treatment and monitoring of the eyes

Diabetic retinopathy is usually graded according to how severe it is. The three main stages are:

Background Diabetic Retinopathy

This condition is very common in people who have had diabetes for a long time. Your vision will be normal with no threat to your sight.


This is the main cause of loss of vision and may occur gradually but progressively. It is rare for someone with maculopathy to lose all their sight.

Proliferative Diabetic Retinopathy

As the eye condition progresses, it can sometimes cause the blood vessels in the retina to become blocked. If this happens then new blood vessels form in the eye.

Unfortunately, these new blood vessels are weak. They are also in the wrong place – growing on the surface of the retina and into the vitreous gel. As a result, these blood vessels can bleed very easily and cause scar tissue to form in the eye. The scarring pulls and distorts the retina. When the retina is pulled out of position this is called retinal detachment.

- Proliferative retinopathy is rarer than background retinopathy.
- The new blood vessels will rarely affect your vision, but their consequences, such as bleeding or retinal detachment may cause your vision to get worse. Visual loss in this case is often sudden and severe.
- Your eyesight may become blurred and patchy as the bleeding obscures part of your vision.
- Without treatment, total loss of vision may happen in proliferative retinopathy.
- With treatment, sight-threatening diabetic problems can be prevented if caught early enough. However, laser treatment will not restore vision already lost.

Further reading:

NHS information on English National Screening Programme for Diabetic Retinopathy

RNIB information on Diabetes related eye conditions

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Exudative Retinitis

See Coats disease

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Giant Cell (Temporal) Arteritis

Giant Cell Arteritis (sometimes called Temporal Arteritis) is a condition which can seriously affect sight. It is a condition that affects the arteries of the body, in particular the artery that brings blood to the optic nerve. This can cause a lack of blood to the optic nerve which can lead to a sudden loss of vision.

Further reading:

RNIB information on Giant Cell Arteritis

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Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged at the point where it leaves the eye. This nerve carries information from the light sensitive layer in your eye, the retina, to the brain where it is perceived as a picture.

There are four main types of Glaucoma: chronic, acute, secondary and developmental.

Further reading:

RNIB information on Glaucoma

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High Degree Myopia

Myopia is another name for short-sightedness. High degree myopia (sometimes known as pathological myopia or degenerative myopia) is a chronic, degenerative condition which can create problems because of its association with degenerative changes at the back of the eye.

The effects mean that near vision can deteriorate to a level where even very close to the face become hard to focus.

Further reading:

RNIB information on High Degree Myopia

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In keratoconus, meaning “conical or cone-shaped cornea”, the cornea becomes stretched and thins at its centre, and the thinned part of the cornea bulges making the vision more shortsighted and irregular. As a result the vision is distorted. The stretching of the cornea tends to progress but the rate varies. Both eyes are affected but the condition may not be at the same stage in both eyes. The majority of people with keratoconus have no family history of the condition and are very unlikely to have affected children.

Further reading:

UK Keratoconus Self Help and Support Association

RNIB information on Keratoconus (Corneal Dystrophy page)

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See Corneal Transplantation

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Macular Degeneration

See Age-Related Macular Degeneration (AMD)

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Macular Hole

A macular hole is a small hole in the macula which is in the centre of the retina. The macula is the part of the retina which is responsible for our sharp, detailed, central vision. This is the vision we use when we are looking directly at things, when reading, or using a computer.

Macular holes usually only affect one eye, though there is a small chance that the other eye will eventually be affected.

Further reading:

RNIB information on Macular Holes

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Nystagmus is an uncontrolled movement of the eyes, usually from side to side, but sometimes the eyes swing up and down or even in a circular movement. Most people with nystagmus have reduced vision.

Nystagmus that appears in the first months of life is called “early onset nystagmus” or “congenital nystagmus”. The condition may also develop later in life when the term “acquired nystagmus” is used.

Further reading:

Nystagmus.co.uk - Real Life Experiences

RNIB information on Nystagmus

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Posterior Vitreous Detachment (PVD)

Posterior Vitreous Detachment (PVD) is a common condition which occurs in about 75 per cent of people over the age of 65. As people get older the vitreous, a jelly-like substance inside the eye changes. This can cause Posterior Vitreous Detachment.

Symptoms can include flashing lights and floaters, which can take the form of little dots, circles, lines, to clouds or cobwebs. Sometimes people experience one large floater which can be distracting and make things difficult to read.

Further reading:

RNIB information on Posterior Vitreous Detachment

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Retinal Detachment

Retinal detachments often develop in eyes with retinas weakened by a hole or tear. This allows fluid to seep underneath, weakening the attachment so that the retina becomes detached – rather like wallpaper peeling off a damp wall.

When detached, the retina cannot compose a clear picture from the incoming rays of light and vision becomes blurred and dim.

Further reading:

RNIB information on Retinal Detachment

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Retinal Vessel Occlusion

A retinal vessel occlusion is a blockage in the blood vessels of the eye that can cause sight loss. The main cause is Atherosclerosis which is a problem with the condition of the inside of the blood vessel's wall causing patches of sticky blood vessels which are called atherosclerotic plaque.

Problems occur because these sticky patches can catch any debris in the blood which in turn makes the plaques bigger. If the plaques become bigger they can cut off part or all of the blood going to or from the retina. Large pieces of debris can also get caught and block off the blood vessel. This can then cause either a vein or an artery occlusion.

Further reading:

RNIB information on Retinal Vessel Occlusion

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Retinitis Pigmentosa

Retinitis pigmentosa (RP) is the name given to a group of hereditary eye disorders. These disorders affect the retina, which is the light-sensitive tissue lining the back of the eye, in which the first stages of seeing take place. In RP, sight loss is gradual but progressive. It is unusual for people with RP to become totally blind as most retain some useful vision well into old age.

Further reading:

The British Retinitis Pigmentosa Society

RNIB information on Retinitis Pigmentosa

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Retinopathy Of Prematurity

Retinopathy of prematurity (ROP), previously known as Retrolental Fibroplasia (RLF), is an eye disease that affects prematurely born babies. It is thought to be caused by disorganised growth of retinal blood vessels which may result in scarring and retinal detachment.

ROP can be mild and may resolve spontaneously, but 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.

Further reading:

ROPARD - The Association for Retinopathy of Prematurity and Related Diseases

RNIB information on Retinopathy Of Prematurity

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Squints In Childhood (Strabismus)

A squint is a problem when the eyes stop working together as a pair and therefore do not look in the same direction. One eye may turn inwards (most common in children), outwards or even upwards or downwards. Squints are common and may affect up to 5 per cent of all children.

A squint that turns inwards is called a 'convergent squint' or 'esotropia' and one that turns outwards is termed a 'divergent squint' or 'exotropia'.

Further reading:

RNIB information on childhood squints

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Stargardt’s Macular Dystrophy

Stargardt's Macular Dystrophy causes some of the cells on the macula to stop working leading to problems with central vision, detailed vision and sometimes with colour perception.

The macula is found at the centre of the retina where the incoming rays of light are focused. The macula is very important and is responsible for:

- what we see straight in front of us
- the vision needed for detailed activities such as reading and writing, and
- our ability to appreciate colour.

It is sometimes called a Juvenile Macular Dystrophy since it tends to first appear between the ages of 10 to 20.

Further reading:

RNIB information on Stargardt’s Macular Dystrophy

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Stroke Related Eye Conditions

As seeing involves not only the eyes but the brain as well, stroke-related vision problems can be very complex to understand and treat.

Problems can include:

- Field loss (Hemianopia)
- Eye muscle and nerve problems (Diplopia)
- Vision processing problems
- Increased sensitivity to light
- Dry eye

Further reading:

The Stroke Association

RNIB information on Stroke related eye conditions

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Temporal Arteritis

See Giant Cell Arteritis

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Thyroid Eye Disease

Thyroid eye disease (thyroid orbitopathy or TO) is a condition of the soft tissues such as the fat and muscles surrounding the eyes. The condition is characterised by a period of inflammation and engorgement of these tissues, followed by a healing response.

The condition most commonly occurs in association with an overactive thyroid gland, but can also occur with an under active thyroid gland.

Further reading:

RNIB information on Thyroid eye disease

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Uveitis is an inflammation of the uvea. In most cases, the cause is unknown, but infectious or immunological systemic disorders can cause uveitis.

The type of uveitis you have is classified by where inflammation occurs in the uvea:

- Anterior uveitis refers to inflammation of the iris alone (iritis) or the iris and ciliary body.
- Intermediate uveitis refers to inflammation of the ciliary body.
- Posterior uveitis is inflammation of the choroid.
- Diffuse uveitis is inflammation in all areas of the uvea.

Symptoms vary depending on where in the uvea the inflammation occurs; they include mild to strong eye pain, redness, light sensitivity, blurred vision and floaters. You may also experience tearing, a pupil that responds poorly to light or squinting. Specific types of uveitis include, iritis, iridocyclitis, cyclitis, pars planitis and choroiditis.

Further reading:

RNIB information on Uveitis

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Vitelliform Macular Dystrophy

See Best's Disease

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