Glossary of Terms
Common terms, symptoms, tests, treatments, surgery, diseases & conditions that eye doctors use.

Glossary of Terms

Your eyes are remarkable devices that allow you to understand the enviroment around you, but they are also fragile and at risk of infection, damage or any other ocular disorder. This section contains information about the most common eye disorders, diseases and complaints as well as providing details about how to treat the problem if possible. This section is only meant to be a guide so it is important that if you do have a serious eye disorder or complaint you consult your GP for further advice.

Acanthamoeba Keratitis
Contact lens wearers who experience any kind of unusual pain in their eyes should visit their optometrist or contact lens practitioner straight away.
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Adie's Pupil
It is generally associated with loss of some reflexes, such as the knee-jerk. It occurs mainly in middle age, and more commonly in women than in men.
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Age-Related Macular Degeneration
Imagine that your eye is like a camera. There is a lens and an aperture (an opening) at the front, which both adjust to bring objects into focus on the retina at the back of your eye.
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Amblyopia
In essence, amblyopia is a disorder of the brain cells that control the vision in one eye, not a problem with the eye itself. The brain cells diminish in size when they are not used.
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Angioid Streaks and PXE
Angioid streaks are broad, irregular, red to brown to grey lines which radiate from the area around the optic nerve head under the retinas of individuals with pseudoxanthoma elasticum (PXE).
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Anophthalmia and Microphthalmia
The fight for answers goes on - questions are still being asked, 'what caused my child's visual impairment?'
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Astigmatism
The cornea is reshaped to allow light to focus properly on the retina. With refractive surgery, the eye regains its proper focusing ability and astigmatism is corrected.
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Azoor
The condition usually presents with flashing lights and an enlarged blind spot. The area of visual loss may spread for a period and then become stable.
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Blepharitis
Blepharitis has multiple causes but is usually caused by seborrheic dermatitis, a bacterial infection, or a combination of both, allergies, or infestation with lice (in the eyelashes).
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Cataracts
The most effective treatment for cataracts is a small operation to remove the cloudy lens. This cannot be performed by laser, although laser treatment is sometimes needed afterwards.
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Coloboma
Although no specific pattern has been identified there appears to be a strong hereditary factor in the incidence of this condition, which is sometimes linked to chromosomal disorders.
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Colour Vision Deficiency
The nerve cells which receive and process light at the back of the eye - the retina - are of two main types: the rod-like cells, which operate at night and the cone-like, which allow us to see fine detail and colours by day.
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Conjunctivitis
Conjunctivitis is an inflammation of the conjunctiva, the thin, transparent layer that lines the inner eyelid and covers the white part of the eye.
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Corneal Dystrophy
The globe of the eye is made of five layers and the cornea is the transparent front portion. It is also the most sensitive structure in the body because of the density of nerves.
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Diabetes and Your Vision
Diabetes mellitus or `sugar diabetes' affects about one person in fifty in the UK. This means that the body cannot cope normally with sugar and other carbohydrates in the diet.
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Diabetic Retinopathy
This condition is very common in people who have had diabetes for a long time. Your doctor may be able to see abnormalities in your eyes, but there is no threat to your sight.
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Disorders of the Conjunctiva
Adults can contract gonococcal conjunctivitis during sexual activity if, for example, infected semen gets into the eye. Usually only one eye is involved.
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Double Vision
Double vision can be extremely discomforting. The brain acts to alleviate the discomfort by suppressing, or blanking out, one of the images.
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Drusen
Small, sharply defined, circular, yellow or white dots lying below the level of the retinal vessels, either discreet or coalesced into larger masses, located throughout the fundus but tending to collect in the region of the macula, around the optic disk, or in the periphery.
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Dry Eye
When we blink, tears form a film which spreads over the eye, making the surface smooth and optically clear and enabling good vision.
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Dyslexia & Vision
Dyslexic children are usually poor at spelling and may seem intelligent in conversation but have trouble with written language. Leonardo da Vinci and Einstein are both thought to have been dyslexic.
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Entropion
This is a condition that commonly affects the lower eyelid, causing it to turn inwards, resulting in the eyelashes rubbing on the front of the eye.
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Episcleritis
Episcleritis presents as a relatively asymptomatic acute onset redness in one or both eyes. Typically, you'll observe a sectoral injection of the episcleral and overlying conjunctival vessels, although the redness may be diffuse throughout these tissues.
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Eyelid and Tear Gland Disorders
The eyelids play a key role in protecting the eyes. They help spread moisture (tears) over the surface of the eyes when they close (for example, while blinking); thus, they help prevent the eyes from becoming dry.
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Farsightedness
If you can see objects at a distance clearly but have trouble focusing well on objects close up, you may be farsighted. Your eye care practitioner may refer to farsightedness as long-sightedness, or by its medical names, hypermetropia or hyperopia.
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Fuchs Dystrophy
Fuchs dystrophy is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. Although doctors can often see early signs of Fuchs dystrophy in people in their 30s and 40s, the disease rarely affects vision until a person reaches their 50s and 60s.
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Glaucoma
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.
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Herpes Simplex Infection
When a corneal herpes simplex infection (herpes simplex keratoconjunctivitis, keratitis) begins, it may resemble a mild bacterial infection because the eyes are slightly painful, watery, red, and sensitive to light.
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Herpes Zoster (Shingles) Eye Infections
Herpes zoster is the medical name for shingles. It is caused by reactivation in the adult years of the chicken pox virus that occurred during childhood (the varicalla-zoster virus).
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Iritis
Iritis is the inflammation of the iris, the coloured portion of the eye. It has been known cause extreme pain, light sensitivity and sight loss, which is often the result of a disease in another part of the body.
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Keratitis
Infection or inflammation of the cornea (the centre portion of the eye that surrounds the pupil).
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Keratoconus
Keratoconus is a vision disorder that occurs when the normally round cornea (the front part of the eye) becomes thin and irregular (cone) shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision.
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Lattice Degeneration
The patient is usually over age 20 and is nearly always asymptomatic, except for possible complaints of flashing lights (photopsia). There appears to be a higher incidence of myopia in patients with lattice degeneration. There is no racial or sexual predilection.
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Macular Hole
The human eye is shaped like a ball, measuring approximately one inch across, and functions like a living camera. The front portion of the eye, consisting of the cornea (the clear cover of the eye), the lens and the iris (the coloured portion of the eye), acts to focus light on the back of the eye, much like the lens and aperture system of a camera focuses light on a piece of film.
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Myopia - Nearsightedness
Your eye care professional may refer to the condition as myopia, a term that comes from a Greek word meaning "closed eyes." Use of the word "myopia" for this condition may have grown out of one of the main indications of nearsightedness: Squinting to see distant objects clearly.
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Myopia - Short Sightedness
Myopia (short-sightedness) occurs when rays of light are brought to a focus in front of the retina because the optical power of the eye is too great, or the eye is too long. The latest research finally proves that contact lenses can slow down the progression of Myopia and, in some cases, halt it all together.
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Nystagmus
Nystagmus is an involuntary movement of the eyes - usually from side to side, but sometimes the eyes oscillate up and down or even in a circular motion. Most people with nystagmus have vision which is much worse than average - well below what is considered to be short sighted.
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Ocular Myasthenia
Much has been written about Myasthenia Gravis (MG) in recent years, because there now seems to be a plausible, scientific explanation for the cause of this disease. The word "gravis" seems no longer appropriate, as current forms of treatment have allowed patients to live fully functional and independent lives.
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Ocular Rosacea
Ocular rosacea is associated with a chronic skin condition known as acne rosacea. The problem usually affects those with light skin, and is characterized by redness and bumps concentrated on the forehead, nose and cheeks.
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Photophobia
Light sensitivity, also called photophobia, is a sensitivity or intolerance to light. Light sensitivity may occur with sunlight, fluorescent light or incandescent light. Sometimes light-sensitive people are bothered only by bright light.
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Posterior Vitreous Detachment
Posterior Vitreous Detachment or PVD for short is a common condition that occurs in about 75% 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.
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Presbyopia
Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects.
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Ptosis
Ptosis (pronounced TOE-sis) is the medical term for drooping eyelids. A person with ptosis is not able to lift one or both upper eyelids to uncover the eye completely.
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Retinal Detachment
Imagine that your eye is like a camera, and the retina is the film. The retina is a fine sheet of nerve tissue lining the inside of the eye (see diagram). Rays of light enter the eye and are focused on the retina by the lens. The retina produces a picture that is sent along the optic nerve for the brain to interpret.
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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.
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Sjögren's Syndrome
Sjögren's Syndrome (SS) pronounced 'show-grins', is one of the most common and least diagnosed rheumatic diseases. In some patients, it presents as only vague symptoms of dry mouth and irritated eyes, while in others it is associated with severe systemic illness and autoimmunity and may even terminate in lymphoid malignancy.
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Solar Retinopathy
The name given to eye damage which has been caused by looking directly at the sun is solar retinopathy. The eclipse of the sun on the 11 of August 1999 put the whole of the country at risk of eye damage due to the temptation for people to stare at the sun.
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Spots, Floaters & Flashes
Spots or floaters are small, semi transparent or cloudy particles within the vitreous, (which is the clear, jelly-like fluid that fills the inside of your eyes). They are quite common and usually, but not always, harmless.
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Squint
Squint can be a complex condition and not every situation is covered in this factsheet, but your practitioner or eye specialist will be pleased to give you further advice, if needed. Your child will benefit from your support and encouragement during treatment, so do not be afraid to ask questions that will help you to understand more easily the condition and treatment.
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Temporal Arteritis
Arteritis is a condition which can cause sudden loss of sight in one eye. Arteritis may be generalised or confined to one area .
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Thyroid Eye Diseases
This is a disorder where the fat and muscles behind and around the eyes become swollen. There is still much that we do not know about it. However it seems to occur only in people who have a certain type of thyroid problem called an auto-immune disorder.
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Uveitis
A big problem, when trying to understand Uveitis, for patients and doctors alike, is that there are many different types of Uveitis.
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vCJD & The Eye
Creutzfeld-Jakob Disease (CJD) is a frightening but nonetheless intriguing disease. It occurs in most populations at approximately 1 case per million per year.
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Vitreous and Retinal Detachment
Most of the serious retinal problems that require surgery are caused by problems with the vitreous, the clear jelly-like substance that fills the space in the eye.
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