Information about eye diseases

The macular is the part of the retina that is responsible for central vision and the ability to see detail. Macular degeneration describes a condition in which this retinal tissue of the macular can not function properly. If it occurs later in life it is called age-related macular degeneration (AMD). AMD affects central vision and can vary in its severity. It does not affect peripheral vision.

AMD is diagnosed as either “wet” or “dry”. About 10% of people with macular degeneration have wet AMD. Wet AMD occurs when new blood vessels form to try and improve the blood supply to the retinal tissue. These new blood vessels can break and cause bleeding to surrounding tissue which can scar the retina. Dry AMD is more common and generally results in a slower loss of vision. It is characterised by small deposits called “drusen” forming in the retina.

There are many factors thought to be possible causes for macular degeneration. These are linked to age, gender, genetics, nutrition and exposure to smoking and sunlight

Amblyopia is the term used when vision in one eye is reduced because the eye and the brain are not working together properly. When light enters the eye it is changed into nerve signals. These travel to the brain along the optic nerve. Although the eye affected may look normal, it is not being used normally because the brain is favouring the other eye. This is why the condition is also sometimes called “lazy eye”.

Amblyopia can be caused by strabismus, when one eye is misaligned with the other when focusing, by anisometropia, where there is different vision in each eye and/or by a blockage of an eye due to trauma.

Aniridia is a rare genetic eye condition that is present at birth. It is characterised by the incomplete formation of the iris, usually in both eyes, and is associated with poor retinal function. This is because the muscles that open and close the pupil are missing and as such the appearance of a black iris is the result of a very large pupil. Aniridia is caused by a genetic abnormality of the PAX6 gene.

Behçet’s disease is a chronic condition involving inflammation of arteries and veins throughout the body. Inflammation of the eye (uveitis, retinitis, and iritis) occurs in more that half of those with Behçet's disease and can cause blurred vision, pain and redness.

The severity of the disease varies from patient to patient. Some patients may live normal lives, but others may become blind or severely disabled. There is no cure for Behçet's disease and treatment typically focuses on reducing discomfort and preventing serious complications. Corticosteroids and other medications that suppress the immune system may be prescribed to treat inflammation.

A cataract is the clouding of the lens and results in blurred vision. The lens comprises mostly water and protein and the protein normally allows the lens to remain clear and let light pass through. The protein may aggregate, however, and start to cloud a small area of the lens. This is a cataract.

Cataracts are most common in people over the age of 60 although some babies are born with cataracts or they may develop in childhood. Cataracts can also develop as a result of an injury to the eye or after exposure to some types of radiation.

Choroideremia is a rare inherited disorder that causes progressive loss of vision due to the degeneration of the choroid and of layers of the retina including the retinal pigment epithelium (RPE) and photoreceptors. The choroid provides the RPE and the photoreceptors with nourishment, including oxygen. When the choroid and the RPE degenerate this prevents the photoreceptors from fulfilling their function of capturing light rays and converting them to electrical impulses to be transmitted to the brain.

Choroideremia is genetically passed through families by the X-linked pattern of inheritance. As such, the condition is evidenced almost exclusively in males.

The The Tommy Salisbury Choroideremia Committee is dedicated to raising funds for research into choroideremia.

The transparency of the cornea is vital for vision. Due to its exposed position it is vulnerable to infection and can be invaded by viruses, bacteria and fungi. A corneal ulceration occurs when the cornea is damaged.

Ulcers may be sterile or infectious. Bacterial ulcers are infected and are generally painful and associated with a break or tear in the epithelium layer of the cornea. Certain types of bacteria can be very aggressive and cause blindness within a matter of days if left untreated. Sterile ulcers may not cause pain and may not be accompanied by a break in the epithelium of the cornea.

There are many causes of corneal ulcers which are common in humans. These include trauma, chemical injury, contact lenses and infections. Other eye conditions can also cause corneal ulceration.

Diabetes occurs as a result of a lack of insulin or where the body is unable to process insulin properly. Insulin acts as a regulator of blood sugar levels. Diabetes may have an impact on the eyes in several ways, the most important being the effect that it has on the retina and the blood vessels within the retina. This is known as diabetic retinopathy.

In the early stages of diabetic retinopathy the blood vessels of the retina weaken and can break leading to bleeding and potential scarring in the retina which can reduce vision. In order to try to deliver nourishment and oxygen to the retina new blood vessels develop. These can also break easily. As the disease progresses new blood vessels may continue to grow and break with blood leaking in the retina and the vitreous gel. Scar tissue may develop on the retina. The affect of diabetic retinopathy on sight can vary widely depending on the stage of the disease. In the later stages of the disease this new blood vessel growth and scarring could lead to other eye conditions including retinal detachment and glaucoma.

Duane syndrome is a congenital eye movement disorder in which there is a miswiring of the eye muscles. This causes some eye muscles to contract when they should expand and vice versa. People with the syndrome have limited, and sometimes no, ability to move the eye outwards towards the ear and, in most cases, limited ability to move the eye inwards toward the nose. Often, when the eye moves toward the nose, the eyeball also pulls into the socket (retracts), the eye opening narrows and, in some cases, the eye moves upward or downward. Many patients with Duane syndrome turn their face to maintain binocular vision and compensate for improper turning of the eyes. In 20% of cases, both eyes are affected.

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.

The eye needs a certain amount of pressure to keep the eyeball in shape so that it can work properly. In some people, the glaucoma damage is caused by raised eye pressure. Others may have an eye pressure within normal limits but damage occurs because there is a weakness in the optic nerve. In most cases, both factors of high pressure and weakness in the optic nerve are involved, but to a varying extent.’

In a normal eye the cells behind the iris produce a fluid called aqueous. This is normally kept in balance by the fluid passing through the pupil and leaving the eye by drainage channels to the blood stream between the iris and the cornea. If the fluid can not leave the eye or too much is produced then eye pressure will rise. If left untreated the increase in pressure can damage the optic nerve and the retina and lead to irreversible blindness. Early detection and treatment can slow or even halt the progression of the disease.

Open angle (or “chronic”) glaucoma is the most common type. This is where the drainage channels become blocked over many years and vision deteriorates slowly.

Acute angle glaucoma occurs because the structure of the eye is such that the space between the iris and the cornea is more limited and therefore it is difficult for the aqueous to drain away. If the flow becomes completely blocked then pressure could rise very quickly.

Other types of glaucoma include secondary glaucoma where a rise in eye pressure is caused by another eye condition and a rare condition in babies called congenital glaucoma.

Certain factors may increase the risk of glaucoma. These include age, race and whether other family members have glaucoma.

Keratoconus is a degenerative disease of the cornea. It causes the cornea to gradually thin and change in shape so that it protrudes from the eye in a cone-like shape. This then impacts on the ability of the cornea to help focus light on the macula and vision can become blurred and distorted. It usually affects both eyes. It can be inherited. 

Leber’s congenital amaurosis (LCA) is a group of severe inherited retinal diseases.  (can be developmental, dysfunction and/or degenerative). These diseases are characterised by severe loss of vision from birth and by nystagmus and sluggish or no pupillary responses.

LCA is most typically passed through families by the autosomal recessive pattern of inheritance. Both parents, called carriers, have one faulty gene for the disease paired with one normal gene. Each of their children has a 1 in 4 chance of inheriting the two LCA genes (one from each parent) needed to cause the disorder. Carriers are unaffected because they have only one copy of the faulty gene.

The macular is the part of the retina that is responsible for central vision and the ability to see detail. Macular degeneration describes a condition in which this retinal tissue of the macular is deprived of nourishment and oxygen and the cells can not function properly. If it occurs later in life it is called age-related macular degeneration (see above). Other types of macular degeneration affect children and young adults. These different forms are known as juvenile macular degeneration, early-onset macular degeneration or macular dystrophy.

The different types of juvenile macular degeneration are caused by genetic mutations that affect the macular cells.
The commonest form is Stargardt's disease which is inherited in an autosomal recessive pattern. This means that a child has a one in four chance of inheriting the relevant gene if it is carried by both parents.

The second most common form of juvenile macular degeneration is Best's vitelliform retinal dystrophy. It is inherited in an autosomal dominant pattern and a child has a one in two chance of inheriting the relevant gene.

Nance-Horan syndrome, also referred to as Cataract Dental Syndrome is a rare condition present at birth. It is characterised by cataract as well as abnormal development of the teeth. In many cases children affected may have developmental problems.

The syndrome is inherited by an X-linked recessive pattern which means that it is more severe in males. Carrier females usually develop the cataract however the symptoms are usually less severe.

Nystagmus is an involuntary movement of the eyes, usually from side to side in one or both eyes. There are a number of different causes of nystagmus and it can be present at birth (Congenital Nystagmus) or appear later in life (Acquired Nystagmus) as a result of disease or injury. Most individuals with nystagmus experience reduced vision although the severity may differ in different people. It is rarely a blinding condition.

The optic nerve is responsible for transmitting visual information from the retina to the brain. If the optic nerve is diseased or severely damaged vision loss or blindness can occur. Optic nerve disease can result as a consequence of a variety of other conditions including glaucoma, inflammatory conditions and hereditary conditions such as Leber’s Hereditary Optic Neuropathy. 

The retina is responsible for converting light rays into electrical impulses that are then transmitted to the brain. If the retina becomes detached then it is not able to correctly compose a picture and so vision becomes blurred and dimmed. It is also possible for the retina to tear and this can lead to retinal detachment.

There are three main types of retinal detachment. The most common is when a tear or break in the retina allows fluid to get under the retina and separate it from the retinal pigment epithelium (RPE), the pigmented cell layer that nourishes the retina. The second type, which is less common, is when scar tissue on the retina's surface contracts and causes the retina to separate from the RPE.

The third type is when fluid leaks into the area under the retina without there being any breaks in the retina. These are frequently caused by retinal diseases, including inflammatory disorders and injury/trauma to the eye.
A retinal detachment can occur at any age, but it is more common in people over the age of 40.

When a baby is born prematurely the blood vessels of the retina may not have been fully developed. As a result the vessels may develop abnormally after birth and this may impact on the delivery of oxygen and nourishment to the retina. In addition these new blood vessels may go on to cause bleeding and scarring which can cause vision loss and in the most severe cases, irreversible blindness. 

Retinitis pigmentosa (RP) is the name given to a group of inherited disorders of the retina, all of which result in a progressive reduction in vision. This is as a result of a degeneration of rod, followed by cone photoreceptors in the retina. The rod cells are responsible for peripheral and vision in dim light, but once cone cells are affected daylight, detailed vision can be affected. The severity of the impact of RP differs widely.

The disease may follow different inherited patterns including X-linked (affecting males), autosomal recessive and autsomal dominant traits. 

Strabismus (or cross-eyed) is a condition in which a person can not align both eyes simultaneously under normal conditions. One or both eyes may turn in, out, up or down. The turn may be constant or intermittent. Normally, each eye will focus on the same spot and similar but slightly different messages will be sent back to the brain which merges the two images into one. As a result of strabismus one clear image is not possible and in some cases double vision results. There are many causes of strabismus. It may be present at birth or acquired later as a result of trauma, disease or surgery.

Uveal melanoma is the most common type of cancer originating in the eye. It involves the iris, ciliary body or choroid with advanced tumours affecting at least one of these structures. Tumours arise from the pigment cells that give colour to the eyes. Symptoms include blurred vision, flashing lights, shadows and cataracts.

Together the iris, ciliary body and choroid are known as the uvea. Uveitis is a general term that relates to the inflammation or swelling of any of these structures. The most common type is known as anterior uveitis which involves the iris and the ciliary body. Uveitis can be caused by an infection, a parasite or by trauma. Depending on the type of uveitis, symptoms range from light sensitivity and blurred vision to a rise a eye pressure and pain.