Eye Conditions.

The following documents contain information on various eye conditions

Cataracts

A cataract is a clouding of the normally clear lens of the eye. It may vary in its severity from a small amount of

clouding to dense areas of haziness. A cataract is usually an age-related condition, which disturbs the passage

of light and prevents the eye from focussing correctly. The lens is situated behind the iris (the coloured part of

the eye). Its purpose is to bend light rays so that they provide a clear image to the retina at the back of the eye.

A cataract is caused by metabolic changes within the lens. These changes are very common with age.

Cataracts may also occasionally be caused by injury, radiation, medication or other eye diseases.

Macular Degeneration

Macular Degeneration (MD) is damage or breakdown of the macula. The macula is the part of the retina which

allows us to see clearly and appreciate colour. It is the small spot (approximately 3mm) near the middle of the

retina, which is responsible for the central part of what we see.  The retina is at the back of the eye. It is made up

of cells which are sensitive to light.

Glaucoma

Glaucoma is the leading cause of preventable blindness in the UK, reasonable for 13% of those on the blind

register. It is estimated that about half a million people suffer from glaucoma in the UK alone; about half of these

have the chronic form of the disease and in this group half remain undetected. If it is diagnosed early blindness

is often preventable. The eye is normally filled with 'intra ocular' fluid which constantly drains away and is then

replaced. In the case of glaucoma, intra ocular fluid is not drained away properly, or it may be produced in large

amounts. If this causes too much pressure in the eye, the optic nerve is damaged, blind areas in the field of

vision develop. Glaucoma tends to happen slowly, often with no noticeable changes until after the damage is

done.

Diabetic Retinopathy

This is caused by diabetes, although having diabetes does not necessarily lead to sight loss. Retinopathy

affects the retina. The retina is at the back of the eye and is made up of cells which are sensitive to light.  

Early diabetic retinopathy is sometimes the first indication of diabetes. If your optometrist sees changes to the

retinal blood vessels during your eye examination, they may advise further checks with you doctor. A network

of blood vessels feeds the retina. Diabetes can cause blood vessels to break and this can interfere with vision.

Blood clots and scars may form on the retina, blocking the light rays from nerve cells and interfering with their

nutrition.  Complete loss of vision can occur when scar tissue develops at the back of the eye. This sometimes

pulls and detaches the retina.

Dry Eyes

The eye ball is protected by a layer of tears which have antibacterial properties and keep the eyes moisterised

and comfortable. In addition the tear layer provides a smooth surface for the refraction of the light as it enters the

eye. Dry eye occurs when some of the tear components aren't produced in sufficient quantity. This can cause

grittiness and irritation and also some blurring of vision - particularly is associated with computer use.

Paradoxically the eye may respond by producing extra tears - but these are often of reduced quality so the eye

still feels uncomfortable.

Retinitis Pigmentosa

Retinitis Pigmentosa (RP) is a degenerative, inherited eye condition which affects the retina, resulting in

progressive vision loss. Several layers of cells form the retina. These include rod and cone cells. Their function is

to receive and turn light into electrical impulses which pass along the optic nerve to the brain, enabling sight to

occur.