Visual defects are one of the most common causes of disability. In Britain nearly one million people are blind or partially sighted.
Very few blind people can see nothing at all. Many different eye defects and diseases give rise to visual impairment. In Britain the most common conditions are cataracts, glaucoma, macular degeneration and diabetic retinopathy.
Macular degeneration results in a loss of central vision, but never effects vision at the outer edges of the eye. It does not lead to total blindness, but people with macular degeneration may experience difficulties such as reading mail or recognising faces.
Age related macular degeneration occurs when the delicate cells of the macular become damaged and stop working, usually affecting both eyes. Macular dystrophy, an inherited form of macular degeneration, can affect children and young people.
Treatment: Laser treatment can help some people if the condition is diagnosed early enough. However, this is still experimental and can damage the retina. A variety of optical aids can help in some cases, by using unaffected parts of the retina.
Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged by raised pressure within the eye. Nerve damage can also occur due to reduced blood flow within the optic nerve. Glaucoma can result in two different defects, either defects in the overall field of vision or to central or 'straight ahead' vision.
The eye lens and other tissues are nourished by a fluid called aqueus humour, which circulates around the eye. 'Normal' eye pressure is when the amount of fluid produced balances the amount that is drained away through the eye's outflow channels. If the fluid cannot escape, or too much is produced then pressure rises.
Treatment: Glaucoma can be controlled but not cured. Treatment is usually by eye drops, sometimes by laser and occasionally by an operation to improve the drainage from the eye.
Diabetic retinopathy is the name given to changes in the retina which occur over a period of time. The walls of the blood vessels which feed the retina become fragile and then start to break, leaking blood around them.
Diabetic retinopathy is the most serious diabetic eye condition and is caused by the diabetes mellitus or 'sugar' diabetes. Having diabetes does not necessarily mean that sight will be affected, but there is a higher risk.
Treatment: Most sight threatening diabetic problems can be prevented by laster treatments, if diagnosed early.
Often the first symptom of retinitis pigmentosa is night blindness, followed by a narrowing field of vision leading to what is called tunnel vision. In some cases vision fades between the centre and the edge of the retina and this fading area gradually grows larger until little or no vision remains.
Retinitis pigmentosa is the name given to a group of hereditary diseases of the retina.The retina slowly degenerates and loses its ability to transmit pictures to the brain. Characteristic clumps of pigment usually appear on the retina: hence the term 'retinitis pigmentosa'.
Treatment: There is at present no known treatment that can stop the progress of retinitis pigmentosa.
A cataract is a cloudiness or mistiness in the lens of the eye. In the early stages the visual problems are hardly noticeable. Later, the cataract may be visible through the pupil as a whitish area inside the lens. It can lead to overall loss of vision.
The clouding of a cataract can appear in old age, after an injury or inflammation, or may be congenital. It may also be linked with diabetes. A cataract is not skin growing over the eye, but a change in the nature of the lens itself. The clear jelly like material in the lens turns cloudy which causes the distorted or misty sight.
Treatment: There are several modern methods for the treatment of cataracts. The most effective is to remove the cloudy lens and replace it with a plastic lens implant.
Nystagmyus refers to the rythmical oscillation of one or both eyes. It is an involuntary movement and may be so slight in children as to be barely noticeable, or it can be rapid with a wide range of movement. Central vision is usually reduced due to the failure to provide a stable image on the retina.
Nystagmyus is rare on its own and is often associated with other eye conditions.
Treatment: There is no cure yet known for Nystagmus and few cases can be assisted by any sort of treatment.
The brain is divided into two halves, each with its own blood supply. Each half is responsible for the sensation and movement of the opposite half of the body and it also services the vision for the opposite side. A stroke can cause a loss of vision in both eyes (Hemianopia). When the loss is over a large part of the field of vision, people and objects may be missed, making day to day tasks such as reading and getting about difficult.
Treatment: There is no known medical treatment for strokes. Recovery depends on the concentration of the patient (which can be affected by the stroke) and determination to improve.
Introduction | Artists Albert Dickman, Alan Price & Frank Hengler | Artists Nora Westwood, Ray Corrin, Eileen Stead & Owen Owen | Information on visual problems | National Museums Liverpool