CAUSES OF BLINDNESS
In the UK the most common causes of blindness are age-related macular degeneration (AMD), glaucoma and from the effects of diabetes. Cataract used to be included in the list but with modern surgery people in Britain are rarely allowed to go blind. Globally there are 39 million who are blind according to the World health Organization (WHO) figures and 246 million who have moderate to severe visual impairment. (314 million in 2004.) The most common causes of blindness throughout the world, if uncorrected vision is excluded, are cataract, glaucoma and AMD. Diseases such as trachoma (3%) and onchocerciasis (0.7%) are in decline.
Cataracts occur when the lens in the eye becomes cloudy. The cloudiness reduces vision and can sometimes cause double vision and glare. Cataracts can be detected during a routine eye examination and in many early cases a change of spectacle prescription is all that is required. However, an operation can be performed if spectacles can no longer improve vision to an adequate standard. It is estimated that there are 2.8 million cataract sufferers in the UK with a total cost of around £11bn in 2003.
AGE-RELATED MACULAR DEGENERATION
Age-related macular degeneration, often referred to by its abbreviated form AMD or ARMD, is a degenerative condition affecting the macula region at the back of the eye causing loss of central detailed vision. There are two types of AMD, dry and wet; dry AMD results from a disruption to the blood circulating at the back of the eye causing tissue damage, whereas wet AMD results from a leakage to nearby blood vessels. AMD may be detected by examining the eye using a type of optical torch called an ophthalmoscope or with special lenses and a slit-lamp bio-microscope. It may be treatable by laser photo-coagulation or more recently injections such as lucentis, in about 10% of cases of the wet type of AMD, but if poor vision remains the patient may require the use of a low vision aid. Elderly Europeans are most at risk from AMD.
Diabetes can affect the eyes in a number of ways but chiefly by the growth of new weak blood vessels which can burst at the back of the eye. The problem may be detected by examining the eye using special microscopes. In some cases laser treatment can be given to prevent the condition deteriorating. Approximately one in 10 diabetics will have some sort of retinal disease requiring assessment and/or treatment.
At present there approximately one and a half million diabetic patients that are known to the medical establishment and a further one million people in this country who are unaware they have the condition. Patients from South Asia including India, Pakistan and Bangladesh are most at risk from diabetes.
is usually caused by too much pressure in the eye. But, as the condition is painless and affects only side vision in the early stages, a person may be unaware that the disease is present. If left untreated tunnel vision and eventual blindness can result. Fortunately, the majority of cases are treatable using eye drops. Black African, Afro-Caribbean and East Asian people are most at risk and all of these adult patients should have the pressure of their eyes measured routinely during an eye examination.
It is estimated that glaucoma affects one in 50 people over 40 years of age which is some 2.2 million people in the UK which according to the Guide Dogs for the Blind Association costs the state about £38m annually!
Retinal detachment, as its name suggest, is a condition where part of the retina (the thin film lining the inside of the eye) is pulled away from the back of the eye. If the retina is not put back in place with a day or two it loses its ability to help us see and causes blindness. The most common type of retinal detachment is known as rhegmatogenous retinal detachment and affects 1 in 10, 000 people. It is usually a horseshoe shaped tear in the retina, often from a posterior vitreous detachment where the jelly in the eye is pulled from the retina, and is more likely in short-sighted people. East Asian people, who are more likely to be highly myopic (short-sighted), are more likely to suffer a retinal tear. Treatment consists of sealing the retinal break using a laser. In July 2010 Ann Widdecombe was close to blindness in one eye from a retinal detachment before surgery saved her sight.
EYE DISEASE IN BABIES
Premature babies are prone to a condition known as retinopathy of prematurity which can cause blindness. In Britain 8,000 of the 700,000 babies born every year are at risk of having this condition. If retinopathy of prematurity is present, laser surgery to cause approximately 2,500 burns on the blood vessels at the back of the eye is required, to prevent blindness from retinal detachment.
SEASONAL ALLERGIC CONJUNCTIVITIS
In most cases both eyes are affected by itching, burning, sensitivity to light, redness and watering. Some people inherit a disposition to allergies which may be caused by pollen (hay fever), grass, tree, house dust mites, animal hair and mould. Patients are advised to avoid trigger factors, wash hair and clothes regularly, keep windows closed at night, and choose holidays near mountains or seaside.
Retinitis pigmentosa is a dystrophy (deterioration) of the receptors of the back of the eye affecting the rods first and later on the cones as well. It is usually hereditary and may be linked with a number of syndromes (conditions affecting other parts of the body), such as Laurence-Moon and Bardet-Biedl syndrome, Usher's syndrome, Bassen-Kornzwieg syndrome and Kearns-Sayer syndrome.
ASPECTS OF VISION LOSS
The definition of blindness has for many years been described as being "so blind as to be unable to do any work for which eyesight is essential". This definition is obviously open to interpretation but blindness is usually taken to mean that a person is unable to read the largest letter of the optician's letter chart from a distance of three metres. Government figures indicate that around 157,000 people in the UK are registered as blind and 155,000 partially sighted. Figures collected by the Guide Dogs for the Blind Association in 2003 estimate that there are some 920,000 people with blindness or visual impairment in England alone. The Royal College of Ophthalmologists estimate that in the UK in 2003 approximately 4.3 million people over 65 had visual impairment in one or both eyes. The most common causes for patients becoming blind are age-related macular degeneration, cataracts, glaucoma and diabetes. Information on these diseases is available on this website with pages devoted to age-related macular degeneration, cataracts and glaucoma.
Surgical treatment for eye diseases is available but with variable success. These days a cataract operation is 99% successful and the results achieved are improving all the time as techniques are refined. Incidentally a laser is not used in a cataract operation. Operations for age-related macular degeneration is rarely successful although there are some newer techniques on the way. Eye drops are the usual treatment for glaucoma with an operation being advisable in a small number of cases. Diabetics can grow extra blood vessels at the back of the eye which can break easily and affect the sight. The new vessek can be sealed off using a laser.
PREVENTION OF EYE DISEASE
Over recent years there have been many reports of vitamins and other substances, such as omega 3 oils and various minerals, being of benefit to the preservation of good sight. Most of the anecdotal stories may be dismissed but there are some scientific studies showing that some foods are able to benefit the health of the eye. What is certain that patients who live in socially deprived areas suffer more eye disease than those in more affluent areas. More information on this subject may be found by clicking on
WHAT CAN BE DONE?
When the specialist at the hospital pronounces someone blind and officially registers them as blind you might think that nothing can be done for them. However, about 70% of registered blind patients have some usable vision and there are many thousands of patients who have benefited greatly from the use of low vision aids. Low vision aids are appliances which can enable patients to maximise the available vision and may consist of simple magnifiers, more complex telescopic aids or even closed circuit televisions. See the low vision page for more information by clicking on
LOW VISION SERVICES.