Blindness

The term visual impairment refers to someone who is blind or partially sighted. It does not refer to someone who is short-sighted (myopia) or long-sighted (hyperopia).

Facts

Worldwide, about 314 million people are visually impaired. Of these, approximately 14% (45 million) are blind.

Most people (87%) who are visually impaired live in developing countries. In developing countries, cataracts (a cloudy area that forms in the lens of the eye) are responsible for most cases of blindness (48%).

With the right treatment, about 85% of visual impairment cases are avoidable, and approximately 75% of all blindness can be treated or prevented.

Due to improved public health, the number of people who become blind after having an infectious disease has fallen over recent years. However, age-related visual impairment is increasing.

Visual impairment usually affects older people. Globally, women are more at risk than men.

Partial sightedness and blindness

If you are visually impaired, you will have some loss of vision or some distortion to your vision. Depending on the severity of your sight loss or the degree of distortion, the conditions are usually referred to as partial sightedness or blindness.

Partial sightedness

Someone who is partially sighted has a serious loss of sight but they are not blind.

The World Health Organization (WHO) defines partial sightedness as where a person cannot clearly see how many fingers are being held up at a distance of 6m (19 feet) or less, even when they are wearing glasses or contact lenses.

Blindness

WHO defines blindness as severe sight loss, where a person is unable to see clearly how many fingers are being held up at a distance of 3m (9.8 feet) or less, even when they are wearing glasses or contact lenses. However, someone who is blind may still have some degree of vision.

Driving

Visual impairment can have serious implications for driving. If you have a medical condition or disability, such as partial sightedness or blindness, you must inform the RSA.

Sight loss can be sudden and severe, or it can be a gradual deterioration over a long period of time. In most cases, sight loss occurs gradually with distant objects slowly becoming more difficult to distinguish.

As well as a reduction of vision, you may experience other symptoms such as:

  • eye pain
  • a burning or gritty sensation in your eyes
  • a blurring or distortion of your vision

However, symptoms such as these are usually caused by specific eye-related problems, such as:

  • glaucoma (a group of eye conditions that affect your vision)
  • dry eye syndrome (keratoconjunctivitis)
  • cataracts (where a cloudy area forms in the lens of the eye)
  • macular degeneration (where your vision gradually begins to deteriorate over a long period of time)

Glaucoma

Chronic glaucoma

In cases of chronic (long-term) glaucoma, there are not usually any noticeable symptoms because the condition develops so slowly. Your outer field of vision (peripheral vision) is affected first, and then the visual field towards the centre of your eye gradually begins to deteriorate.

As changes to vision are often linked to getting older, it is very important that you have regular eye tests. How often you need to have an eye test will vary depending on your individual circumstances. Ask your optometrist (eye care specialist who carries out eye tests) for advice about this. However, for most people, an eye test at least every two years is recommended.

Acute glaucoma

If you have acute (short-term but severe) glaucoma, you may experience the following symptoms:

  • intense pain in your eye
  • redness of your eye
  • headache
  • sore, tender eye area
  • seeing halos or rainbow-like rings around lights
  • misty vision

Congenital glaucoma

In cases of congenital glaucoma (where the condition is present at birth or develops shortly after birth), the following symptoms may be present:

  • large eyes (due to pressure that causes them to expand)
  • sensitivity to light
  • a cloudy appearance to the eyes
  • watery eyes
  • jerky movements of the eyes
  • a squint (where the eye turns inwards, outwards, upwards or downwards)

Dry eye syndrome

The symptoms of dry eye syndrome can include:

  • feelings of dryness, grittiness or soreness in both your eyes, which gets worse throughout the day
  • redness of your eyes
  • watery eyes, particularly when you are exposed to wind
  • your eyelids are stuck together when you wake up 

Cataracts

If you have cataracts, your sight is likely to be affected by different light conditions. For example, you may find it more difficult to see:

  • if the light is dim
  • when the light is bright, such as on a very sunny day or in bright artificial light

Cataracts can also affect your sight in other ways, including:

  • The glare from bright lights may be dazzling or uncomfortable to look at.
  • Colours may look faded or less clear.
  • Reading, watching television or other daily activities may become more difficult than they used to be.

Macular degeneration

The macular is located at the centre of the retina. The retina is the layer of light-sensitive tissue at the back of the eye that converts light into images and sends them to the brain.

The macular plays a very important role as it enables you to see what is directly in front of you and allows you to see things in close-up detail and in colour.

If the delicate cells of the macula are damaged and stop working properly, your vision will be affected. This can sometimes occur as a person gets older and is commonly known as age-related macular degeneration (AMD).

There are two types of AMD, called dry AMD and wet AMD:

  • Dry AMD is the most common type of AMD, and gradually causes a loss of your central vision.
  • Wet AMD is more serious than dry AMD. It often develops very quickly and is caused by new blood vessels growing behind the retina, which leads to bleeding and scarring. Wet AMD requires treatment as soon as possible.

Dry AMD

If you have dry AMD, you will:

  • need brighter light than normal when reading
  • find it difficult to read printed or written text (because it appears blurry)
  • have difficulty recognising people's faces

Your vision will seem hazy or less well defined, and colours may also appear less vibrant.

Wet AMD

If you have wet AMD, you will have:

  • visual distortions, for example straight lines may start to appear wavy or crooked (metamorphopsia)
  • a blind spot, which usually appears in the middle of your visual field (scotoma) and will become larger if left untreated

Seek immediate medical assistance if you or someone you know experience any sudden changes in vision, such as those described above.

Acute
Acute means occuring suddenly or over a short period of time.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

Despite improved access to treatment over recent years, cataracts are still the leading cause of visual impairment in all areas of the world (apart from in developed countries).

In the least developed countries - in particular, those in sub-Saharan Africa (countries to the south of the Sahara desert) - the causes of avoidable blindness are:

  • cataracts (50%)
  • glaucoma (15%)
  • corneal opacities (10%)
  • trachoma (7%)
  • childhood blindness (5%)
  • onchocerciasis (4%)

The World Health Organization (WHO) is aiming to eliminate avoidable blindness by 2020 and has introduced a global initiative called VISION 2020: The Right to Sight. In particular, the strategy aims to target the six conditions listed above. 

Chronic blindness

Chronic (long-term) blindness can be caused by a number of different health conditions. For example, it can be caused by:

  • cataracts, where a cloudy area forms in the lens of the eye
  • glaucoma, a group of eye conditions that affect your vision
  • age-related macular degeneration, where the vision gradually deteriorates with age (see below)
  • corneal opacities, where continual scratching of the cornea (the transparent window at the front of the eye) causes it to become inflamed and then opaque (cloudy)
  • diabetic retinopathy, where the tiny blood vessels that nourish the retina become damaged
  • trachoma, a bacterial eye infection
  • childhood eye conditions, such as those caused by vitamin A deficiencies, for example corneal scarring and visual loss

Sometimes, blindness can also be caused by injury or trauma to the eyes.

Age-related macular degeneration (AMD)

In Ireland, age-related macular degeneration (AMD) is the most common cause of visual impairment among older people.

About 2% of people who are over 50 years of age have AMD. This rises to 8% of people over 65, and 20% of people over 85.

The exact cause of AMD is unknown. However, a number of risk factors have been identified that will increase your chances of developing the condition. These are listed below.

  • Age: as you get older, your chances of developing AMD increase.
  • Sex: women are more likely to develop AMD than men.
  • Genetics: a number of genes have been identified which, if inherited (passed on from a family member), may increase your likelihood of developing AMD.
  • Smoking: if you smoke, you are more likely to develop AMD.
  • Sunlight: prolonged exposure to sunlight may affect your retina. To protect your eyes, always wear a pair of good-quality sunglasses in bright conditions.

Vitamin and mineral supplementation

Certain types of vitamins and minerals may also provide some protection against the effects of AMD.

For example, studies have shown that dietary supplements that contain high amounts of vitamin A, C, E, and beta-carotene may help slow the progression of AMD. The minerals zinc and copper have also been shown to have a positive effect.

However, only take vitamin and mineral supplementation if you are advised to by a doctor or eye care specialist, and it is only recommended for people who are classed as being at high risk, such as those who already have AMD in one or both eyes.

Aching
An ache is a constant dull pain in a part of the body.
Blood vessel
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
Deficiency
If you have a deficiency, you are lacking in a particular substance needed by the body.
Double vision
Double vision means seeing two images of a single object instead of one.
Genetic
Genetic is a term that refers to genes, the characteristics inherited from a family member.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

When you have your eyes tested, your optometrist will carry out a number of different tests to determine whether you need glasses and, if so, what type of lenses you need. They will also check your vision and the overall health of your eyes.

The types of test you may have are described below.

Snellen test

The Snellen test is used to determine how good your vision is. During the test, you will be asked to read from a letter chart that has an illuminated background and rows of black letters that get progressively smaller on each line. This is the conventional type of Snellen chart, but some optometrists may use slightly different versions of it.

If you wear glasses or contact lenses for distance vision, take them with you when you go for a sight test. You may be asked to read from the Snellen chart while you are wearing your glasses or contact lenses. Your optometrist will also take into account how far away from the chart you are when you are reading the letters.                                         

Further eye tests

If you do not currently wear glasses or contact lenses and your optometrist decides that you need to wear them, you will need to have further tests to determine what kind of glasses (or lenses) you need. During these tests, you will be asked to wear a number of special lenses and to look at various charts displaying different letters and colours.

Your optometrist will shine a light into each of your eyes to examine the back of your eyes and check for signs of eye conditions, such as glaucoma (a progressive eye condition that affects vision) and diabetic retinopathy (damage to the tiny blood vessels that nourish the tissues of the eye).

At the end of your eye test, your optometrist will discuss the results with you and advise you about the best course of action. They will also either give you a certificate to confirm that you do not need to wear glasses or contact lenses, or a prescription for the type of glasses or lenses you need. The prescription can be used at any optician.

Registering as blind or partially sighted

If, during your sight test, you can only read the top line of the eye chart, you may be eligible to register as blind or partially sighted. To do so, you will need to be referred to an ophthalmologist (a specialist in diagnosing and treating eye-related conditions) by your GP or optometrist.

After carrying out further tests, the ophthalmologist will write to your local social services department to confirm that you have been diagnosed as blind or partially sighted. You may also be registered as blind or partially sighted if you are able to read the first three lines of the chart but you have a severely restricted field of vision (you are unable to see to the side).

Other vision tests

If you have a high risk of developing eye conditions such as glaucoma or diabetic retinopathy, or if your optometrist has found signs of these conditions, you may need to have some more vision tests. Some of the vision tests you may need to have are described below.

Visual field test

A visual field test is used to measure your peripheral (sideways) vision using a piece of equipment called a visual field screener. During the test, you will be asked to look at a small point in the middle of the screen (while keeping your eye still).

At random intervals, a light will flash on and off at different places on the screen around the central point. Each time you see the light flashing, you will be asked to respond by pressing a buzzer. The lights may also be of varying brightness.

The test will then be repeated with the other eye covered.

Tonometry

Tonometry is one of the tests used to detect glaucoma. It involves using an instrument called a tonometer to measure the pressure inside your eyeball.

The optometrist or ophthalmologist will hold the tonometer close to your eye and will press a button to release a small puff of air against your eyeball. The tonometer has a sensor which measures how much indentation the air has caused. The procedure is painless, but it may cause a very small amount of discomfort.

Ophthalmoscopy

Ophthalmoscopy is a test that is used by an eye care professional to examine the inside of your eye in detail, including the retina (the light-sensitive layer of cells that line the back of the inside of the eye) and the optic nerve (the nerve that connects your eye to your brain).

Ophthalmoscopy may be carried out using a bright light and a lens that is held in front of your eye, or a torch that is held very close to your eyeball.

Treatment for impaired vision will depend on the specific eye-related problem that you have. A number of treatments for some of the most common eye conditions are described below.

Glaucoma

It is very important that glaucoma is diagnosed at an early stage so that it can be treated and prevented from developing further. The aim of treatment for glaucoma is to reduce the pressure in the affected eye.

Chronic glaucoma

Eye drops are often used to treat chronic (long-term) glaucoma. There are many different types of eye drops, some of which are listed below:

  • Beta-blockers help reduce the amount of fluid produced in your eyes. However, they should not be used if you have asthma or heart disease because they can make these conditions worse.
  • Alpha agonists help reduce the amount of fluid produced in your eyes, as well as improving the flow of fluid out of your eye. They are not recommended for children because they can cause nightmares.
  • Prostaglandin or prostamide analogues help improve the flow of fluid out of your eye. Side effects include pinkness of the eye, which may last for several days.
  • Carbonic anhydrase inhibitors help reduce the amount of fluid produced in your eyes. These drops may cause a bitter taste in your mouth.
  • Cholinergic agonists help the fluid to flow out of your eye more effectively. These eye drops may cause headaches, eye ache and dark or blurred vision.

If eye drops do not improve chronic glaucoma, laser treatment or surgery may be recommended. There are several options:

  • Trabeculectomy is the most common form of glaucoma surgery. It involves making a small channel through the white part of the eye to allow fluid to flow out of your eye.
  • Laser treatment can be used to open up the blocked drainage system in your eye. The procedure is usually quick and painless, although you may experience mild discomfort.
  • Viscocanalostomy involves removing part of the sclera (the white, fibrous outer layer of the eyeball) to enable fluid to filter out of your eye and into your body.
  • Deep sclerectomy involves implanting a tiny silicone device to open up the drainage canal in your eye.

Acute glaucoma

Acute (short-term but severe) glaucoma develops rapidly, so the condition needs to be treated quickly. The most common treatments for this type of glaucoma include:

  • eye drops (see above for details)
  • systemic medicines, which are injected into your bloodstream and quickly reduce the pressure in your eye
  • laser treatment to create a hole in your iris (the coloured part of the eye) to help maintain some vision. As acute glaucoma almost always develops in both eyes at some point, both eyes will need to be treated, even if only one is currently affected
  • surgery, the most common type being trabeculectomy (see above for details)

For more information about treating both chronic and acute glaucoma, see the Health A-Z topic about Glaucoma - treatment.

Dry eye syndrome

Some people with dry eye syndrome have recurring episodes of the condition for the rest of their lives. There is no cure, but a range of treatments, such as eye drops, can help control your symptoms. In severe cases of dry eye syndrome, surgery is required.

When treating dry eye syndrome, an ophthalmologist (eye specialist) will try to identify any possible triggers that are causing the condition, such as medicines or environmental factors. They will then attempt to eliminate them.

If an environmental factor is triggering your dry eyes, such as a particularly dry atmosphere, your ophthalmologist may recommend placing a humidifier in your home or workplace, to help reduce the dryness. If another health condition is triggering your dry eyes, this will also be treated.

Mild to moderate cases of dry eye syndrome can usually be successfully treated using eye drops that contain tear substitutes (a liquid that mimics the properties of tears). These eye drops are available over-the-counter (OTC) from a pharmacy without a prescription. Your GP or pharmacist will be able to recommend the most appropriate drops for you.

If your eyes fail to respond to other forms of treatment, surgery may be an option. One surgical technique, known as punctual occlusion, involves using small plugs to seal your tear ducts, which help keep your eye protected by tears.

Initially, to determine whether the operation will succeed, temporary plugs made of silicone are used. If these work, the silicone plugs can be replaced by more permanent ones.

See the Health A-Z topic on Dry eye syndrome - treatment for more information.

Cataracts

Most cases of cataracts are treated with surgery. See the Health A-Z topic about Cataract surgery for more information. There are two different kinds of cataracts:

  • age-related
  • childhood

These are described in more detail below.

Age-related

In the early stages of a cataract, wearing stronger glasses or using a brighter light (for example, to read) may help improve your vision. However, in more severe cases, surgery will be required.

Surgery involves removing the cloudy lens in your eye. In most cases, the natural lens is replaced with a clear, plastic lens. This is called an intraocular implant or intraocular lens (IOL).

In Ireland, most cataract operations are carried out under local anaesthetic using keyhole surgery. You will not usually need to stay in hospital overnight as you will probably be admitted as a day patient (day case).

A procedure called phacoemulsification, also known as phaco extracapsular extraction, is the most common operation used for treating cataracts. See the Health A-Z topic on Age-related cataracts - treatment for more information about phacoemulsification and other types of cataract removal surgery.

After cataract surgery, there is usually an immediate and noticeable improvement in your vision, although it may take a little while to settle down completely. You will probably need to wear glasses, either for distance vision or near vision. If you wore glasses before your operation, your prescription will probably change.

Childhood

If your baby or child has cataracts, whether or not they will need treatment will depend on whether one or both eyes are affected and how mild or severe their cataracts are.

Childhood cataracts may be treated by:

  • using surgery to remove the cloudy lens and replacing it with an artificial lens
  • wearing glasses
  • wearing contact lenses
  • a combination of these treatments

If your baby's condition is present from birth (congenital), they will probably need surgery a few weeks after they are born.

After the operation to remove your child's cataract(s), you will be given eye drops to give to your child at home. This will help reduce any inflammation (swelling).

Your child will need to return to hospital for regular check-ups and vision tests. They may also need to wear glasses or contact lenses and, if one eye is stronger than the other, they may need to wear a patch over the weaker eye (occlusion therapy).

See the Health A-Z topic on Childhood cataracts - treatment for more information.

Macular degeneration

Dry AMD

There is currently no cure for dry age-related macular degeneration (AMD). With dry AMD, the deterioration of vision is very slow. You will not go completely blind and your peripheral (outer) vision should not be affected.

You may be referred to a low-vision clinic, which can provide useful advice and practical support to help minimise the effects of dry AMD. For example, you may be advised to try:

  • magnifying lenses
  • large-print books
  • bright reading lights

Wet AMD

A number of treatments can help stop the progression of wet age-related macular degeneration (AMD). It is very important that treatment is started as soon as possible, because once your sight has been lost, it cannot usually be restored.

Photodynamic therapy (PDT) involves injecting a light-sensitive medicine called verteporfin into into a vein in your arm. A low-powered laser is then shone into your damaged eye, which activates the verteporfin. The verteporfin destroys the abnormal vessels in your macula (the part of your eye responsible for central vision) without harming the other delicate tissue in your eye.

You may need to have PDT every few months to ensure that any new blood vessels that start growing are kept under control. PDT is not a suitable treatment for everyone. It will depend on where the blood vessels in your eyes are growing and how severely they have affected your macula.

Anti-VEGF medication is a newer type of treatment. It blocks a chemical called vascular endothelial growth factor, stopping it from stimulating the growth of blood vessels in the eye that cause wet AMD.

Some research has found that high doses of vitamins A, C, E, beta-carotene and the mineral zinc may slow the progression of AMD. However, only take vitamins and minerals if recommended by your GP or ophthalmologist. They may do more harm than good if the correct dose is not taken.

See the Health A-Z topic on: Macular degeneration - treatment for more information about the treatment options for dry and wet AMD.

Regular eye examinations

It is very important to have regular eye examinations to stop your eyes becoming damaged by undiagnosed conditions.

Most people should have their eyes tested at least once every two years, but if you have a health condition, such as diabetes, glaucoma or high blood pressure (hypertension), you will probably need to have them tested more regularly. Your optometrist can advise you about how often to have your eyes tested.

It is very important for drivers and people whose eyesight may be affected by their occupation, such as those who use computer monitors, to have regular eye examinations.

Children should also have regular eye examinations. This is because it is very important that visual problems are diagnosed early so that learning and other developmental problems can be prevented.

The Health Service Executive (HSE) is obliged to provide optical services free of charge to certain groups. These services may be provided by Health Service Executive (HSE) staff or by private practitioners.

Adults

  • Medical card holders
  • and their dependants
  • People with Hepatitis C who contracted the disease through the use of Human Immunoglobulin-Anti-D or from receiving any blood product or a blood transfusion within Ireland and who have a Health Amendment Act Card

Only vision tests and standard prescription spectacles (where required for medical rather than cosmetic reasons) are free of charge to adults in the groups listed above.

Children

Pre-school children and national school children referred from child health service and school health service examinations who are discovered to have sight problems are referred to the appropriate consultant for treatment. If this treatment is carried out at the out-patient department of a public hospital, the service is free and no hospital charges have to be paid. Services in these circumstances, will continue to be provided until the child has reached the age of 16.

Rates

You will not have to pay for optical services if you are among the qualifying groups above.

If you are not among the qualifying groups, the Treatment Benefit Scheme may cover you and your dependent spouse for certain free optical services. If you do not have enough social insurance contributions, you may have to pay for these services.

You may however be able to claim tax relief for medical expenses that are incurred by your spouse (and certain other relatives) as a result of specific optical treatments. These optical treatments must be prescribed by your practitioner.

It's important to be aware that charges for spectacles, lenses and contact lenses can vary considerably, depending on your choice and your practitioner.

How to apply

If you are among the groups that qualify for free services, you should apply to your Local Health Office, health centre or clinic for a vision test. You may be referred by your family doctor (GP) for tests and treatment. The HSE then decides whether to send you to their own clinics or to a private practitioner.

Optometrists and dispensing opticians practising in Ireland must be registered with the Opticians Board. Opthalmologists must be registered with the Irish Medical Council.

You can check that your practitioner is registered with the relevant body. If you wish to make a complaint about a practitioner, you should contact the appropriate regulatory body under the heading "Where to apply".

Where to apply

Irish Association of Dispensing Opticians Ltd.
PO Box 9013
12 Pembroke Road
Ballsbridge
Dublin 4
Ireland
Tel: 01 668 0566
Web: http://iado.ie/index.php?page=home.php
Email: info@iado.ie

The Department of Social Protection has a list of available Opticians under the Treatment Benefits Scheme.

Other recommendations

There are several other ways to reduce the risk of visual impairment:

  • Protect your eyes from the sun. Ultra violet (UV) rays from the sun can damage your eyesight so in bright sunlight, wear a pair of good-quality sunglasses that protect your eyes from both UVA and UVB rays.
  • Find out whether there is a history of glaucoma or eye disease in your family. Have your eyes tested regularly if you have close relatives who have been diagnosed with glaucoma.

See your GP or your optometrist as soon as possible if you experience any changes to your vision or you have pain in or around your eyes.

If you smoke, giving up will significantly reduce your chances of developing problems with your vision. People who smoke are up to three times more likely to develop cataracts than non-smokers due to the chemicals found in cigarette smoke.

Hypertension
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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