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.
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.
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.
Causes of visual impairment
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 (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 the UK, 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.
Information taken from NHS UK
Image credit: d ha rm e sh