18 June 2019
Visual impairment on a global scale
Out of 7.5 billion people in the world, over 285 million are visually impaired. Of these 285 million, 246 million have low vision, and 39 million are blind. 80% of these forms of visual impairment are actually preventable or curable (and are usually treated in developed countries) meaning that, sadly, 90% of people affected live in developing countries. More developed countries have the money and resources to treat those in need and, in many cases, restore their sight. Globally, two thirds of people suffering from a visual impairment are female, and 82% of blind people are aged over 50. The leading causes of blindness around the world are:
- Cataract – 39%
- Refractive errors – 18%
- Glaucoma – 10%
- Age-related macular generation – 7%
- Corneal opacities – 5%
- Diabetic retinopathy – 4%
- Other – 17%
Cataracts affect around 65 million people worldwide, causing over a third of global blindness and rendering around 13 million people totally blind. A further 52 million people experience some form of vision loss due to cataracts, and 99% of these people live in developing countries. Cataracts are treatable and treatment is usually accessible in developed countries, which is why it rarely causes blindness there. In fact, cataract surgery is performed 18 million times around the world each year. Developing countries have such high cataract-blindness rates because treatment isn’t as available or affordable. For instance, cataracts are responsible for 50-80% of blindness in India, and 65% in Africa.
Cataracts are nearly always age-related and, as global life expectancy increases, they become a more prevalent problem. Further to this, studies have shown that the highest risk groups for developing cataracts are those from African or Latino backgrounds. Several eye charities and even individual cataract surgeons travel to developing countries to set up cataract clinics, treating those in need free of charge. A large part of the problem is countries’ access to qualified professionals, so addressing this issue should begin to make cataract surgery more accessible in areas that need it most.
Trachoma is a bacterial eye infection which causes inflammation on the inside of the eyelids. It can cause the upper eyelid to turn inwards and, over a longer period of time and repeated infection, it can cause severe scarring on the eye and lead to irreversible blindness. Trachoma is contagious and 80 million people worldwide suffer from it. 99% of these live in Sub-Saharan Africa and, although currently uninfected, a further 180 million people live in areas where Trachoma is widespread – and therefore are at high risk. It is a public health problem in 37 countries and responsible for the total blindness of around 2 million people globally.
Trachoma is hyperendemic in particularly disadvantaged and rural areas in Africa, Central and South America, Asia, Australia and the Middle East. Africa is the continent which suffers the most with infection. It spreads through personal contact – and therefore is particularly high among children – and by flies which carry the infection. Trachoma can be treated by antibiotics but, in developing countries, these aren’t always easily accessible. Charities usually have to step in, or people rely on donations from drug manufacturers to fight the condition. Surgery is also recommended for advanced stages of trachoma, but it won’t help people who have already been blinded by the condition. Long term, improvements to water supply and overall sanitation must be made to prevent the spread of trachoma.
Glaucoma is where the eye’s pressure increases and begins to cause damage to the optical nerve, eventually leading to vision loss. Symptoms usually begin with the loss of peripheral vision before central vision becomes affected too. Glaucoma accounts for 10% of blindness globally (around 4.5 million people), while the total number of cases is expected to rise to around 80 million by 2020. There are two types of glaucoma: primary open angle glaucoma (POAG) and angle closure glaucoma (ACG). POAG occurs more in older people and is most common with people of African origin. ACG is less common overall, and is usually more acute, but it is most common in people of Asian origin. Glaucoma tends to run in families so if people are aware of their family history, it can help early diagnosis and allow the patient to begin timely treatment.
Much like with trachoma and cataracts, the number of people suffering from glaucoma in developing countries is made worse by the lack of trained ophthalmologists. In Europe, there is one ophthalmologist for every 10,000 people; in India the figure is 1 for 400,000, while in Africa it’s one for every million people. The first step in tackling the high prevalence of glaucoma developing countries is to provide training and education in order for ophthalmologists to qualify. Education in how to reduce your risk factor for glaucoma should also be implemented, such as understand the links between high blood pressure and high eye pressure, resulting in glaucoma.
Age-related macular degeneration (AMD)
In high-income countries, AMD is the leading cause of blindness (while in developing countries it is cataracts) accounting for 7% of global blindness. This is because cataracts can be treated with a simple lens replacement, while there is no cure as yet for AMD. This isn’t to say that people in developing countries don’t develop AMD; just that untreated cataracts are more common and therefore are a more prevalent issue. Globally, AMD is the third-leading cause of blindness after cataracts and glaucoma. Studies have shown that people with Caucasian backgrounds are more likely to suffer from AMD than those from African or Asian backgrounds. Further studies found “significantly more AMD in white patients than in black patients” and that AMD is much more likely to affect those with blue or hazel coloured irises. Countries with populations with lighter coloured eyes suffer from AMD disproportionately more than countries where the majority of the population have brown eyes.
Treatments for AMD include intra-vitreous drugs, lasers, phototherapy and sometimes even surgery; however these can only slow the process of its development and do not act as a cure. AMD first affects a person’s central vision so they may have trouble reading or recognising faces, but are fine when walking around. In this sense, in the early stages at least, a person’s mobility isn’t as badly affected as with other conditions such as cataracts. Education is vital in preventing the development of AMD, making sure that people are aware of the risk factors. These include smoking, consuming a non-balanced diet, and exposure to UV rays, as well as genetic tendencies which, sadly, people can’t do much about.
What’s your risk factor?
Certain conditions are more common in particular ethnicities and it’s important to know what you’re at the highest risk of developing, and recognising the symptoms. Certain parts of the world, particularly Africa, are high-risk areas for trachoma, so taking precautions to deter trachoma-carrying insects, drinking only clean water, and observing basic hygiene should lower your risk considerably. Attempting to lower your risk factor by quitting smoking, drinking, and eating a healthy diet also goes a long way. Read our articles on eye health and the eye’s ageing process to understand what you can do to preserve your eyesight in years to come.