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What it is: Cataract is clouding of the lens of the eyes which prevents clear vision. Although it forms slowly and does not cause symptoms like pain, redness or tearing in the eyes, it is the leading cause of blindness in Africa and worldwide. According to the WHO, cataract is responsible for 51% of world blindness, which represents about 20 million people in 2010 with around 3.5 million in Africa.
How it is caused: Age is an important risk factor in the causation of cataract. It may also develop after eye injuries, inflammation, exposure to environmental hazards and other eye and systemic diseases like diabetes mellitus. Occasionally children can be born with the condition.
Prevention and Treatment: Reduction of cigarette smoking and exposure to ultraviolet radiation through the wearing of sunglasses may prevent or delay the development of cataract. Early detection and management of risk factors like diabetes mellitus and reduction of body mass are important prevention strategies.
Treatment of cataract is surgical and very successful in restoring sight. The cloudy lens is removed and replaced by an artificial .intraocular lens. In many remote parts of Africa, people remain blind from cataract due to lack of eye care.
What is it: Onchocerciasis also known as ‘River blindness’ is the world’s second leading infectious cause of blindness. A total of 18 million people are infected with the disease worldwide, with 40,000 new cases added each year. 99% of infected people live in Africa and at least one million are either blind or severely visually disabled.
How it is caused: Onchocerciasis is caused by a parasite Onchocerca volvulus and transmitted by blackflies of the species Simulium damnosum that abounds in fertile riverside areas. O. volvulus is a parasite of man. Adult worms live in nodules in the skin of a human body where female worms produce high numbers of first-stage larvae known as microfilariae. The microfilariae find their way to the eyes where they cause eye inflammation, bleeding, and other complications that ultimately lead to blindness.
Prevention and Treatment: Public health intervention directed at controlling the sandfly has helped to prevent and in some cases eradicate the disease in endemic areas. The disease can be treated with a drug called ivermectine, This drug also relieves the severe skin itching caused by the disease.
What it is: Refractive errors are eye disorders caused by irregularity in the shape of the eye. This makes it difficult for the eyes to focus images clearly, and vision can become blurred and impaired. Refractive errors include myopia (short-sightedness), and hyperopia (long-sightedness) with or without astigmatism (when the eye can sharply image a straight line lying only in one meridian). Recent WHO data indicates that severe refractive errors account for about 5 million blind people worldwide with an estimate of 124 million people in the world suffering from low vision. The burden of refractive errors in African children of school age is quite high.
How they are caused: Refractive errors are caused by abnormal shape and texture of the eyes. Risk factors include family history, excessive eye strain, eye trauma or eye surgery, excessively thin cornea (the thin and clear covering in front of the eyes) and lens, as well as systemic disorders like diabetes mellitus that afflict the eyes and changes its shape.
Prevention and Treatment: Get an eye exam once yearly to pick up early onset of refractive errors. Eating fresh fruits and vegetables that are rich in vitamins A and C may help with vision. Foods such as sweet potatoes and carrots are rich in good nutrients for the eyes. Wear UVA and UVB protective dark sunglasses when outside. Decrease eye strains by resting your eyes after long periods of reading or sewing for example. Change your glasses or contact lenses as often as your eye care services provider recommends.
Treatment includes wearing of suitable eye glasses or contact lenses to help correct the shape of the eyes. This helps light to focus correctly and improves vision. Eye drops or ointments may be needed to contain inflammation and help eye muscles get stronger so as to improve focus. Cost and lack of skilled providers are obstacles to basic refractive error eye care in Africa. In certain circumstances, surgery may be needed to reshape the curve of an affected cornea. Ask your eye care services provider for more information on refractive surgery.
What it is: Individuals with bad or poorly managed diabetes mellitus for several years suffer from damage of variable severity to blood vessels and the sensitive tissue of the eyes called the retina. This tissue contains pigmented and nerve cells that afford us vision. Diabetic retinopathy degrades vision and may cause irreversible blindness. It is estimated that 1 in 3 people with diabetes mellitus suffer from diabetic retinopathy in Africa with an estimated total of 93 million sufferers.
How it is caused: Diabetic retinopathy is considered to be the result of vascular changes in the blood vessels that supply the retina. In the early stages narrowing, weakness, dilatation and micro-bleeding occurs in the vessels. This may progress with the growth of new blood vessels that also have weak walls and bleed easily. Macular oedema (the thickening of the central part of the retina) can also occur. The end result of these processes is significant damage to the retina with decrease in visual acuity or total blindness.
Prevention and treatment: Control risk factors for diabetic retinopathy as they exist through lifestyle changes with or without medication. These risk factors may include duration of diabetes, level of raised sugar in blood, presence of high blood pressure, dependence on insulin, pregnancy, levels of selected serum lipids, nutritional and genetic factors. If sight-threatening retinopathy is present, timely specialized surgery (laser photocoagulation) of the retina decreases the risk of subsequent severe visual lesion with vision loss.
What it is: Glaucoma is a condition of increased pressure in the fluid (aqueous humor) contained in the front of the eye. It causes sudden or progressively worsening damage to the nerve that transmits images to the brain (the optic nerve). It is the second leading cause of blindness worldwide and accounts for about 15% of blindness in Africa. There are several types of glaucoma. The two most common are primary open angle glaucoma (POAG), having a slow and subtle onset, and angle closure glaucoma (ACG), which is less common and tends to be more sudden in onset.
How it is caused: In theory, any factor that causes increased production or reduced drainage of the fluid in front of the eyeball can cause glaucoma. Sometimes, the exact reason for pressure build up is known. Risk factors for glaucoma and its severity in people of Africa include age of onset, heredity, presence of diabetes mellitus, use of certain medication, trauma, poor awareness of the condition, low access to eye care services, poor quality of services provided, and adherence to treatment and follow-up.
Prevention and treatment: Little is known about primary prevention of glaucoma. But effective medical and surgical treatments are available. Your doctor may prescribe eye drops that help to reduce pressure within the eye by reducing fluid production or increasing fluid drainage. Surgical treatments include specialized laser or microsurgical procedures. The outlook for glaucoma care in Africa is good if the condition is seen early and quality eye care services are accessible, affordable and provided.
What it is: Age-related macular degeneration (AMD) is a condition affecting older people above age 60 years. It is a leading cause of irreversible vision loss and involves the loss of the person's central field of vision. It occurs when the macular (or central) retina deteriorates. The retina is the light sensing nerve tissue of the eye. Several forms of AMD exist. Symptoms of macular degeneration include:
How it is caused: It is thought that reduction in the blood flow to the macular area of the retina plays a part in the causation of this disease. Factors contributing to the risk of having the disease include, smoking, high blood pressure, obesity, high cholesterol, being a woman, being light skinned, heredity, etc.
Prevention and treatment: At present, there is definitive no cure for the disease. The focus of treatment is to prevent severe vision loss and slow progression of the disease. Treatment options currently available include: use of special drugs injected into a chamber of the eye (intravitreous injection), lasers, dynamic phototherapy and sometimes surgery. Early rehabilitation for those with the disease includes psychological support, mobility and life skills for independent and full life quality experience as well as adaptation of the living and work places. The use of special aids for reading and computer use are also recommended.