The eye is recessed within its orbit and shielded by the brow ridge, the eyebrows and the eyelashes. Bright light activates the constriction of the pupil and the squinting reflex to minimize the penetration of the sun's rays into the eye. However, the effectiveness of these natural defences in protecting against the dangers of UV radiation is limited under extreme conditions such as sunbed use or strong ground reflection from sand, water and snow. Acute effects of UV radiation exposure include photokeratitis and photoconjunctivitis. These inflammatory reactions are comparable to a sunburn of the very sensitive skin-like tissues of the eyeball and eyelids, and usually appear within a few hours of exposure. Both can be very painful, but are reversible and do not result in any long-term damage to the eye or vision. Extreme forms of photokeratitis are 'arc-eye' and 'snow blindness'.
Cataracts are the leading cause of blindness in the world. Proteins in the eye's lens unravel, tangle and accumulate pigments that cloud the lens and eventually lead to blindness. Even though cataracts appear to different degrees in most individuals as they age, sun exposure, in particular exposure to UVB, appears to be a major risk factor for cataract development.
Cataract is clouding of the lens of the eye which impedes the passage of light. Although most cases of cataract are related to the ageing process, occasionally children can be born with the condition, or a cataract may develop after eye injuries, inflammation, and some other eye diseases.
According to the latest assessment, age related cataract is responsible for 48% of world blindness, which represents about 18 million people. Although cataracts can be surgically removed, in many countries surgical services are inadequate, and cataract remains the leading cause of blindness. As people in the world live longer, the number of people with cataract is growing. Cataract is also an important cause of low vision in both developed and developing countries. Even where surgical services are available, low vision associated with cataract may still be prevalent, as a result of the long period spent waiting for operations and barriers to surgical uptake, such as cost, lack of information, and transportation problems.
Prevention and treatment
Comprehensive prevention of cataract development is not known yet. Reduction of cigarette smoking, ultraviolet light exposure, and alcohol consumption may prevent or rather delay the development of cataract. diabetes mellitus, hypertension and high body mass index are identified as additional risk factors. The treatment of cataract is an operation, which is very successful in restoring sight. The opaque lens is removed and replaced by an artificial intraocular lens. In many remote parts of the developing world, people remain blind from cataract, due to a lack of access to quality eye care at an affordable cost.
VISION 2020 role
VISION 2020 through its member organisations facilitates the availability of affordable and high quality cataract surgical services. In countries of Africa and Asia cataract accounts for at least half of all blindness, despite the known technology that can restore vision at an extremely low cost. Reducing the backlog of cataract-blind mainly requires training ophthalmic personnel, strengthening the existing health care infrastructure, affordable pricing, and the availability of surgical supplies.