According to World Health Organization (WHO), the causes of blindness differ significantly in developed and developing countries. The difference basically lies in the availability or non-availability of modern surgical technology, health infrastructure and the level of awareness of availability of treatment options among the people.
Following is the list of top five causes of blindness worldwide:
1. Cataract: With 47.9 percent of all causes of blindness, cataract tops the chart in all parts of the world except for the developed countries. Cataract is mostly age-related and is common in old age group. Cataract causes cloudy vision which usually becomes worse progressively. If not treated, cataract causes complete blindness eventually. With modern surgical techniques, cataract can be removed and vision can be restored to normal if there are no associated ocular diseases.
2. Glaucoma: It the next most common cause of blindness (12.3 percent). The most common type of glaucoma is Primary Open Angle Glaucoma (POAG). In the initial stages, there may not be any symptoms and the disease may be discovered during routine eye examination or in late stages when a lot of damage has already occurred. Unlike cataract, the blindness caused by glaucoma is generally irreversible.
3. Age-related Macular Degeneration (AMD): As the name implies, it is age related and the blindness results from degeneration of the macula which is the central part of retina. Its prevalence throughout the world is 8.7 percent.
4. Corneal Opacities: With its share of 5.1 percent, it is the fourth most common cause of blindness worldwide. A corneal opacity is a scar in the otherwise transparent cornea which is the most anterior tissue to refract the light. Any partial or complete opacity in the cornea results into blurred vision or complete blindness respectively. The most common causes of corneal opacities are the infections of cornea.
5. Diabetic Retinopathy: 4.8 percent of the blindness worldwide is caused by affliction of retina in diabetic patients. With rising incidence of diabetes especially in the developed countries, diabetic retinopathy is among the top five causes of blindness.
It is important to note that in the above list, all of them are ‘avoidable’ causes of blindness except for age-related macular degeneration which generally cannot be avoided and has a poor prognosis.