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Blindness Resource Center

Visual impairment is total or partial vision loss. Blindness is the condition in which the vision is 20/400 or lower. A person may suffer from visual impairment due to some disease or trauma. Sometimes, it happens due to a medical condition which is not corrected in time. In case of low vision, the person cannot clearly see either the objects kept at a distance or close by. In many cases, the loss of vision cannot be corrected by contact lenses or eyeglasses. Some forms of partial or complete vision loss can be corrected by making refractive correction of eyes which is either done through medication or surgery.

Epidemiology 

According to the latest statistics of WHO, about 314 million people across the globe suffer from visual impairment out of which 45 million are completely blind. It has been found that 87% of the visually impaired are living in developing countries and about 85% of the cases are avoidable. Avoidable blindness is highest in South East Asia (28%) and Western Pacific (26%). It’s lowest in America (9.6%) and European nations (9.6%). Eighty percent of the people above 50 years suffer from some form of vision loss. The risk increases in people above the age of 65 and women are at a higher risk of losing vision. Color blindness is a genetic condition, and it is found in 8% of males and less than 1% of females. The main cause for visual impairment is cataract which is found in 39% of the cases, that is 17.6 million worldwide. The second major cause is refractive error which accounts for 18% of the cases.

Classification

Blindness is classified into three categories: total blindness, legal blindness, and low vision. Total blindness refers to lack of any form of visual perception, which is a severe condition. Legal blindness refers to vision acuity which is 20/200 or lower. People who are unable to read the biggest letters on charts even after using the corrective lenses are said to be legally blind. A condition called “low vision” refers to the visual acuity in which the person can see less than 20/60 and more than 20/200. On the other hand, color blindness, night blindness, and snow blindness are three medical conditions in which the person finds it difficult to see things clearly. In color blindness, the person is not blind but he/she finds it difficult to perceive certain colors. In night blindness, the vision reduces in low illumination. In snow blindness, the vision reduces due to exposure to ultra violet rays. Snow blindness is a temporary condition and it happens because the cells on the corneal surface swell.

Causes of Blindness

Blindness can be caused by age related macular degeneration, diabetic retinopathy, cataracts, and glaucoma. It happens because of infection to the cornea which turns white in color after an injury or infection. Eye injury is a common cause for blindness in people below 30 years as it can cause optic nerve hypoplasia which affects the functioning of nerve that sends signals to the brain. Injury to occipital lobe can make a person completely blind even if the eye is not injured. Blindness caused during birth or early childhood can be caused by Leber's congenital amaurosis. Sometimes, certain chemicals such as methanol can cause blindness. Methanol is found in methylated spirits and it’s taken as a cheap substitute for alcohol in some parts of the world. Methanol poisoning can cause eye impairment. Willful actions such as torture, act of vengeance or acid attacks can cause blindness as well.

Adaptive Techniques and Aids

For mobility, reading, and magnification, the visually impaired use a number of tools and aids such as using routes and white cane with a red tip. Some use the lighter identification cane and dogs. Guide dogs are trained dogs which can help their owners reach complex places. Some use the software designed from GPS technology for easy mobility. The software assists with orientation and provides easy navigation. A number of magnifying glasses are used to enable reading letters for people who are not totally blind and Braille can be used to read books. Reading machines are provided to convert speech to Braille. There’s even certain optical character recognition software which can be used to read and write.

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