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Visual Impairment

What is It?

boy using a device to feel the ground as he walks

Vision Impairments are placed on a broad range. Visual Impairments include being completely blind, having low vision, or not being able to see certain colors. Vision is measured with two main methods, the Snellen test and visual field testing. The Snellen test measures the sharpness of your vision. The Snellon test involves reading off a chart with letters that decrease in size each line. After the test, two numbers are given. The first number is how far away (meters) from the chart you were able to read the letters, the second number is the number someone with healthy eyesight would get if they took the test. Visual field testing tests your peripheral vision. As you look straight ahead, lights are flashed in your peripheral vision and you will be asked to push a button when you see the light flash. Visual field testing checks for gaps in your field of vision.

Signs of Visual Impairment

Early signs and symptoms in babies may include jerky, quick side-to-side, or wandering eye movements, lack of eye contact, being unable to follow moving objects with his/her eyes, eyes don’t dilate correctly, pupils that are white or cloudy instead of black, or eyes that don’t line up (cross eyed or lazy eyed).

Older children with Visual Impairment might hold items close to their face, rub eyes often, turn, tilt, or cover an eye when looking at items near to them, get tired after looking at close objects, seem to have better day than night vision, say their eyes are tired, have misaligned or squinty eyes, or seem clumsy and fall over items often.

Causes of Visual Impairment

Visual Impairment can be caused by Macular Degeneration, Cataract, Glaucoma, Diabetic Retinopathy, Strokes, High Blood Pressure, Multiple Sclerosis, Retinitis Pigmentosa, trauma, or injury. Other causes include neurological conditions that affect the occipital lobe and nerves connected to vision, genetics such as Albinism, illnesses that premature babies get or when there are other birth complications, or if a mother is infected by a certain virus while pregnant.


Over 285 million people in the world are visually impaired, of whom 39 million are blind and 246 million have moderate to severe visual impairment (WHO, 2011).

It is predicted that without extra interventions, these numbers will rise to 75 million blind and 200 million visually impaired by the year 2020 (WHO, 2010).

Among persons who are blind worldwide:

  • 58% are age 60+
  • 32% are ages 45-59
  • 7% are ages 15-44
  • 4% are age 14 or under (Thylefors, et al., 1995)
  • The number of people with partial sight today - 135 million - is expected to double by the year 2020 (Vision 2020, 2000).
  • 90% of the world's blind live in a developing country (WHO, 2010).
  • Globally, about 85% of all visual impairment and 75% of blindness could be prevented or cured worldwide (WHO, 2010).
  • South East Asia and Western Pacific account for 73% of moderate to severe visual impairment and 58% of blindness (WHO, 2011).

References and Websites

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