Vision impairment may be caused by a loss of visual acuity, where the eye does not see objects as clearly or sharply as usual. A person with a visual acuity of 20/70 can see at 20 feet what someone with normal sight can see at 70 feet.
Vision impairment may also be caused by a loss of visual field, where the eye cannot see as wide an area as usual without moving the eyes or turning the head. A normal visual field is about 160-170 degrees horizontally.
As per the definition published by the World Health Organization, ‘low vision’ is visual acuity between 20/70 and 20/400, with the best possible correction, or a visual field of 20 degrees or less. ‘Blindness’ is defined as a visual acuity worse than 20/400, with the best possible correction, or a visual field of 10 degrees or less.
From the videos, we now know how our eyes are perceiving light, images, color, and motion in our surroundings, support in making 2D and 3D interpretations for the brain, and how an impairment in the vision affects this process.
Here’s a quick simulation activity to help you understand the experiences of different types of vision impairment.