Vision impairment is defined as the limitation of actions and functions of the visual system that cannot be corrected to normal vision, even when the person is wearing eyeglasses or contact lenses. Most people with vision impairment have some ‘usable vision’. Only a small percentage of persons with vision impairment are ‘blind’ and some of them may have light perception or the ability to tell whether light is on or not in a darkened room. Vision impairments may thus vary from mild to severe and a person’s vision can also be affected by daily factors such as fatigue and environmental conditions like lighting.