low vision

Low vision in its simplest terms refers to vision that can longer be corrected to normal vision with eyeglasses, contact lenses, medication or surgery. The World Health Organization has this to say about low vision:
There are four levels of visual function, according to the International Classification of Diseases -10 (Update and Revision 2006):
1) normal vision
2) moderate visual impairment
3) severe visual impairment
4) blindness
Moderate visual impairment combined with severe visual impairment are grouped under the term “low vision”: low vision taken together with blindness represents all visual impairment.