Low vision is the loss of sight that is not correctible with prescription eyeglasses, contact lenses or surgery. This type of vision loss does not include complete blindness, because there is still some sight and it can sometimes be improved with the use of visual aids.

Low vision includes different degrees of sight loss, from blind spots, poor night vision and problems with glare to an almost complete loss of sight. The American Optometric Association defines low vision as two categories:

• “Partially sighted”: the person has visual acuity between 20/70 and 20/200 with conventional prescription lenses.
• “Legally blind”: the person has visual acuity no better than 20/200 with conventional correction and/or a restricted field of vision less than 20 degrees wide.

The ratio measurement of vision describes visual acuity, or the sharpness of vision, at 20 feet from an object. For example, having 20/70 vision means that you must be at 20 feet to see what a person with normal vision can see at 70 feet.