Low Vision InformationDefinitions, devices, and resources pertaining to low vision.
Low vision is a term used to describe a permanent and significant loss of visual function, including either visual acuity (the ability to see detail), visual field (the ability to see a large area of about 175 degrees), or both. Low vision cannot be corrected with conventional glasses, contact lenses, surgery, or medication.
Low vision is not to be confused with legal blindness, which is defined in federal law as “central visual acuity of 20/200 or less in the better eye with the use of correcting lens. An eye which has a limitation in the field of vision so that the widest diameter of the visual field subtends an angle no greater than 20 degrees is considered to have a central visual acuity of 20/200 or less.”
A central visual acuity of 20/200 means that a person can only see visual detail, such as a letter or word, at a distance of 20 feet that can be seen by a normally sighted person at a distance of 200 feet.
Legal blindness is not necessarily the same as total blindness. All totally blind people are legally blind. Some legally blind persons who have some usable vision are considered to have low vision. There must be some usable vision remaining in the eyes to be considered low vision.
To be eligible for special education, a pupil must have a visual impairment that, even with correction, adversely affects a pupil's learning of curriculum. For educational purposes, the term visually impaired includes: 1) functionally blind students who, because of the severity of their visual impairment, rely basically on senses other than vision as their major channels for learning; and 2) low vision students who use vision as a major channel for learning. A visual impairment does not include visual perceptual or visual motor dysfunction resulting solely from a learning disability.
Low Vision Devices
Collaboration among all professional education and eye care staff in providing coordinated, comprehensive services is critical in achieving the greatest success for students with visual impairment.
Low vision devices work in one of several ways:
- Control the focus or image clarity
- Control illumination and contrast
- Control magnification or size of the image on the retina
Magnification can be achieved by:
- Relative distance (moving closer to the object)
- Relative size (physically enlarging the object)
- Optical (enlarging the image on the retina by passing it through a lens or group of lenses)
- Electronic projection magnification (enlarging the image on the retina, using projectors and/or computers)
Other kinds of valuable, nonprescription low vision devices are various hand magnifiers, focusable stand magnifiers, loupes, head-borne nonprescription aids, clip-on loupes for near vision, and a large variety of other monocular and binocular distance-vision devices in various magnification ranges and styles to fit individual needs.
Locating a Low Vision Specialist in Your Area
American Foundation for the Blind (AFB)
California Optometric Association
California Academy of Eye Physicians and Surgeons
California School for the Blind, Low Vision Clinic
A list of optometrists who have earned special recognition as diplomats in low vision is available by contacting:
American Academy of Optometry