Definition of Low Vision

Low vision is a significant reduction of visual function that cannot be fully corrected by ordinary glasses, contact lenses, medical treatment and/or surgery. Low vision affects people of all ages . . . in the home, on the job, and at school. About 14 million Americans have low vision. It impacts daily activities like reading, cooking, taking medication, and watching television. People with severe low vision may be classified as partially sighted and/or legally blind.

What People with Low Vision See

Family members or friends with normal vision have a hard time understanding what someone with low vision can see. Each picture below shows two children playing. Each picture looks different depending upon the cause of vision loss simulated.

Normal Vision This picture shows two children playing
Central Field Loss A hazy or dark hole appears in the center of objects Causes include macular degeneration and optic atrophy
Multiple field loss Scattered dark patches or holes appear around objects Causes include diabetic retinopathy, glaucoma, retinal detachment and trauma
Tunnel Vision Loss of peripheral vision causes a restricted field of vision. Objects in the center remain visible Causes include glaucoma, retinitis pigmentosa and stroke
Some additional symptoms may include: Blurred vision Objects appear out of focus Causes include macular degeneration, diabetic retinopathy, cataracts or corneal disease

If you have (or someone you know has) any of these or other symptoms of vision loss, you (he/she) may benefit from vision rehabilitation programs. Please call us at 312-321-1470 to arrange an appointment for a low vision evaluation.

Vision Definitions

General Terms

• Partially sighted--best-corrected visual acuity of 20/70 or worse in the good eye. Even when wearing regular corrective lenses, partially sighted people cannot read standard newsprint, or see expressions on a person's face.
• Legally blind--best-corrected visual acuity of 20/200 or worse, or a visual field of 20 degrees or less, is defined as legally blind.
• Functional blindness--the absence of any usable vision. Only about 1 in 10 visually impaired people are functionally blind. Most have some usable vision.
• Low vision or visually impaired--term used to describe people with significant vision loss that can not be corrected medically or surgically. These vision problems impact work, school, recreation and other activities of daily living. People who are partially sighted and/or legally blind are often described using these terms.

Eye Diseases

• Cataracts--a clouding of the eye's lens that diminishes vision.
• Diabetic retinopathy--small blood vessels that nourish the eye's light-sensitive retina weaken and change. Visual symptoms depend on where the blood vessel changes are taking place in your eye's retina.
• Glaucoma--fluid that does not properly drain causes pressure within the eye that can damage the optic nerve and lead to vision loss. Glaucoma affects side vision before central vision is affected.
• Macular Degeneration--damage to the part of the retina (back of the eye) responsible for central vision and the ability to see detail. The dry form is caused by the thinning of the tissues of the Macula; the wet form occurs when abnormal blood vessels at the back of the eye hemorrhage.
• Optic atrophy--degeneration of the optic nerve, the fibers that transmit electrical information from the retina to the brain where it is translated into vision that leads to loss of clarity or changes in the field of vision, or both.
• Retinitis pigmentosa--a hereditary eye disorder causing gradual destruction of the retina. Sight loss is usually gradual but progressive.

Vision Care Professionals

• Ophthalmologist--a medical doctor trained in vision and eye diseases that is licensed to perform surgery on the eye. Individuals with serious vision problems need to see their ophthalmologist regularly to insure their condition does not become more severe.
• Optometrist--trained in vision and eye diseases and can prescribe corrective lenses and diagnose eye diseases, but does not perform surgery.
• Optician--a technician who makes and fits corrective lenses.

Rehabilitation Terms

• Functional low vision exam--an exam by a low vision specialist that determines the extent of a person's remaining sight. Presently, fewer than 5% of all eye doctors specialize in low vision.
• Vision rehabilitation--tools and training to help people with significant vision loss maintain their independence. The vision loss is permanent but the ability to perform daily living tasks with impaired sight is learned or relearned in vision rehabilitation.
• Adaptive or assistive technology--term used for technology that uses magnification, contrast, synthesized speech, and/or lighting to maximize a person's remaining sight.
• Optical low vision aids--prescribed optical devices such as Bioptic glasses, often specially created by the doctor to help reach a person's visual goals, or electronic devices, such as the closed circuit television (CCTV), scanners and computer software.
• Non-optical low vision aids--items designed to promote independent living, such as talking calculators, talking alarm clocks and watches, signature or check writing guides, large print checks and calendars.
• Independent living skills--training in adaptive techniques for cooking, grooming, labeling and money management can increase independence. Instruction takes place in the home or in a structured classroom setting.
• Orientation and mobility training--training in safe and independent travel skills around your home or your neighborhood.

The previous info was modified from the original form at www.low-vision.org.