Some people cannot see the things they need to see even though they are not blind. Their problem is low vision.
Low vision refers to impaired vision that does not improve through medicine, surgery, or ordinary corrective lenses. Individuals with low vision find it difficult or impossible to do many everyday tasks. For example, they may be able to walk unaided but may not be able to see someone’s face.
What are the symptoms of low vision?
Low vision is not blindness, which is the absence of useful vision or light perception. Persons with low vision may see light, color, movement, dimension, shape and size. However, things can appear blurred, faded or distorted. Objects may seem to be “jumping about” “not all there” or “not there at all.”
A person’s visual acuity-the ability to see fine detail-can worsen. There can be a narrowing or loss of parts of the visual field-the area of sight. Someone with low vision may be less sensitive to differences and changes in brightness, contrast and color. Adaptation to high or low levels of light may be slowed or impossible. Various combinations of these changes in vision can occur.
How many people have low vision?
Nearly 2 million people are severely visually impaired and cannot read ordinary newsprint even with reading glasses, according to projections based on 1986 data from the National Center for Health Statistics. Another 6 to 9 million people have impaired vision that may interfere with their ability to perform some activities.
About 77 percent of severely visually impaired people are at least 65 years of age. Many of these persons have other physical problems; low vision often can be the crucial factor that prevents them from living independently.
What causes low vision?
Age-related eye diseases, eye injury or other eye diseases may disrupt normal visual function and result in low vision. Visual complaints differ depending on which part of the visual system is damaged. Inability to do an activity depends on whether the problem affects side vision, central vision, brightness, color, or contrast.
Distortion or loss of central vision can occur in age-related macular degeneration: the leading cause of new cases of legal blindness in people 65 and older. In this disease, there is a progressive breakdown of the macula: the central part of the retina that permits the greatest perception of detail and color. Activities requiring good central vision, such as reading, sewing or driving, are difficult for persons with this disease. On the other hand, since macular degeneration does not affect side vision, walking in familiar areas often poses few problems.
Other eye conditions also may cause low vision. These include retinal diseases such as diabetic retinopathy and retinitis pigmentosa, glaucoma, cataracts, scarring of the cornea and retinal detachment.
What can help low vision?
Although low vision means a loss of vision, it also means that some vision remains. Low vision rehabilitation tries to make the best use of any residual vision, to reduce the handicapping effect of the visual impairment. Achieving this goal is possible in most cases.
To help in this task, there is the low vision specialist – an optometrist, ophthalmologist or professional trained in low vision rehabilitation. The low vision specialist assesses a person’s visual abilities and vision-related needs. Together they explore ways to improve the individual’s performance in daily activities. These options include:
- Magnification. Optical aids that enlarge objects are hand and stand magnifiers, reading glasses, binoculars and telescopes. Non-optical devices such as large-print books, closed-circuit TV reading machines, and print-enlargement computer software can also be helpful.
- Illumination. Devices that control the effects of light, contrast and glare include: sunglasses, visors, adjustable lighting, flashlights, and illuminated magnifiers. A practical example is marking the edge of steps to improve visibility.
- Viewing techniques. Eccentric viewing (looking to the side of an object instead of directly at it) is an example of an adapted viewing technique. This can be useful for persons with central vision loss.
- Non-optical devices. These types of items make visual tasks easier by improving viewing conditions. Examples include: large-print playing cards, writing guides, reading stands, and black felt-tip markers.
- Non-visual devices and adaptive techniques. Senses other than vision are used to perform daily activities. Examples of non-visual devices: Talking Books, radio information services, optical character readers, tape recorders, talking wristwatches and calculators, folding and support canes, and tactile markings to identify objects by touch.
- Task or environment modifications. Individuals can change how or where they do an activity, for example, moving a TV to avoid reflections from nearby windows.
- Other consultations. The effect of low vision on a person’s quality of life is not strictly visual. Often, a solution to a low vision problem may require discussion with family members or consultation with other professionals. These may include teachers, social workers, physical therapists, vocational or recreational counselors and orientation and mobility instructors (specialists in travel techniques for blind or visually impaired persons).
Good low vision care includes instruction and encouragement in the use of recommended devices and techniques. Follow-up care also is important. The rehabilitation program may need to be revised if persons with low vision have further changes in vision or in what they need to do.
Loss of vision affects each person in unique and profound ways. No one low vision aid can solve all the problems that a visual impairment causes. However, the combination of low vision devices, techniques, services and resources has the potential to greatly help a visually impaired person.