Visual Impairment

There are legal and educational definitions of visual impairment (VI). Visual acuity, the ability to see objects clearly and to distinguish details at a specific distance, is the criteria used to decide whether an individual is legally blind. Acuity is measured by reading letters or symbols from a chart at a distance of 20 feet. If a person needs to stand at a distance of 20 feet to see what most people see at 70 feet, that person has 20/70 vision.

A person is considered legally blind if they have visual acuity of 20/200 or less in the better eye, with glasses or corrective lenses. A normal field of vision is 180 degrees. A person may also be considered legally blind if their field of vision is limited to 20 degrees or less.

The educational definition of VI is contained in Arizona Revised Statutes §15-761(37), which states: " 'Visual impairment' means a visual impairment . . . that interferes with the child's performance in the educational environment and that requires the provision of special education and related services."

Besides impairments to visual acuity and to the field of vision, there are other ways in which vision is affected. The ability of the eye to move (ocular motility) and the ability to merge two separate images into one (binocular vision) can affect a child's vision. Strabismus, the inability to direct the eyes to the same object, may sometimes result in amblyopia. Amblyopia, also known as "lazy eye," frequently results in a reduction or loss of vision in the weaker eye.

Other types of visual impairment include far-focus/near -focus vision problems and nystagmus. A child may not be able to switch easily from far-focus to near-focus vision. For example, it may be very difficult or impossible for a child to copy from the chalkboard (far-focus) to a paper on his/her desk (near-focus). Nystagmus involves rapid and involuntary movements of the eye. It can cause difficulty in focusing the eyes and tracking a line of print in a book, creating reading problems.

How Common Are Visual Impairments?
In the 1997-98 school year, 645 students in Arizona were eligible for special education services as a result of visual impairments. This number represents .081 per- cent of the 794,928 children enrolled in Arizona public schools as of October 1, 1997.

What Effect Do Visual Impairments Have on a Child?
Each child with a visual impairment is unique. Two children with the same impairment may have different ways of adjusting to a particular disability. Orientation/ mobility training has been found to be helpful to most visually impaired students. The training assists students in learning about their environment so they may move about safely.

It is important to discover the method that a student with a visual impairment uses to learn. The age of the child at the time the visual impairment is discovered needs to be considered in planning an educational program. Children who are blind from birth sometimes need different techniques and accommodations than do students who were sighted and lost their vision due to an illness or an accident.

Many children can be helped through assistive technology such as braillewriters, talking calculators, tape recorders, telescopic aids, magnifiers, tinted lenses, overlays, and other optical aids. Through the use of the Optacon (Optical to Tactile Converter), many blind children are able to read regular print. A closed-circuit television system which enlarges standard print allows students with low vision to use regular textbooks. The Xerox (Kurzweil) Reading Machine is another helpful device for students with visual impairments. It reads books aloud in different voices and at varying rates of speed. Depending on the vision available to a child, Braille or large type print material may be appropriate. The unique needs of each child should guide what aids and materials are used.