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by Carol Evans [

A school psychologist asked a question about testing of students with blindness and visual impairment.

QUESTION: I am interested in the intellectual assessment of Blind and Visually Impaired students. Many of the measures normed on this population are quite dated.

What is the current state of "Best Practice" in the assessment of this population?

A Teacher

RESPONSE: Dear Teacher, 

You are correct in stating that many of the tests geared for the blind are old. They also have a number of other limitations, both technical and practical. The Perkins-Binet has been withdrawn from the market and is no longer considered ethical to use. It may be interesting for you to know that the P-B used miniatures for object identification.

This is inadequate because miniatures do not represent real items to a blind child in the same way that pictures represent them to a sighted child. The Blind Learning Aptitude Test (BLAT) was a noble pioneering effort by T. Ernest Newland in 1969. It can still be obtained, but the norms are 30 years old, quite inflated for today's examinees. The printing currently being sold by the publisher has errors in two items which with the help of Alan Koenig, who had an older, more accurate version, and a tactile graphics kit, I was able to fix on my copy. I sometimes use it for qualitative purposes to describe how a blind student approaches a tactile task. I do not report scores. I hope that a revision of this test will be published some day, as did the late Dr. Newland. It needs better (more durable) materials (it is embossed on paper, and wears down after a few uses. It also needs improved layout and better spacing of stimuli and response items.

The Bartimeus Center in Holland has published a test for the blind called the Intelligence Test for Visually Impaired Children. It is said to be based on Thurstone's theory. Standardized on the entire Dutch-speaking braille-reading population of Holland and Belgium (about 156 children) It has both verbal and tactile performance subtests, and is published in Dutch, German and English. There are only a few in this country, and there have not, to my knowledge, been any studies published yet on English speaking children. The school for the blind for which I work is ordering the test now (it is quite expensive), and I may do some doctoral research with it. Opinions are divided among those who have used it. (Some swear by it; some swear at it!)

As far as best practice is concerned, if children are blind (little or no useful vision, learning tactilely), many school psychologists are using the Wechsler Verbal Scale; some also qualitatively describe non-verbal ability by observing braille reading, and other manipulative tasks.

Some psychologists give only the Verbal Scales to children with low vision, even those who are using print for learning. I believe that this practice leaves out an important component of the assessment: how effectively, and how efficiently, does the child use vision?

This question may be answered in part by using the entire Wechsler scales, reporting only the verbal score, and describing the child's approach to, and success with visual-spatial tasks for qualitative purposes only. The purpose of this procedure is to illustrate the ways in which performance degrades when excessive demands are made on a faulty visual system (Richard Russo, School Psychologist, California School for the Blind).

It is incorrect to compute a Performance IQ and Full Scale IQ for these children, as scaled scores have been shown to vary with visual acuity (particularly on timed tasks, and especially on those with bonus points for rapid completion).

Prior to testing, obtain information about the etiology and characteristics of the vision loss, severity, age of onset, and other aspects of the child's medical history. Is it an ocular problem only? Or is the vision loss part of a larger syndrome, with other possible learning and behavior implications? Is it static or progressive? Is hearing normal or impaired? This last is a very important consideration.

You may obtain important information about the child's visual function through consultation with the certified teacher of the visually impaired, who should have performed a functional vision assessment. In some cases the child may have had such an evaluation by a low vision therapist at a school for the blind, or some other blindness agency. If no such report is available, you will want to make your own observations of how vision is being used in classroom tasks prior to testing. Any and all adaptations used by the student for print enhancement in the classroom are appropriate when testing.

The psychologist is encouraged to "interpret with caution" when writing the report, and to explicitly say so, for two reasons:

  1. Some items, even on the verbal scales, have been shown to be biased against children who have very severe, early (congenital or soon after) loss of vision.
  2. You will be using accommodations for access to the materials, which should be explicitly described in the report.

A substantial body of prior research with the Revised versions of the Wechsler scales showed a tendency to lower Comprehension (and on some studies, Similarities and Information) scores. It also pretty consistently showed higher scores on Digit Span (regarded as a compensatory skill).

Those with whom I have communicated in the recent past, who work with this population, say that these tendencies to such profiles are still being expressed in many cases with the Third Editions of the WISC and WAIS, although I have been unable to find any published studies replicating those earlier results with these updated tests.

Carol Anne Evans, M.Ed.