Functional Vision Screening for Severely Handicapped Children
Beth Langley, M.A., and Rebecca F. DuBose, Ph.D.
Abstract:
Ophthalmologists traditionally have been unable to provide teachers and parents with useful information about a severely handicapped child's functional vision. Literature concerning the assessment of vision in handicapped children is reviewed and a guide is proposed for use by teachers in evaluating the severely handicapped child's functional vision.
Severely handicapped children with some form of visual impairment are often placed in educational settings accompanied by inadequate reports giving some indication of visual classification and an unintelligible description of the specific impairment. References are repeatedly made to the difficulties involved in assessing the child's visual problems and to the hesitancy with which the ophthalmologist makes his judgment. In centers where a multidisciplinary team evaluates the child, vision experts tend to rely on the functional visual information provided by the classroom teacher or the educational diagnostician. A more practical assessment of visual functioning in severely handicapped children will therefore become available if those agents most familiar with the child's everyday use of vision actually participate in the assessment.
This paper describes some of the difficulties found in testing the visual acuity of severely handicapped children, surveys formal and informal measures used in testing visual acuity or functional vision, suggests guidelines for teachers to use in observing visual behaviors, and proposes a functional vision checklist that may be used by teachers or paraprofessionals to gain insight into how a child is using his residual vision (see
Box 1).
Formal assessment of visual acuity
The problems inherent in determining visual acuity of multiply handicapped children have been stated by Allen (1957), Wolfe and Harvey (1959), Hoyt (1963), Sloan and Savitz (1963), Ffooks (1965), Borg and Sundmark (1967), Faye (1968), Lippman (1969), Macht (1971), and Sheridan (1973). Under the conditions imposed by the instruments used for testing visual acuity, low functioning children are easily distracted, lose interest in the test, fear the testing situation, fail to understand the tests, and give unreliable and inconsistent responses. Special educators and ophthalmologists have tried to find visual acuity tests that are effective with severely handicapped children, since visual impairment is frequently found with other handicapping conditions. Blackhurst and Radke (1968) found that moderately retarded children had four times as many visual impairments as the normal school population; Vernon (1969) reported that approximately 25 percent of deaf children had some form of visual impairment, and Wolf and Anderson (1973) provided evidence of visual limitations in 50 percent of cerebral palsied children.
What is visual acuity?
Wolfe and Harvey (1959) defined visual acuity as the ability to distinguish small spatial separations, or intervals, between portions of the visual field. Since it depends upon the ability of the eye to resolve a given visual angle, acuity is greater the closer together are two points that can be distinguished. Wolfe and Harvey distinguished sensory from visual acuity as an individual's reaction to low-keyed sensory data of mild duration and extent. Lippman (1969) suggested that sensory impressions developmentally advance from discriminative and perceptual stages to a conceptual stage.
Sheridan (1970) segmented acuity into two separate processes which are particularly relevant to multiply handicapped children: seeing and looking. Described as a physiological process dependent upon intact visual mechanisms, seeing is "the reception of mobile and static patterns of light, shade, and hue by the eye and transmission of this information to the central nervous system" (Sheridan, 1973). Primarily a psychological process, looking combines perceptual and conceptual operations to attend to visual stimuli with purposeful interpretation of their meaning.
As the child's awareness of his world increases so does his ability to distinguish visually and to respond to more abstract forms of stimuli through gradual refinement of his acuity to its mature state. Sheridan (1973) believes that by 12 months a child has a visual acuity comparable to adult vision, although it is not efficiently developed. A child of kindergarten age should be able to attend to an object for at least 20 seconds, pursue a moving target in all directions with a minimum of head movement, and localize different visual stimuli within the environment (Banus, 1971).
The majority of multiply handicapped children with significant visual deficiencies retain some functional vision and do see. However, their limited experiential and cognitive repertoires-essential to the integration of sensation into meaningful stimuli-prevent them from looking.
Formal tests and procedures
The formal tests that offer the most promising information about the extent of visual functioning of multiply handicapped children are Sheridan's Stycar Vision Tests and Koehler's New York Flashcard Vision Test (Faye, 1968). These tests were developed specifically for use with handicapped children and to assess near as well as distant vision.
Lippman (1969) found the Stycar to be the most reliable test in screening visual acuity of preschool children. Although Sheridan devised a distant screening chart consisting of only nine capital block letters chosen on the basis of simple vertical and horizontal lines (L H T), the circle (O), the cross (X), the part-square (U), the triangle (A), and the part-triangle (V), her Miniature Toys Test and Rolling Balls Test (subtests in the Stycar battery) are in fact more useful for evaluating vision in multiply handicapped children.
The Miniature Toys Test was developed for use with severely handicapped children who were unable either to match letters or name and match colored pictures of common objects placed individually on cards. After experimenting with numerous toys, Sheridan found the most effective ones to be a car, plane, doll, chair, knife, fork, and spoon, all 2 inches high; a larger knife and spoon 3 1/4 inches high; and a doll 5 inches high. She found that children as young as 21 months successfully matched the objects and that their interest in the task lasted for its duration.
Designed particularly for use with children from six to 30 months, the Rolling Balls Test consists of a series of graded balls projected a distance of 20 feet. The child is required to retrieve them one by one after they have been rolled horizontally across his line of vision.
The New York Flashcard Vision Test was developed out of a need for assessing the visual acuity of multiply handicapped children, visually handicapped preschool children, and the nonreader of any age (Faye, 1968). Only three symbols (heart, house, and umbrella) make up the test. They are presented one at a time on 12 reversible 4-inch by 5-inch flashcards. Snellen acuity notation is printed on every card, three symbols for each acuity level from "200" characters to "10." As long as they are consistent, children may verbally or manually label symbols anything they like or, if unable to express themselves, can point to large matching symbols. Average children of 27 months consistently attended and responded appropriately to the three symbols, and Faye successfully screened trainable mentally retarded children with the cards. The test is administered to the conventional method of acuity testing, except that the test distance is ten feet or less and notations can be converted to the 20-foot reading.
Unsuitable tests
Other formal measures of visual acuity have required skills not in the repertoire of multiply handicapped children. Sloan and Savitz (1963) identified two major forms of visual acuity tests, those based on indicating directions and those requiring identification of pictures.
In reviewing tests based on indicating directions, Sheridan (1973) felt that the Snellen E, the Sjorgen-Hand Test, and Landolt's Broken Rings included three major factors that significantly influenced the low functioning child's ability to perform adequately on them. Because multiply handicapped, as well as preschool children, have difficulty in coping with diagonals, they responded only to figures pointing up, down, left, or right. Directionality also complicates the assessment of multiply handicapped children as they confuse left and right and, although they may perceive laterality, they experience confusion in duplicating the position of the symbols. Because the patterns presented are constant, no opportunity is available to observe the child's ability to discriminate differences in configuration (Sheridan, 1973 and Ffooks, 1965).
Picture identification tests have been most frequently employed in testing handicapped populations though numerous adapted procedures have been necessary. Osterberg (1965) specified three requirements to bear in mind in the selection and development of pictorial visual acuity charts: 1) optometric principles must be adhered to as closely as possible; 2) objects must belong to the child's world of ideas; and 3) presentations of pictures must be adapted to the child's demands for recognition of pictures greatly variant from adults' needs. Other authors (Allen, 1957; Wolfe & Harvey, 1959; Hoyt, 1963; Faye, 1968; and Sheridan, 1973) have stressed the importance of using pictures of objects within the child's experiential repertoire. General criticisms of picture charts were that the pictures inaccurately projected angles at a nodal point corresponding to the highly accepted Snellen E symbol and required personal experience and ability to recall labels. More specific concerns have been expressed by Sloan and Savitz (1963), Borg and Sundmark (1967), and Ffooks (1965). Sloan and Savitz (1963) and Ffooks (1965) stated that picture tests were too dependent on psychological interpretations of figures before they could be understood and recognized by children.
Informal testing of visual acuity
Adaptations of formal tests have included deleting items; projecting them onto large screens; manipulating three dimensional response materials; converting response forms into puzzles; altering the type of figure, outline, silhouette, background, or color of the target and response figure; and applying operant technology (Courtney & Heath, 1971 and Macht, 1971). Although numerous tests have been developed and adapted with handicapped children in mind, none have proved satisfactory for use with this population unless administered through some form of operant procedure.
Employing an operant approach, Courtney and Heath (1971) trained and evaluated color vision in 39 trainable and 71 educable mentally retarded children using the AO HRR Color Vision Tester to determine the percentage of color blindness among the population of mentally retarded individuals. They found the AO HRR effective, as it offered four training and six testing plates graded for both type and severity of color blindness. The test proved to be highly motivating, required no verbal responses, no ability to read conventional numbers, and no need for the coordination essential for tracing paths. Training the children to take the color form of the test was accomplished through a black and white adaptation of the colored symbols O, X, and Delta. Identical forms were painted on slabs hinged to a box which dispensed M & M's whenever a correct response was given. Most children required about five minutes of training, but the authors succeeded in testing one 12-year-old Mongoloid child with an IQ of 35 after 40 minutes of training. No difference was found in the prevalence of color blindness among mentally retarded individuals and that of normal individuals reported in the literature.
Macht (1971) applied operant technology to obtain a subjective measure of visual acuity in five mentally retarded children between five and seven years of age. He included in his subject population two adults of normal intellectual and visual functioning to verify his results. Through the use of a specially constructed wheel displaying two stimulus Snellen Illiterate E's, one at the top and the other at the bottom of the wheel, and a table containing a response mechanism, Macht not only devised a way to evoke responses to the Snellen Illiterate E Chart, but also included an elaborate training system. The children were placed at the table 20 feet from the wheel and were trained to respond by pushing the response lever to the upright E, as opposed to the E which inverted as the wheel turned. Subjects were reinforced with M & M's and small candies for appropriate responses. The initial training E was larger than the 20/200, but for the actual testing the 20/200, 20/100, 20/70, 20/50, 20/40, 20/30, and 20/20 E's were utilized. Obtaining significant successful results that correlated with the adults' responses, Macht attributed children's previous failures to respond to the Snellen E and other visual acuity tests to procedural inadequacies rather than to the presence or absence of some quality in the child himself.
Macht and Courtney, with their promising results, offered the field of visual assessment valuable implications for successful application of tests that had previously proved ineffective with multiply handicapped children. Teachers cognizant of how children functionally use their vision can give ophthalmologists information that is helpful in determining visual capacities. Assessing functional vision in the severely handicapped child is a first step in planning educational programs relevant to his needs.
Informal teacher-oriented visual screening
Informal teacher-oriented visual screening procedures can effectively obtain important, practical information regarding what a child sees and how well he sees it. Although informal, the evaluation should be carried out systematically. Establishing a working rapport with the child, the setting, and stimulus materials is of primary importance. With a particularly young child, it may be necessary to hold and rock or sing to him for several minutes to quiet him. Sharing a manipulative toy often helps the evaluator to gain the confidence of an older child. The setting should be small, uncluttered, and quiet. Working with the child on the floor, where the evaluator has easy access to both the child and materials, facilitates administration of stimulus materials, puts the child and evaluator on the same level, and prevents attempts to leave a table, slip from a chair, or push materials from the table. Multiply handicapped children are more responsive to highly motivating materials, although in this assessment they must be limited in sound components to insure that the child is attending visually rather than aurally.
Suggested materials for eliciting visual behaviors outlined in the checklist are brightly colored soft rubber squeak toys with the squeaker removed (this toy can be squeezed to produce action but the sound is eliminated), a penlight or small flashlight, fluorescent rubber toys containing lights, and mechanical toys having flints producing sparks when operated. Especially motivating for severely handicapped children are rattles encasing moving parts; large and small spinning tops and easily rolled cars; fluorescently colored inch cubed blocks; small candies or cereals such as M & M's, Froot Loops, cake decorating items; and roly poly action toys. Other suggested materials are a small box, paper and brightly colored magic markers; plastic pegs and board; brightly colored, textured books with thick pages; large beads; stacking cones; a primary puzzle with approximately three pieces; multicolored counting bears; shape sorting chips or parquetry blocks; simple pictures in duplicate glued to small index cards; or commercially produced pictures and duplicates of different colored toys for matching.
The first stage of the visual assessment should be to observe the child for immediately obvious visual abnormalities and behaviors indicating deficient vision. Primary questions to be answered should focus on the presence or absence of basic visual responses, and the types of visual stimuli (light, movement, color) to which the child attends. Observing not only the manner and direction in which the child reacts to visual stimuli, but also the distance and size of objects eliciting the most consistent response, provides insight into the positioning of specific materials useful in obtaining maximum visual attention. Equally important is the assessment of the child's ability to integrate visual stimuli with cognitive and motor processing skills to perform discrimination, association, figure-ground, and eye-hand coordination activities. Simple techniques for use in assessing five aspects of visual function are given below. Figures I through V suggest check lists a teacher may use for recording information about a multiply handicapped child's performance.
Techniques for functional vision screening
I. Presence and nature of the visual response
a. Direct a penlight into the child's eyes from 12 inches away and observe whether the pupils constrict, then dilate when the light is removed. Be sure to observe his eyes before shining the light as blind children often exhibit hippus, a continual constricting and dilating of the pupil.
b. Assessing a tendency of the eyes to deviate can be done by flashing a beam from a penlight into the child's eyes from 30 inches away. If the light is reflected simultaneously in the middle of each pupil, no deviation is present. If the reflection is centered on one pupil but off-center in the other, some form of muscle imbalance is indicated.
c. Place the child on his back and kneel behind his head. Pass your hand across his eyes, pause and repeat. A blinking reflex indicates some light perception and possibly some object perception.
d. Assess the child's perception of light using a penlight. From 12 inches or closer flash the light and note whether he attends to it. The light should be flashed slightly above, below, to the left, and right of the child's face to determine the range of visual field. Note whether he fails to attend to the light in any plane.
e. Sitting behind the child, bring the light slowly into his right, then his left visual field. Note at which point he turns to look at the light. He should notice it when it is directly in line with the lateral portion of the eye.
f. Present the child with play objects of equal interest simultaneously in the right and left visual fields and gesture for him to touch them, switch their positions and repeat. Observe whether the child attends to a toy in only one position rather than both.
g. While holding a motivating toy 12 inches to 18 inches in front of the child's eyes, alternately cover each eye. Observe whether he resists having one or both eyes covered or if he remains indifferent to the covering. Children having limited or no vision in an eye will not mind having that eye covered but will strongly resist covering of the functional eye.
II. Reaction to visual stimuli
a. Observe the child for any inappropriate visual behaviors such as light flicking with fingers or objects or eye poking.
b. Evaluate the child's ability to localize, track, and scan by holding puppets, small squeeze toys, or penlights within the child's range of vision. Move them slowly from left to right, up and down, and in oblique angles. Note whether he locates an object efficiently and attends for at least 20 seconds.
c. Place toys at all levels and in all directions and watch to see if he turns and reaches for them. These items should be interspersed throughout the evaluation to maintain interest in looking.
d. Note whether the child is able to shift his attention by holding two toys of equal interest approximately one foot apart in front of the child. Shake one, pause, then shake the other. Observe whether he shifts his gaze to the other toy.
e. Observe his ability to scan by placing three objects in front of him and watch to see if he shifts his attention from one toy to the next in line.
III. Distance and size of objects and pictures
a. While interacting with the child, scatter small pegs or candies 1/4 inch in diameter, inch cubed blocks, counting bears, or shape chips around the child and encourage him to find them. Note the distance at which he most consistently attends to the various sized objects.
b. Project large (6 inch to 8 inch in diameter) and small (2 inch to 3 inch in diameter) toys to the left, right, and forward from the child and observe how far they travel before he looks away or ceases in his efforts to retrieve them.
c. Using a set of toys that duplicate, except for color, those used in B, have the child match his objects with yours as you display them singly. Begin at 10 feet for large and 5 feet for small objects. Obtain the maximum distance at which the child sees the objects without straining by moving backwards or forwards in 2-foot intervals until he consistently matches four or five objects.
IV. Integration of visual and cognitive processing
a. Tap or pour blocks and pellets from containers in front of the child. Note whether he looks at them as they tumble before him.
b. Scribble large circular motions with magic marker on white paper in front of the child. Note whether he watches or attempts to take the marker.
c. Give the child M & M's to hold, help him place them in a small box and shake them around. Take the box from the child and quickly remove the candies. Watch to see if he looks for the candies when you return the box.
d. Give him a large colorful book to look at. Note whether he bends to look at the pictures or pats them.
e. Give the child a toy which has continuous action and attracts his attention. As he watches, push the toy out of his sight and note if he looks for the toy. Replace it before him without the motion and observe whether he attempts to reactivate it.
V. Integration of visual and motor processing
a. On activities involving the pegs, stacking cone, puzzles, pounding bench, and beads, watch to see if he directly inserts or applies pieces, overreaches (O), or underreaches (U). Does he look for the recess and the hole or does he only tactually approach them?
b. When shown one colored block, shape, or 2-inch picture at a time, can he match it, given only two choices? Watch to see which colors, shapes, and pictures he matches and if he attends to color or configuration. Observe the distance from the materials at which he works, then have him match them at a far distance. Note the farthest distance at which he correctly matches each.
Summary
Traditional tests of visual functioning and acuity have lacked the impetus essential for assessing children with multiple impairments. Although operant measures have been successful in eliciting behaviors required to respond to these tests, Sheridan and Koehler have offered the most promising formal tests for this population. Until the use of the New York Flashcard Vision Test and the Stycar Vision Test is more widespread, the task of visual assessment remains primarily with the teacher. Obtaining even a gross indication of the child's functional visual field-a preferred eye, distance at which he most efficiently works with various sized objects, and the level of complexity of the visual stimuli that the child successfully interprets-provides the teacher with basic information needed to design an educational program relevant to the child's visual and developmental needs.
References
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Banus, B. S. The developmental therapist. Thorofare, N.J.: Charles B. Slack. Inc., 1971.
Blackhurst, B. & Radke, E. Vision screening procedures used with mentally retarded children-A second report. Sight Saving Review, 1968, 38, 84-88.
Borg, C. & Sundmark, U. A comparative study of visual acuity tests for children. Acta Ophthalologica, 1967, 45, 105-113.
Courtney, C. R. & Heath, G. G. Color vision deficiency in the mentally retarded: Prevalence and a method of evaluation. American Journal of Mental Deficiency, 1971, 76, 48-52.
Faye, E. E. A new visual acuity test for partially-sighted non-readers. Journal of Pediatric Ophthalmology, 1968, 5, 210-212.
Ffooks, O. Vision test for children: Use of symbols. British Journal of Ophthalmology, 1965, 49, 312-314.
Gorman, J. J., Cogan, D. G. & Gellis, S. S. An apparatus for grading the visual acuity of infants on the basis of optokinetic nystagnmus. Pediatrics, 1957, 19, 1088-1092.
Hoyt, W. F. Neuro-opthalmologic examination of infants and children. International Ophthalmology Clinics, 1963, 3, 757-775.
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Macht, J. Operant measurement of subjective visual acuity in non-verbal children. Journal of Applied Behavior Analysis, 1971, 4, 23-296.
Osterberg, G. A Danish pictorial sight-test chart. American Journal of Ophthalmology, 1965, 59, 1120-1123.
Sheridan, M. D. Manual for the Stycar Vision Tests. Windsor, Ontario: NFER Publishing Company, Ltd., 1973.
Sloan, A. E. & Savitz, R. A. Vision screening. International Ophthalmology Clinics, 1963, 3, 815-831.
Vernon, M. Multiply handicapped deaf children: Medical, educational, and psychological considerations. Washington, D.C.: Council for Exceptional Children Monograph, 1969.
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Wolfe, W. & Harvey, J. The evaluation and development of techniques for testing the visual and auditory acuity of TMR children. Eric document 002 802. Austin, Tx.: College of Education, Texas University, 1959.
Ms. Langley is educational diagnostician and Dr. DuBose is associate professor, Faculty of Special Education, Model Vision Project, George Peabody College for Teachers, Nashville, Tennessee.
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