«Physician’ Visual Rating System Instruction Manual A significant aid to the detection of vision problems as they affect perception, child ...»
Visual Rating System
A significant aid to the
detection of vision problems
as they affect perception,
child development, and
No skill is so important to individual as the skill of vision. It gives him/her control over his/her
relation to his/her space world. According to the late Dr. Arnold Gesell, founder of the Gesell Institute of
Child Development, “Vision is the dominant factor in human development.” The consideration of vision as a factor of both health and behavior is, therefore, well within the purview of the psychologist, the pediatrician, and the physician in family, industrial, or public health practice…as well as the ophthalmologist and optometrist.
Visual efficiency Vision-the complete act of seeing and integrating/interpreting what is seen-is an ability that develops as the individual develops. Dr. Gesell put is simply: “Vision,” he said, “is learned.” As a result, visual efficiency is only partially dependent on the health of the component tissues and the refractive status of the eyes. Of equal or greater significance is the ability of the individual to adequately develop eye teaming, eye-movement, and related elemental skills.
This means that even in the absence of pathology or refractive disorders, a problem of vision may exist. And visual problems, just as vision itself, are acquired. Studies at the University of Chicago Hospital indicates that only 2%-2 ½ % of infants have organically defective eyes. Yet it has been reliably estimated that at least 40% of the U.S. population is handicapped by some visual dysfunction.
The examination of vision Because the entire organism is at some point involved in the visual act, vision problems cannot be considered as existing in isolation. The visual mechanism, therefore, cannot be effectively examined as if it was a fixed system. Neither the eye nor the associated neuromuscular tissues are static in nature.
To be significant, any examination of a patient’s vision should include various tests of functional skills as well as a search for pathology and a determination of end-organ defects (refractive problems).
These functional factors are considered essential: Ocular motility, fixations, accommodative ability, convergence skill, binocularity, fusion, stereopsis, and the eyes’ relative posture. A check for suppression should also be made, and a survey of color discrimination is desirable.
Eye movement, fixations, accommodation, and convergence may be simply tested using only a pencil or penlight for the patient to follow. The other tests, however, require more sophisticated instrumentation…although they need not be either elaborate or time-consuming. This is why the Keystone Vision Screening Test Set was developed.
Keystone visual skills screening The visual mechanism can be most accurately measured when it is acting in response to normal environmental demands. For this reason, the Keystone test set optically approximates those conditions of seeing normally faced in daily living.
It checks key visual skills, including acuity. It determines if suppression exists and gives some indicators of refractive problems. (Supplemental test materials are available for the evaluation of farsightedness and astigmatism.) Unlike wall-chart testing, Keystone tests are binocular, requiring the two eyes to work together.
All tests are conducted with both eyes open and seeing, even when only one eye is being checked.
Thus, any cases of suppression and/or imbalance-often undetected by conventional methods when one eye is occluded-are more easily determined.
In addition, many of the stereo test targets have three-dimensional properties. By correctly locating objects in the targets, the patient demonstrate his/her total skill in judging spatial relationships.
General test procedure Keystone vision screening tests are easy to administer. The test subject is seated in front of a Telebinocular® test instrument. He/she looks into the instrument and views a series of stereroscopic test target slides. The examiner explains each target and the subject reports what he/she sees. His/her responses are checked on a record form.
Testing is rapid…and it’s enjoyable for all ages. Children, in particular, appreciate being given a fair chance to demonstrate their visual performance.
Near-point and far-point information Keystone screening tests measure visual skills at both far point and near point. Far point, often indicated by the symbol “∞”, is the equivalent of an actual distance of six meters (approximately 20 feet).
Near point is the equivalent of 40 centimeter (about 16 inches) and is the normal working/reading distance.
The Telebinocular produces both distances optically by means of lenses and precision-scaled target slides. This not only conserves space, but also makes Keystone tests particularly valuable in checking the vision of person who must make a heavy demand on their eyes in reading at near point.
Test significance and accuracy Please bear in mind that the Keystone tests are designed for rapid screening purposes only: To determine the possible need for a professional analytical examination. They are not intended to provide detailed diagnostic data…and should not be compared test-by-test with clinical findings obtained in an ophthalmologist or optometrist’s office.
Yet the tests are accurate and dependable. All are objective and psychologically sound, and all are given under standardized conditions. Overall results show very high validity. In fact, the tests are so reliable that thousands of vision specialists use them to assist in diagnosis.
The Keystone Telebinocular is the accepted pioneer of modern binocular vision testing instruments. Completely self-contained, it is designed for simplicity of use. Because it weighs less than fourteen pounds, it can be easily carried to any convenient test location. And it requires only one square foot of desk or table area wherever it is used.
1. Carrying handle-makes moving the Telebinocular easy. Retracts into the viewing head when not in use.
2. Headrest-tester’s forehead should rest lightly against this strip. Disposable tissue headrest cushions are available as an accessory.
3. Professional-quality lens system-Achromatic prism lenses are accurately postioned for use by anyone without adjustment.
4. Occluders- Permit testing one eye at a time to check the possibility of visual suppression.
5. Viewing head
6. Support arm
8. Light-Lamp at top of viewing head provides even, non-glare illumination of targets. Uses readily available, standard-type bulbs.
9. Cardholder-Accommodates twenty test targets, locks in place to prevent slippage during testing.
Open design allows use of a pointer from the top or the sides.
10/11. Test distance pre-calibrated-Far point (equal to 20 ft.) and near point (equal to 16 in.) are produced precisely by optical means. To establish distance, move holder to near or far stops on twin shaft.
12. Locking knob-Prevents movement of viewing head during tests. Height of head is easily adjustable for each tester through a 6-¼ inch range.
How and why the occluders are used The Telebinocular includes two occluders-one for each eye-so monocular testing can be performed if desired.
The occluders are wing-like plastic plates that pivot up and down at the rear of the viewing head.
To block the vision of either eye, simply push down on the projecting tip of the appropriate occluder. (In normal binocular testing, the tips of the occluders are pushed up as far as they will go.) A major function of the occluders is in determining the existence of visual suppression: The mental blocking out of the image seen by one eye, so that the only image which registers in the mind is the one seen by the two eyes are fused into a single, integrated image in the mind.
The danger signal indicating possible suppression is a report by the test subject that the image, which should be visible to one of his/her eyes, does not appear.
In such cases, use the occluder to block the vision of the opposite eye. This will usually stimulate the “non-seeing” eye to work sufficiently hard so the “missing” image becomes visible. If this technique does not cause the “missing” image to appear, it may be concluded that all functional vision has been lost in that eye.
Telebinocular maintenance Under normal conditions of use, the Telebinocular needs no maintenance except for the occasional replacement of the lamp bulb. To minimize cleaning, the instrument should be protected by the dust cover when not in use.
Periodically, however, some cleaning will be necessary. The body of the Telebinocular should be dusted from time to time with a soft cloth or brush…and the lenses cleaned with a lens cloth or tissue.
If the unit has become very soiled, it may be washed with a mild soap-and-water solution.
THE TEST TARGETSTest #1: Far Point Visual Acuity Without occluding either eye this target will measure the acuity of the left eye, right eye and both eyes. Because both eyes are open, a visual suppression will be readily evident.
Levels of acuity: 20/200 to 20/20.
Test #2: Lateral Phoria This target measure horizontal binocular coordination, or muscle balance. Complaints of visual fatigue or headache are sometimes a result in part by an unusually high phoria, either lateral or vertical (see Test #3.) A normal range for Lateral Phoria is six (6) diopters or less of either esophoria or exophoria.
Test#3: Vertical Phoria
Similar to Test #2, this target is used to measure binocular coordination, but in the vertical plane. Seldom will anyone report a result other than “12” (orthophoria) on this test. A normal range is within one diopter of orthophoria, from “11” to “13”.
Test#4: Stereopsis This target measures stereopsis, or pure depth perception. Individuals with acceptable acuity and binocularity should perform well on this test. One symbol in each row stands out, appearing closer to the viewer. Each row is progressively more difficult in degree of stereopsis.
Test #5 and #6: Color Vision Two far point targets present three red/green and three blue/violet isochromatic symbols.
Presence of severe or mild color deficiency is indicated by the inability to rapidly identify the number presented.
Test #7: Near Point Acuity Presented with the cardholder set at Near Point, this tests acuity for a sixteen-inch distance. Without occlusion, readings for the left eye, right eye and both eyes are obtained.
The Keystone record form #5551 shown here simplifies recording and interpreting the results of the vision screening examination. The charts create a permanent record of a patients “visual profile” making it very easy to compare visual skills as time passes.
Scoring the tests is self-explanatory. A simple check mark at the last successful response is all that is done. To record uncorrected visions simply circle the last correct response; for correlated vision use a check mark. This helps you determine if one’s correction is doing its job.
The form is organized with a white “expected response” column in the center, with light gray and dark gray columns to both the left and right. As indicated, light gray indicates “Retest” and dark gray “unsatisfactory” responses. Individuals with unsatisfactory results may have a visual problem, and referral to a vision specialist should be made.
If referral is made, send a copy of your record form for the specialist to refer to.
*When retesting is indicated, the patient should not be rechecked immediately, but sometimes within a two-week period. If most scores indicate satisfactory visual skills, you may retest the patient only in those areas checked on the form as “doubtful”.
PREPARATION FOR TESTING
Readiness of the Equipment Normally, the Telebinocular should be placed on a desk or table providing sufficient room for the instrument, any accessories to be used, and the record form. (A table height of from 26 to 30 inches is recommended.) Place the Telebinocular near the edge of the table…and be sure that adequate knee room beneath the table is provided for the tester. Chairs for both tester and examiner should be straightbacked.
In the case of smaller children (through the ages of seven or eight), it may be desirable to have them stand during testing. A somewhat higher-than-normal table may be required, but most problems of posture can thus be eliminated.
Before testing begins, check the Telebinocular to make sure it is in proper working order. The unit should be connected to a standard 110-120 volt a.c. outlet and the lamp should light when the switch is turned on. (If necessary, the instrument should be dusted and the lenses cleaned with a soft lens tissue.) Check the test targets in the cardholder, too: The targets should be in proper sequence and the back plate of the holder moved far enough forward to keep the targets upright but not too tight to prevent easy change.
General test conditions Whenever possible, Keystone vision-screening test should be given in a quiet room with the lighting subdued and brilliant sunlight excluded. Testing can be performed in any area where traffic, noise, glare, or interruptions do not disconcert the tester or the examiner…and do not interfere with the accuracy or speed of the tests.
The examiner should be seated along the side of the table to the right of the test subject. It is important that he/she be able to face the subject, yet see and manipulate the targets in the cardholder.
Remember, too, to provide sufficient table space in front of the examiner for the record form.
Posture of the test subject Good body postured is important to good vision. So it is vital that proper posture be maintained during testing. An uncomfortable position will cause strain and distract the tester.
Seat the test subject in front of the Telebinocular and close enough to it so that his/her back and head are erect and his/her shoulder level, but relaxed. His/her feet should either be flat on the floor or comfortably placed on a rung of his/her chair or stool.