LANG-STEREOPAD 501 STAR 1000 Magnetic Test Card Instruction Manual
- June 9, 2024
- LANG-STEREOPAD
Table of Contents
Instructions for Use 
Purpose and indication
Purpose: The LANG-STEREOPAD® (Ref 501) is an orthoptic product for binocular
diagnosis and screening of stereopsis disorders in all age groups from 6
months of age
onwards, applicable by healthcare professionals.
Indication: Loss of stereopsis is considered a key symptom of amblyopia
(weak eye).
Therefore, non-recognition of random dot stereograms may indicate a previously
undetected, treatable disorder of binocularity (e.g., microstrabismus,
anisometropia).
Contraindication: There are no contraindications for the use of the LANG-
STEREOPAD®.
How the Test works
Please familiarise yourself with the LANG-STEREOPAD® by placing the STAR 1000
magnetic test card on the centre of the test panel in portrait position, with
the grooves of the lenticular lens oriented vertically (Fig. 1).
First, examine the test card with both eyes at your usual reading distance of
35–40cm.
Then cover one of your eyes for viewing.
Please use your corrective glasses or reading glasses for this exam.
For those with binocular stereo vision, the observer easily recognises the
test object with both eyes, which clearly stands out from the equally
patterned background. This depth effect is generated solely by the disparity
of the test object from the background. If only one eye examines the test
card, the test object disappears.
Now turn the test panel counterclockwise 90° so that it is now in landscape
position (Fig. 2).
The grooves of the lenticular lens on the test card now also run in the
horizontal direction. The test object is not recognisable in this position
either with double-eyed or with oneeyed observation.
A further 90° rotation of the test panel and/or the test card in the same
direction of rotation causes the grooves of the test card again to run
vertically, and the test object
is now seen upside down.
Fig. 1
Test panel in portrait position, test card with vertical grooves of lenticular
lens: Test object recognisable.
Fig. 2
Test panel rotated 90° counterclockwise, now in landscape position, test card
with horizontal lenticular lens: Test object not recognisable.
Fig. 3
Test card stack: The test cards are magnetically attached to each other. Their
grooves are automatically aligned in the same way.
Examiners with limited or no binocular stereo vision can also use the test.
The names of the various test objects and cross-disparations are noted on the
back of the test cards. There is also a rounded indentation in the lower
quarter of the back to help align the test card on the examination plate.
Please note that the test should always be performed with the test plate and
test cards resting on it, but never with the test cards alone. The test plate
should always be held still by the tester, not by the test person.
On pages 7-13 you will find a short introduction to the possible applications
of this test: Screening, Preferential Looking Method and Stereo Threshold.
Detailed information on the application as well as technical specifications
can be found from page14 onwards, general information as well as help in case
of difficulties from page 17 onwards.
Screening and Assessment of Stereopsis
The subject is presented a single test card in the middle of the test panel
(portrait or landscape position) with vertical orientation of the grooves of
the lenticular lens (page 5, Fig. 1).
Subjects with Stereopsis
Subjects with stereopsis usually recognise the test object within a few
seconds.
There are two ways to confirm this result:
- Turn the test panel 90° counterclockwise (from portrait to landscape position). The test object disappears. Turn the test panel again 90° (from landscape to upside down portrait position): The test object can be identified upside down. The subject should comment on the observed changes at each step (page 8, Fig. 4).
- Attaching a second test card with a different disparity below or next to the first test card on the test panel, also with vertical lenticular lens. The subject should then point to the test object which stands out more prominently from the background (Fig. 5).
Subjects with poor or absent Stereopsis
When being asked what they can see, subjects without stereopsis typically keep
searching for recognisable test objects, until they answer ‘nothing’. The
examiner should avoid providing the subject with assistance, for example by
asking questions in a suggestive manner or presenting a one-eye-visible image
of the test object.
Fig. 4
Confirmation step 1 in subjects with stereopsis:
Turning the test panel 90° counterclockwise will cause the test object to
disappear.
Further rotation of the test panel 90° in the counterclockwise direction leads
to the reappearance of the test object, but upside down.
Fig. 5
Confirmation step 2 in subjects with stereopsis: By attaching a second test
card with different disparity on the panel, the two test objects show a
different prominence from the image plane, which is to be compared by the
subjects.
Preferential Looking Procedure
In this procedure two test cards are attached to the test panel of the LANG-
STEREOPAD® at the same time: one with vertically aligned grooves of the
lenticular lens and thus a recognisable stereogram, the other next to or below
it with a horizontal lenticular lens and therefore an unrecognisable
stereogram (Fig. 6).
Subjects with Stereopsis
The subject with stereopsis will tend to turn to the card with the
recognisable stereogram.
The finding can be confirmed as follows: Rotate the test panel 90° counter-
clockwise (Fig. 7). The subject with stereopsis now recognises the test object
on the second test card, which was previously not recognisable. The previously
identified test object has now disappeared.
Subjects with poor or absent Stereopsis
In the absence of stereopsis, however, the subject’s gaze alternates between
the test cards, before it begins to wander.
Triple Selection Arrangement
Instead of using two test cards (two-alternative forced-choice task), the same
procedure can be used simultaneously with three test cards (Fig. 8). The
probability of a random hit is thereby reduced from 50% to 33%.
Fig. 6
Test panel in landscape position, right test card with identifiable STAR 1000,
left test card with horizontal lenticular lens and hidden CAT 400.
Fig. 7
Confirmation step by turning the test setup 90° counterclockwise:
The now above STAR 1000 is hidden.
The test object CAT 400 becomes visible on the test chart with vertical
lenticular lens below.
Fig. 8
Example of triple selection: After rotating the test arrangement by 90°
counterclockwise from landscape to portrait position, the STAR 1000 in the
middle disappears.
Instead, the CAT 400 (top) and the CAR 600 (bottom right) become recognisable
.
Assessment of Stereo Threshold with Staircase Method
The stereo threshold is defined as the lowest disparity that a test object
must have for the subject to see it against the background.
After stereopsis has been detected during screening, the stereo threshold can
be determined in a further step. In this case, starting from the screening
test arrangement with the test card with the largest transverse disparity
(STAR 1000), test cards with descending transverse disparity are presented
successively (staircase method).
The disparity of the test object with the least disparity, which is still
recognised by the subject, is recorded as the stereo threshold.
The cards CAR 600, CAT 400, MOON 200, SUN 100, and finally STAR 50 are placed
step by step on the test panel below the first test card. Already recognised
test cards can be continuously pushed up-wards and removed or left for
comparison (Fig. 9).
Fig. 9 Determination of the stereo threshold: first three steps
Disparities and Stereo Objects of the six Test Cards
| STAR 1000’’ | MOON 200’’ |
|---|---|
| CAR 600’’ | SUN 100’’ |
| CAT 400’’ | STAR 50’’ |
Combination of Staircase and Preferential Looking Method
A combination of the stepwise (or staircase) method and preferential looking
techniques may also be used. For this purpose, two test cards with test
objects are arranged in descending disparity on the front and back of the test
panel in such a way that the test card with the next smallest disparity
becomes recognisable after 90° rotation or turning of the test panel (Fig. 10,
Fig. 11).
Fig. 10
Example with four disparity steps: 400-200-100-50: Preparation of test panel.
Front: left CAT 400 recognisable, right MOON 200 invisible.| Back: left STAR
50 recognisable, right SUN 100 invisible.
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| 
Fig. 11
- Presentation of front in landscape position: CAT 400 visible on test card.
- 90° counterclockwise rotation to portrait position: CAT disappears, and MOON 200 appears on upper test card.
- Turn to back: SUN 100 visible on lower test card.
- 90°counterclockwise rotation to landscape position STAR 50 visible on left card, while MOON 200 disappears.
Test Design and Objective
The LANG-STEREOPAD® is a test system for the detection and assessment of
binocular stereoscopic vision in adults and children. It examines global near
stereopsis using random-dot stereograms. Random dots are patterns that serve
to camouflage the test objects against the same patterned background. The
image separation of the stereograms is performed by an optical lenticular
lens, hence no haploscopic test glasses are needed. The LANG-STEREOPAD® uses
the same technical principle as the LANG-STEREOTEST®, but allows more
sophisticated examination possibilities. The test cards are presented by the
examiner individually or in groups on the test panel. The order and
arrangement of the test cards can be varied depending on the purpose of the
examination. The variability of arrangement and sequence provides – in con-
trast to many other stereo tests – particularly reliable and easier-
tointerpret test results. The guessing of the test objects or recognition in
the case of monocular viewing is prevented by the perfect camouflage of the
test objects and the square shape of the test cards. The test consists of a
red test panel with a soft PVC surface and a stainless-steel core, as well as
six square magnetic test cards, which can be placed in any position on either
side of the test panel. Each test card contains one of five different test
objects that can be seen in presence of binocular stereoscopic vision. The
test objects have disparities in the increments of 1000, 600, 400, 200, 100,
and 50 sec- onds of arc. The respective test object can only be perceived if
the test card is oriented so that the lenticular lens runs in the vertical
direction. If the test card is viewed with only one eye or rotated 90° so that
the lenticular lens is horizontal, the test object remains invisible.
Detection of Random-Dot Stereopsis
Random-dot stereogram testing is widely considered to be one of the most
important detection methods of binocular vision. Randomdot stereopsis is a
strong indicator of a normally functioning visual system. Random-dot
stereopsis can be detected in children from only a few months old. Several
congenital or acquired visual disorders and conditions are, however,
associated with a limitation or loss of random-dot stereopsis, particularly
amblyopia, multiple forms of strabismus and anisometropia.
The LANG-STEREOPAD® (like the LANG-STEREOTEST®) allows the detection of
binocular stereo vision, without the use of test glasses. In addition, the
random-dot stereo threshold can be determined in six gradations. The stereo
threshold depends upon the age of the subject as well as the presence of
visual disorders which are associ- ated with limitations of stereopsis. The
modular design of the test system allows its use in all age groups, as well as
in persons with cerebral impairment with or without aphasia.
Preferential Looking Procedure especially for Preverbal Infants
The preferential looking method is suitable for testing visual functions
especially in young children or in persons with a cerebral impairment, who
cannot verbally express their perception. Simultaneously, the subject is
presented with two images of the same kind. One of them contains a visual
stimulus, the other contains no visual stimulus. With simultaneous
presentation of both images, the subject’s gaze, after the needed time of
exposure, usually sticks to the one with the visual stimulus. If both images
are considered the same length on average, or if the subject loses interest in
the images, it is assumed that he or she lacks the ability to perceive the
visual stimulus and distinguish between the two images.
The LANG-STEREOPAD® allows different variants of the preferential looking
method which can be used for the examination of preverbal infants and persons
with speaking disorders. Two or more test cards are simultaneously presented,
of which only one contains the stereoscopic stimulus (card with vertical
lenticular grid, see pages 5-6). It is important that the examiner closely
observes the gaze movements of the subject in order to determine whether,
after a longer period of observation, the gaze sticks to the test card with
the stereoscopically recognisable test object. This specific fixation
behaviour is considered a criterion of distinction between subjects with and
without stereopsis.
General Recommendations and Notes
Visual acuity, Refraction Anomalies
The LANG-STEREOPAD® was designed primarily for subjects with normal visual
acuity. For the examination of children under one year or for patients with
reduced visual acuity, the two test cards with the largest cross disparities,
STAR 1000 and CAR 600, should preferably be used, as these have a slightly
coarser dot pattern than the other
test cards. Patients with refractive anomalies should wear their own
prescription glasses or contact lenses for the test.
Viewing Position
The viewing should be done at the preferred reading distance (about 35–40cm).
The test cards should always be presented or viewed on the test panel. Under
no circumstances should they be held by the examiner or the patient during the
test. The test panel should either be held steady by the examiner or placed on
the stand (sold separately) at the desired angle.
Alignment of the Test Panel, Arrangement of the Test Cards The test panel can
be used on both sides and in both portrait and landscape position. The test
cards can be freely placed on it. The simultaneous presentation of more than
three test cards is not recommended except for the preferential looking.
The test cards should be presented either with a vertical or a horizontal
lenticular lens, and not obliquely. The test cards with asymmetrical test
objects (CAR 600, CAT 400 and MOON 200) can also be used upside down to assess
subjects who are already familiar with the test object. One can ask which
direction the car is driving , or on which side the tail of the cat lies. With
the test object moon (MOON 200) the patient can be asked to show the curvature
with his or her finger. For the test objects star (STAR 1000, STAR 50) and sun
(SUN 100), the number of points or sunbeams can be queried.
Cooperation of the Subject
The cooperation of the patient and any accompanying person is very important.
The test should therefore be carried out with sufficient time and in quiet
environmental conditions. Pressure from the examiner or other people present
should be avoided. The subject should be given some time to adapt and find the
ideal viewing position. Subjects should be asked if they can recognise
something on the grey surface. Suggestive questions should be avoided. They
may be invited to point at the recognised test object and name the object.
This is especially useful for the preference looking process.
Examination of Preverbal Infants and Adults with Loss of Speech
The LANG-STEREOPAD®, in contrast to most other stereo tests, offers a
multitude of possibilities for examining preverbal children in order to obtain
a reliable result. Another application is the assessment of stereopsis in
patients with aphasia, for example due to brain damage. In addition to the
cooperation of the accompanying parent, the examination of babies or
particularly lively preverbal toddlers requires patience and good preparation.
In order to arouse the children’s in- terest, the LANG FIXATION CUBE can be
shown in advance. All more complex examinations, especially with the
preferential looking procedure, must be prepared and practiced so that a
seamless examination process is ensured, and the subject’s attention is not
lost prematurely. It should also be prevented that small children grab and
move the test cards on the test panel, and then become more interested in this
‘game’ than in the recognisable test objects.
Test Card Back Side
The test can also be performed by examiners who themselves have no stereo
vision. On the back side of the test cards are the names of the test objects
followed by a number corresponding to the transverse disparity in seconds of
arc.
The orientation of the test card and the lenticular lens can be quickly
scanned using the rounded dent in the bottom quarter of the back.
However, the back of the test cards should never be shown to the subjects.
Stacking and Automatic Alignment
If the examiner wants to place the test cards in a specific order on the test
panel, the test cards can be prepared in a stack. The arrangement of the
magnets in the test cards
ensures that the test cards align themselves so that the grooves of their
lenticular lenses run in the same direction (see page 5, Fig. 3).
Difficulties with Assessment If a subject is unable to recognise a test
object, the examiner should check if the lens grid of the presented test
object is aligned vertically, and the viewing position and angle are correct.
Although some patients recognise the test objects as surfaces that are raised
from the background, they may be unable to name their shape. For example, a
child may identify another familiar object (‘fish’, ‘turtle’) instead of the
car or recognise a ‘dog’ or ‘mouse’ instead of the cat. It is advisable not to
rectify this immediately, but to offer the test subject another test card and
to have him or her describe which of the two objects continues to stand out
from the background.
As a rule, leading questions such as ‘Don’t you see a car?’ should be avoided.
On the other hand, the examiner can introduce a one-eye- visible stimulus,
e.g., by touching the test object with a pointer. For some subjects, this
assistance can lead to ‘jumping in’ of the corresponding stereo columns in the
visual cortex and full random-dot stereo perception.
Especially lively children sometimes feel a certain compulsion to succeed and
then try to guess the test objects. By rapidly turning or reversing the test
panel – especially when two test cards with different orientations of the
lenticular lens are used – those guessing can be easily detected. You can then
do some ’magic’ with the LANG-STEREOPAD® and perform a quick change of the
test objects by means of panel rotation or reversing. The high optical quality
of the lenticular lens and dot pattern used makes it impossible to guess or
recognise test objects whose lenticular lens is not aligned vertically.
Interpretation, Repetition of Test
The detection of binocular stereo vision by means of LANG-STEREOPAD® does not
rule out disorders of the visual system.
The stereo threshold achieved on the LANG-STEREOPAD® is age-dependent and may
differ from stereo thresholds achieved in other stereo tests.
Of course, examination with the LANG-STEREOPAD® does not replace visual acuity
testing.
The interpretation of the findings must be made in the clinical context.
Patients with conspicuous findings should therefore be further assessed with
complementary tests or
re-examined later.
Screening of stereopsis in children should be repeated according to current
guidelines.
The responsibility for diagnostic and therapeutic decisions lies entirely with
the user.
Any liability for incorrect decisions is rejected.
Storage and Care
The test plate and the test cards are easy to clean but should be handled with care. The surfaces can be cleaned with a damp cloth, if necessary, with a little washing-up liquid. Scratching or abrasive materials and solvents must not be used. When not in use, the test plate and test cards should be stored in the product box supplied.
Warnings
| Exposure to high heat or sunlight may cause deformation and discolouration
of the test cards or the test plate, rendering them unusable.
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| The test cards must always be stored in a dry place.
| The test cards and the plate support (sold separately) contain magnets that
generate a magnetic field that could be harmful to pacemaker wearers.
Avoid exposure of electronic devices (mobile phones, computers, tablets, etc.)
to the magnetic parts of the test. No liability is accepted for damage to
persons or objects due to magnetic causes.
The LANG-STEREOPAD® should not be left for children to play with.
Check the functionality of the test cards before each use.
Serious incidents must be reported to the manufacturer and the competent
authority.
Development, Design, Production and Distribution
LANG-STEREOTEST AG, 8700 Küsnacht, Switzerland
Scientific literature
Rowe, Fiona J. PhD, et al., Strabismus 2019 Jul 22: 1-9 Comparative analysis
of the Lang-Stereopad in a non-clinic population.
Piantanida, A.C., et al., Transactions 40th Meeting of the European
Strabismological Association Helsinki 2019: 189-194 Statistical Evaluation in
Pediatric Patients of the New Lang-Stereopad Test: A Preliminary Report
Online LANG-STEREOPAD® – Intro und Tutorial
REF| 501-en
2022-06/ V2.0
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****| LANG-STEREOTEST AG
Postfach 137
CH-8700 Küsnacht
Switzerland
| A.Lang-Lieder
Murstrasse 48
A-6063 Rum
Austria
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