Intended use and main features Lang-Stereotests® are orthoptic products for binocular diagnostics and screening of disorders of stereoscopic vision in adults and children, for medical professionals. The Lang-Stereotest® is used for rapid screening of stereopsis vision in all age groups from 6 months of age. Since loss of stereopsis is considered a key symptom of amblyopia (lazy eye), failure to recognise random dot stereograms may indicate a previously undetected, treatable disorder of binocularity (e.g., microstrabismus, anisometropia). Lang-Stereotests® have proven to be highly specific and highly sensitive for stereo vision. Thanks to the unique combination of random dots and a lenticular lens, no special glasses are needed, and the eye movements of the subject may be easily observed.
The test exists in the versions Lang-Stereotest® I and II, and the revised versions I-R and II-R.
The Lang stereotest® I-R is a revised version of the Lang-Stereotest® I. This revised version has improved optical and print quality over the earlier version and has no monocular clues when used correctly. Also new is a quick reference guide in English on the back of the test card, with schematic diagram for correct use, mirror image arrangement of stereo objects and typical pattern of eye movements in stereopositive subjects.
Important note: Information on clinical data and evaluations can be found on the literature page (Features of the Lang-Stereotest®, scientific articles). All contents refer exclusively to the original Lang-Stereotest® and may lead to false statements if applied to other similar or copied products.
Examination & Application
Examination (see also diagram on the back of the test)
Make sure the subject is wearing his/her corrective glasses or reading glasses (if necessary).
Avoid reflections from lamps or windows.
Do not hand the test card to the subject. The latter may find the optimal viewing position by slight head movements.
Hold the test card vertically at a reading distance of 30-40cm.
Avoid moving or wiggling the test card during the test.
Ask, "Can you see anything?" Refrain from giving help, asking suggestive questions, or mentioning the 3D objects.
Observe the subject’s eye movements
Refining the examination
If the subject already knows the 3D objects, use the test card upside down or show two tests, one in horizontal and one in vertical position where the 3D objects disappear.
Switch to the other version of the Lang-Stereotest® when retesting or use the Lang-Stereopad® for more in-depth testing (for the preferential looking method or the stereo threshold).
To confirm a positive result, have the subject close one eye while looking at the 3D objects. The test figures must disappear during this process
Results of Screening
Positive: Correctly naming or pointing all test figures. The eye movement pattern describes a triangle in the Lang-Stereotest® I-R and a quadrilateral in the Lang-Stereotest®II-R. -> No further examination required.
Negative: No 3D object can be detected. Eyes are scanning the test plate and then shift away from it. -> Refer patient to orthoptic eye specialist for further examination of stereoscopic vision and visual acuity.
Doubtful: One or more objects may be localized but are not being identified correctly. Eyes are scanning the test plate. -> Repeat test after break, without giving suggestions. -> Refer patient to orthoptic eye specialist for further examination of stereoscopic vision and visual acuity.
Common mistakes and how to avoid them
The test must be performed by an experienced examiner, i.e. self-testing is not reliable because it can give false positive results.
The test card must not be moved or tilted during the examination. The patient must look at the card calmly and wait for the test figures to appear.
The recognition takes some time. It is important to perform the examination without putting pressure on the patient. No hints should be given, certainly not the names of the test figures.
Important note Lang-Stereotests® are not a substitute for a visual acuity test or a specialist eye examination. A positive screening result only indicates the presence of random dot stereoscopic vision (global stereopsis) but does not exclude other visual disorders. A negative screening result alone does not prove a visual disorder. Users must therefore be well acquainted with the test. The revised test versions (-R) have improved print and image quality compared to the previous versions Lang-Stereotest® I and Lang-Stereotest® II. On the back of the test there are brief instructions and a schematic drawing for correct use.
3D test figures and cross-disparities of the Lang-Stereotest® I-R
Reading distance: 30-40 cm (10-15 inches)
REF 103, CE mark, Medical Device Class I, compliant with Regulation (EU) 2017/745/EU
Format: 145 x 95 mm | thickness 1.5 mm
(5.71 x 3.75 Inches | 0.08 Inches)
Weight without envelope: 20 g
Supplied with envelope bag
Operating instructions are in the envelope
Manufactured in Switzerland, developed by Lang-Stereotest AG. All rights reserved.
Care, Storage and Warning Notices
Store the test in the case provided.
Please check functionality before each use. Exposing the test card to heat or sunlight may cause deformation and render the test card unusable.
Clean the test with a dry or slightly damp cloth. Liquids can dissolve the back of the card.
Serious incidents must be reported to the manufacturer and the competent authority.