KNOWLEDGE


LANG-STEREOTEST® and LANG-STEREOPAD®

 Development and characteristics:

The LANG-STEREOTEST® was developed by the Swiss ophthalmologist Joseph Lang in the beginning of the 1980ties. The easy-to-use test is applied for the early detection of problems in stereoscopic vision in children and infants, but also in adults. Since many years, the test has been very much estimated by ophthalmologists, paediatricians and doctors working in the primary health care or in prevention. Two versions are available (LANG-STEREOTEST I and II) which only differ in the type of stereoscopic objects to be recognized. The LANG-STEREOTEST II additionally contains a picture that can be recognized with only one eye (a star). The test-plates are solid and can easily be carried around due to their handy postcard-size. These are distributed together with a fitting case, a brief instruction as well as a detailed test-description in several languages.

The LANG-STEREOPAD® is a new test system, using the same principle like the LANG-STEREOTEST I and II. It has been created to complement the main function of stereopsis screening with the preferential looking method (two alternative-forced choice task) and the assessment of stereopsis threshold in daily orthoptic practice.

The Importance of stereopsis:

Stereopsis or depth perception can be characterized as the highest degree of binocular vision. It therefore represents one of the most important partial functions of the human visual sense. In a limited extent, stereoscopic vision is actually possible with only one eye, for example due to perspective and shadow effects or parallel displacement, as well as with certain forms of strabismus (with the so-called anomalous retinal correspondence which occurs when non-corresponding retinal points have the same sense of visual direction). However, a completely missing or limited stereopsis can lead to severe handicaps in many life-domains and professions. This is a reason why this function should already be regularly examined in children and later within the education of jobs requiring an accurate stereoscopic vision.

 Functional principle of the LANG-STEREOTEST® and LANG-STEREOPAD®

The LANG-STEREOTEST® for the first time combined two functional principles of stereograms: The random dots of Julesz and the grid of cylinders of W.R. Hess. The random dots of Julesz are applied in different stereograms using polarized glasses or the red-green-glasses. Seen with only one eye (monocular vision), these stereograms do not show any shapes, while, upon binocular inspection, figures, typically in different depths, can be seen.

Grids of cylinders were invented by the Swiss ophthalmologist and physiologist W. R. Hess (Nobel Prize in 1949) in 1912. The images of the two eyes are separated by a system of tiny parallel cylindrical strips. Under each cylinder, there are two tiny strips of picture: one can only be perceived by the right, the other only by the left eye. The principle is used in modern lenticular lenses for 3D-printing.

Particularities in comparison to other stereo-test methods:

In contrast to the more traditional methods for examination of stereopsis, the two versions of the LANG-STEREOTEST® and also the LANG-STEREOPAD® require no haploscopic glasses and the eye movements of the patient can be much better observed by the examiner, thanks to the first-time combination of the two technologies mentioned above. Observing the patients eye-movements during testing has been noticed to be of particular importance in small children: once the child has recognized the different stereoscopic figures that are shown on the test panel, he subsequently will start to look repeatedly at these figures.
Other common, so-called haploscopic test-procedures, such as the Titmus-test are based on polarization and therefore require special glasses. The TNO-test uses the red-green-dissociation and hence needs corresponding red-green-glasses as well.  With the LANG-STEREOTEST®  and the LANG-STEREOPAD® however, the dissociation in haploscopic pictures is ensured by the half-cylindrical (lenticular) lens on the surface of the test-plate. While the LANG-STEREOTESTC has clearly been demonstrated to have the best testability in preverbal children of all common stereotests (AS Pai, K Rose, 2012), the LANG-STEREOPAD® - in the hands of the experienced examiner - could become the standard tool for first year stereopsis screening. 

Furthermore, due to the application of the random dots and the lacking of picture-outlines in the LANG-STEREOTEST® and in the LANG-STEREOPAD®, as well as in similar test using this principle (e.g. a version of the Randot-test), all monocular stereoscopic stimuli are completely eliminated. It is just the disparity of the figures represented, that generates a perception of depth and hence enables a precise perception of the shapes. Since primarily children are investigated, three objects have been chosen which are already common in this stage of life. The three objects – in the LANG-STEREOTEST I a cat, a star and a car, in the LANG-STEREOTEST II an elephant, a car and a moon – and 5 objects in the LANG-STEREOPAD differ in disparity and perceived distance. The most prominent objects are the cat (1200'') in the LANG-STEREOTEST I, the elephant (600'') in the LANG-STEREOTEST II, and the star (1000") in the LANG-STEREOPAD®.

The LANG-STEREOPAD® includes 6 magnetic test cards, each of them showing 1 test object of different disparity: star 1000'', car 600'', cat 400'', moon 200'', sun 100'' and star 50''. The test cards may be arranged freely on a test panel, either in visible position with vertically aligned lenticular grid, or positioned with horizontally aligned grid, so that the object is invisible. These features allow more sophisticated testing sequences like the preferential looking method, or staircase method or a combination of both. For further details please download the instruction brochure PDF below.

 

 PDF Instructions for LANG-STEREOTEST I and II

PDF Instructions for LANG-STEREOPAD

 

Scientific Papers PDF

Title Author Year
Video Game Vision Syndrome: A New Clinical Picture in Children? C.Rechichi, G.De Mojà, P.Aragona 2017 PDF
Statistical Evaluation in Pediatric Patient of LANG-STEREOTEST I for the Diagnosis of Microesotropia in Daily Practice

D. Allegrini, M. Spera-Orth, L. Rossetti, L. Ottobelli, A.C.Piantanida

2016 PDF

Binocular Sensory Status and Miscellaneous Tests

Optician

2011

PDF

Assessment of Adult Stereopsis Using the Lang 1 Stereotest: A Pilot Study

S. Brown, L. Weih, N. Mukesh, C. McCarty, H. Taylor

2001

 PDF

Testability of Refraction, Stereopsis, and Other Ocular Measures in Preschool Children: the Sydney Paediatric Eye Disease Study.

AS Pai,KA Rose, C. Samarawickrama, R. Fotedar, G. Burlutsky, R. Varma, P. Mitchell

2012

 PDF

The Congenital Strabismus Syndrome

J. Lang

2000

PDF

Scientific Essay: An Efficient Treatment and New Criteria for Cure of Strabismic Amblyopia: Reading and Bangerter Foils

J. Lang

1999

PDF

Pathophysiology of Binocular Vision and Amblyopia

J. Lang

1993

PDF

Eye Screening with the Lang Stereotest

J. Lang

1987

 PDF

Normosensorial Late Convergent Strabismus

J. Lang

1986

 PDF

The Congenital Strabismus Syndrome

J. Lang

2000

 PDF

The Optimum Time for Surgical Alignment in Congenital Esotropia

J. Lang

1984

 PDF

Microtropia

J. Lang

1983

 PDF

The 1982 Costenbader Lecture

J. Lang

1982

 PDF

Strabismus

M. C. Boschi, R. Frosini

1982

 PDF

Reading Capacity in Cases of Cured Strabismic Amblyopia

J. Lang

1980

 PDF

Major review: The underutilization of vision screening (for amblyopia, optical anomalies and strabismus) among preschool age children

 

M. S. Castanes

2003

 PDF

Stereoscopic Visual Acuity in Different Types of Amblyopia

L. Dorn, J. Petrinovic-Doresic

2007

 PDF

 

Weblinks:

Article on Stereopsis:   WIKIPEDIA

LANG-STEREOTEST:   WIKIPEDIA German