The Lang Stereotest was created to simplify stereopsis
screening in children. It is based on two principles: random dots and
cylindrical gratings. Random dots of Jules are currently used in stereograms.
When seen monocularly, they do not provide form cues, whereas in binocular
vision stereoscopic forms are recognized. The disadvantage of most random dots
is that they require red/green or polarized glasses.
Cylindrical screens were invented by the Swiss
Ophthalmologist and physiologist W. R Hess (Nobel Prize 1949) in 1912. The images of the two
eyes are separated by a system of fine parallel cylindrical strips. Beneath each
cylinder there are two fine strips of pictures, one seen by the right, the other
seen by the left eye. These two methods were combined for the first time in the
Lang Stereotest. This technique has two advantages: no glasses are required and
the eye movements of children can be easily observed.
The Lang Stereotest I measures disparities: Star 600, Cat
1200 Car 550 seconds of arc
Lang Stereotest l
006x Lang Stereotest I .......... $100.50 
007x Lang Stereotest II ......... $100.50
Lang
Stereotest Technical Article
Pediatric
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