random-dot stereogram
A random-dot stereogram is a pair of random dot patterns that each look like random noise to one eye alone.1 The two patterns are identical except for a central region shifted horizontally in one of them, and fusing the pair lets the retinal disparity of that region make a figure stand out in depth.1
Neither monocular image contains any contour of the hidden figure, and the figure is seen only through stereopsis.1 Random-dot stereograms therefore showed that stereopsis does not depend on monocular cues or on recognizing a shape first.1 Seeing the figure requires global stereopsis, the pooling of information from the entire stereogram by the visual system, a harder task than the local stereopsis tested with contour targets such as the Titmus circles.1,2
Random-dot tests leave the patient no way to guess what the figure is or where it lies. The tests thereby exclude the monocular cues that can contaminate contour tests.3 Clinical examples include the random-dot E test, the TNO test and the Lang I and II tests.2,3
More detail
In the random-dot E test the patient views two cards at 50 cm through polarizing spectacles and indicates which card contains the E, and increasing the testing distance quantifies the result.3 Normal stereoacuity, 15 to 60 seconds of arc on any of the random-dot stereograms, marks normal binocular function.4
Random-dot testing is not the same as testing stereopsis under ordinary seeing.1 One study found that 40% of 162 normal children aged 4 1/2 to 5 1/2 years had random-dot stereopsis of less than 40 seconds of arc, which casts doubt on the test's power to separate normal from abnormal children.1
Sources (10)
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 2
- Eperjesi and Rundström, Practical Binocular Vision Assessment, ch. 7
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 15
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 16
- Julesz, B. 1971. Foundations of Cyclopean Perception. Chicago: University of Chicago Press.
- Mustillo, P. 1985. Binocular mechanisms mediating crossed and uncrossed stereopsis. Psychological Bulletin, 97(2), pp.187-201.
- Norcia, A.M. and Tyler, C.W. 1984. Temporal frequency limits for stereoscopic apparent motion processes. Vision Research, 24(5), pp.395-401.
- Patterson, R. and Fox, R. 1984. The effect of testing method on stereoanomaly. Vision Research, 24(5), pp.403-408.
- Rutstein, R. and Daum, K. 1997. Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
- Wilcox, L.M. and Allison, R.S. 2009. Coarse-fine dichotomies in human stereopsis. Vision Research, 49(22), pp.2653-2665.
Reviewed October 2026
Related terms
Nearby in the glossary
- random-dot stereogram
- recession
- resection
- retinal rivalry