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Wheatstone stereoscope

A Wheatstone stereoscope is a stereoscope that shows each eye its own target through two separate viewing tubes or mirrors. The Brewster stereoscope separates the eyes with a septum instead. The mirrors of the Wheatstone design also let the clinician test and train at different simulated distances.1

Wheatstone invented the stereoscope in 1838 and was the first to recognize that stereopsis occurs when horizontally disparate retinal elements are stimulated at the same time. The two images fuse into a single percept seen in depth as long as the fused image lies within Panum's area, and vertical displacement produces no stereoscopic effect.2

The Bernell Variable Prismatic Stereoscope is the Wheatstone stereoscope most often used to treat nonstrabismic binocular vision disorders. The major amblyoscope is another Wheatstone-type instrument, used mainly to diagnose and treat strabismus.3

More detail

The Bernell instrument has a working distance of 33 cm and no lenses, so the accommodative demand is 3 D, and plus or minus lenses change that demand. Moving the two halves apart creates base-in vergence demand, moving them together creates base-out demand, and the prismatic demand is read directly off the instrument's scale. In therapy the stereoscope is used to increase the amplitude of negative and positive fusional vergence and to shorten the latency and raise the velocity of the fusional vergence response.3

Sources (23)
  1. Scheiman and Wick, Clinical Management of Binocular Vision, ch. 5
  2. von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 2
  3. Scheiman and Wick, Clinical Management of Binocular Vision, ch. 6
  4. Brewster, D. (1856). The stereoscope: its history, theory and construction. London: John Murray.
  5. Klyne, M.A. (1950). Wheatstone and the Origins of Moving Stereoscopic Images. The Photographic Journal, 90B(1), pp.44-47.
  6. Platt, B.C. and Shack, R. (2001). History and Principles of Shack-Hartmann Wavefront Sensing. Journal of Refractive Surgery, 17(5), pp.S573-S577.
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  9. PubMed Central: PMC6802785
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  22. onlinelibrary.wiley.com: 9783527648443.ch2
  23. collection.powerhouse.com.au: 550337

Reviewed October 2026

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