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Overestimation of stereo thresholds by the TNO stereotest is not due to global stereopsis

Lookup NU author(s): Dr Kathleen Vancleef, Professor Jenny ReadORCiD, Dr Ignacio Serrano-PedrazaORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2017 The College of Optometrists. Purpose: It has been repeatedly shown that the TNO stereotest overestimates stereo threshold compared to other clinical stereotests. In the current study, we test whether this overestimation can be attributed to a distinction between 'global' (or 'cyclopean') and 'local' (feature or contour-based) stereopsis. Methods: We compared stereo thresholds of a global (TNO) and a local clinical stereotest (Randot Circles). In addition, a global and a local psychophysical stereotest were added to the design. One hundred and forty-nine children between 4 and 16 years old were included in the study. Results: Stereo threshold estimates with TNO were a factor of two higher than with any of the other stereotests. No significant differences were found between the other tests. Bland-Altman analyses also indicated low agreement between TNO and the other stereotests, especially for higher stereo threshold estimates. Simulations indicated that the TNO test protocol and test disparities can account for part of this effect. Discussion: The results indicate that the global - local distinction is an unlikely explanation for the overestimated thresholds of TNO. Test protocol and disparities are one contributing factor. Potential additional factors include the nature of the task (TNO requires depth discrimination rather than detection) and the use of anaglyph red/green 3D glasses rather than polarizing filters, which may reduce binocular fusion.

Publication metadata

Author(s): Vancleef K, Read JCA, Herbert W, Goodship N, Woodhouse M, Serrano-Pedraza I

Publication type: Article

Publication status: Published

Journal: Ophthalmic and Physiological Optics

Year: 2017

Volume: 37

Issue: 4

Pages: 507-520

Print publication date: 01/07/2017

Online publication date: 23/03/2017

Acceptance date: 09/02/2017

Date deposited: 03/05/2017

ISSN (print): 0275-5408

ISSN (electronic): 1475-1313

Publisher: Wiley-Blackwell


DOI: 10.1111/opo.12371


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