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zone of clear single binocular vision

The zone of clear single binocular vision is a graph of the ranges of accommodative and vergence stimuli through which a patient can keep binocular vision clear and single.1 The findings usually plotted are the dissociated phoria, base-in and base-out to blur, break and recovery, negative and positive relative accommodation, the amplitude of accommodation, and the near point of convergence.2

In the classic method, the vertical sides of the zone represent the vergence limits of clear single binocular vision, and their slope is the reciprocal of the stimulus AC/A ratio.1 Graphical analysis uses the zone to judge whether a patient can expect clear, single, and comfortable binocular vision.2 Patients with fusional vergence dysfunction often have normal phorias and AC/A ratios but reduced fusional vergence amplitudes, so their zone is small.3

More detail

A proximal-based interactive model predicts that the boundaries of the zone are two straight lines that are not parallel. The convergence side slants more than the divergence side at high levels of accommodation, and the top of the zone is not parallel to the bottom because convergence drives extra accommodation.1

Sources (24)
  1. Scheiman and Wick, Clinical Management of Binocular Vision, ch. 16
  2. Scheiman and Wick, Clinical Management of Binocular Vision, ch. 2
  3. AOA Optometric Clinical Practice Guideline, Care of the Patient with Accommodative and Vergence Dysfunction
  4. Gifford, K.L., Gifford, P., Hendicott, P.L. and Schmid, K.L. (2020). Zone of Clear Single Binocular Vision in Myopic Orthokeratology. Eye & Contact Lens, 46(2), pp.82-90.
  5. Hofstetter, H.W. (1945). The zone of clear single binocular vision. Part I. American Journal of Optometry, 22(7), pp.301-333.
  6. Hofstetter, H.W. (1945). The zone of clear single binocular vision. Part II. American Journal of Optometry, 22(8), pp.361-384.
  7. Rutstein, R. and Daum, K. (1997). Anomalies of Binocular Vision: Diagnosis & Management. St. Louis: Mosby.
  8. Scheiman, M. and Wick, B. (2014). Clinical Management of Binocular Vision. 4th ed. Philadelphia: Lippincott Williams & Wilkins.
  9. kesona.com: binocular-vision-anomalies
  10. oepf.org: binocular-anomalies-5th-edition-2-volume-set
  11. PubMed Central: PMC9446491
  12. PubMed: 7843910
  13. PubMed: 3750876
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  15. JAMA Network: 622425
  16. EyeRounds (University of Iowa): bhola-binocularvision.htm secondary
  17. American Optometric Association: Care%20of%20Patient%20with%20Accommodative%20and%20Vergence%
  18. PubMed: 31008827
  19. modestovision.com: seeing-the-whole-picture-understanding-single-vision-glasses
  20. PubMed Central: PMC8409099
  21. eyenews.uk.com: binocular-single-vision-bsv
  22. PubMed: 8728494
  23. reviewofmm.com: the-importance-of-binocular-vision-in-managing-myopia-progre
  24. Wolters Kluwer journal: zone_of_clear_single_binocular_vision_in_myopic.4.aspx

Reviewed October 2026

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