Accommodation and convergence – ratios, linkages, styles and mental somersaults

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Horwood, A. ORCID: https://orcid.org/0000-0003-0886-9686 (2018) Accommodation and convergence – ratios, linkages, styles and mental somersaults. In: 13th Bielschowsky Lecture. Joint ISA/AAPOS Conference 2018, 18-20th March 2018, Washington DC, USA, e3.

Abstract/Summary

A relatively fixed relationship between convergence and accommodation appears to be fundamental to binocular vision and its disorders. The accommodative convergence to accommodation ratio (AC/A) has traditionally been considered a major explanatory factor, but it fits only a small number of clinical diagnoses and fails to explain others. An alternative model, based on the different weights the visual system places on the main cues to target position in depth, fits concomitant strabismus, heterophoria and convergence and accommodation anomalies more comprehensively. Typical accommodation can be surprisingly variable and many intermittently-strabismic people still use binocular disparity as their primary visual cue, with blur and proximal/looming cues having less weight. The convergence-accommodation to accommodation (CA/C) linkage is therefore more important than the AC/A relationship in the majority of typical and atypical cases. Between-diagnosis style differences in the relative balance between these relationships can explain many clinical findings. Instead of “accommodation drives convergence”, or “convergence drives accommodation”, we should instead think of the visual and non-visual cues which drive both systems more independently and flexibly.

Item Type	Conference or Workshop Item (Paper)
URI	https://reading-clone.eprints-hosting.org/id/eprint/80021
Refereed	No
Divisions	Life Sciences > School of Psychology and Clinical Language Sciences > Development Life Sciences > School of Psychology and Clinical Language Sciences > Perception and Action
Uncontrolled Keywords	Accommodation; Convergence; Ratios; Model; Intermittent strabismus
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Date Deposited:	24 Oct 2018 11:38	Date item deposited into CentAUR
Last Modified:	23 Jan 2024 18:34	Date item last modified

References

1. Maddox E. Investigations on the relationship between convergence and accommodation of the eyes. J Anat. 1893;20:475-505, 65-84. 2. Hoyt C, Taylor D. Pediatric Ophthalmology and Strabismus. 4th ed. Edinburgh: Elsevier Saunders; 2012. 3. Rainey BB, Goss DA, Kidwell M, Feng B. Reliability of the response AC/A ratio determined using nearpoint autorefraction and simultaneous heterophoria measurement. Clin Exp Optom. 1998;81(5):185-92. 4. Havertape SA, Cruz OA, Miyazaki EA. Comparison of methods for determining the AC/A ratio in accommodative esotropia. J Pediatr Ophthalmol Strabismus. 1999;36(4):178-83. 5. Murray C, Newsham D. Normative Values for the Accommodative Convergence to Accommodation Ratio (AC/A). Invest Ophthalmol Vis Sci. 2010;51(5):801. 6. Pankhania SR, Firth AY. The response AC/A ratio: differences between inducing and relaxing accommodation at different distances of fixation. Strabismus. 2011;19(2):52-6. 7. Gage J. A comparison of AC/A ratio measurement using the gradient method at near and distance fixation. Brit Orthoptic J. 1996;53:25. 8. Jackson JH, Arnoldi K. The Gradient AC/A Ratio: What's Really Normal? Am Orthopt J. 2004;54:125-32. 9. Horwood A, Riddell P, Turner JE, Houston SM, editors. Assessment of the AC/A ratio using a remote haploscopic photorefractor. IX International Orthoptic Congress; 1999; Stockholm, Sweden: Berufsverband der Orthoptisten. 10. Turner JE, Horwood AM, Houston SM, Riddell PM. Development of the response AC/A ratio over the first year of life. Vision Res. 2002;42(22):2521-32. 11. Judge SJ. Can current models of accommodation and vergence control account for the discrepancies between AC/A measurements made by the fixation disparity and phoria methods? Vision Res. 1985;25(12):1999-2001. 12. Horwood A, Riddell P. The use of cues to convergence and accommodation in naïve, uninstructed participants. Vision Research. 2008;48(15):1613-24. 13. Ludden SM, Horwood AM, Riddell PM. Children’s Accommodation to a Variety of Targets – A Pilot Study. Strabismus. 2017;25(3):95-100. 14. Roberts TL, Manny RE, Benoit JS, Anderson HA. Impact of Cognitive Demand during Sustained Near Tasks in Children and Adults. Optom Vis Sci. 2018;95(3):223-33. 15. Horwood A, Riddell P. Differences between naïve and expert observers’ vergence and accommodative responses to a range of targets. Ophthalmic & Physiol Optics. 2010;30:152-9. 16. Horwood A, Riddell P. The Clinical Near Gradient Stimulus AC/A ratio correlates better with the response CA/C ratio than with the response AC/A ratio. Strabismus. 2013;21(2):140-4. 17. Rosenfield M, Ciuffreda KJ, Chen HW. Effect of age on the interaction between the AC/A and CA/C ratios. Ophthalmic Physiol Opt. 1995;15(5):451-5. 18. Horwood A, Riddell P. Hypo-accommodation responses in hypermetropic infants and children. BJOphth 2011;95( 2):231-7. 19. Horwood AM, Toor SS, Riddell PM. Change in convergence and accommodation after two weeks of eye exercises in typical young adults. J AAPOS. 2014;18(2):162-8. 20. Mollon JD, Bosten JM, Peterzell DH, Webster MA. Individual differences in visual science: What can be learned and what is good experimental practice? Vision Res. 2017;141:4-15. 21. Horwood AM, Riddell PM. Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus. Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS}. 2014;18(6):576-83. 22. Horwood A, Riddell P. Developmental changes in the balance of disparity, blur and looming/proximity cues to drive ocular alignment and focus. Perception. 2013;42:693-715. 23. Toor S, Horwood AM, Riddell P. Asymmetrical accommodation in hyperopic anisometropic amblyopia. British Journal of Ophthalmology. 2017; Oct 19. pii: bjophthalmol-2017-310282. doi: 10.1136/bjophthalmol-2017-310282. [Epub ahead of print].

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