The influence of accommodation and vergence coupling during visual development.

Seemiller, Eric; Teel, Danielle F. W.; Babinsky, Erin; Roberts, Tawna L; Candy, T. Rowan

doi:10.1167/12.9.477

Cited by 2 publications

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“…The two ratios are inversely, 12 or reciprocally, related. 1,6,13-15 High AC/A accompanies low CA/C; if blur drives a large amount of convergence, then disparity drives less accommodation. In our laboratory, higher CA/C than AC/A ratios are typical.…”

Section: Why Ac/a and Ca/c Ratios Are Insufficientmentioning

confidence: 99%

Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus

Horwood

Riddell

2014

Journal of American Association for Pediatric Ophthalmology and

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PurposeTo propose an alternative and practical model to conceptualize clinical patterns of concomitant intermittent strabismus, heterophoria, and convergence and accommodation anomalies.MethodsDespite identical ratios, there can be a disparity- or blur-biased “style” in three hypothetical scenarios: normal; high ratio of accommodative convergence to accommodation (AC/A) and low ratio of convergence accommodation to convergence (CA/C); low AC/A and high CA/C. We calculated disparity bias indices (DBI) to reflect these biases and provide early objective data from small illustrative clinical groups that fit these styles.ResultsNormal adults (n = 56) and children (n = 24) showed disparity bias (adult DBI 0.43 [95% CI, 0.50-0.36], child DBI 0.20 [95% CI, 0.31-0.07]; P = 0.001). Accommodative esotropia (n = 3) showed less disparity-bias (DBI 0.03). In the high AC/A–low CA/C scenario, early presbyopia (n = 22) showed mean DBI of 0.17 (95% CI, 0.28-0.06), compared to DBI of −0.31 in convergence excess esotropia (n=8). In the low AC/A–high CA/C scenario near exotropia (n = 17) showed mean DBI of 0.27. DBI ranged between 1.25 and −1.67.ConclusionsEstablishing disparity or blur bias adds to AC/A and CA/C ratios to explain clinical patterns. Excessive bias or inflexibility in near-cue use increases risk of clinical problems.

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Section: Why Ac/a and Ca/c Ratios Are Insufficientmentioning

confidence: 99%

Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus

Horwood

Riddell

2014

Journal of American Association for Pediatric Ophthalmology and

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“…Although it is generally accepted that, in an individual, CA/C and AC/A ratios exist in broadly inverse or reciprocal relationships (with a high AC/A accompanying a low CA/C, and vice versa [12][13][14][15][16][17] ), this concept does not convey much meaning. It may be slightly easier if it is re-phrased as 'if someone drives their vergence from blur, they don't drive accommodation as much from disparity'.…”

Section: Introductionmentioning

confidence: 99%

Convergence accommodation in orthoptic practice

Horwood

2016

British and Irish Orthoptic Journal

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Aim: Orthoptists are familiar with AC/A ratios and the concept that accommodation drives convergence, but the reverse relationship, that of the accommodation associated with convergence, is rarely considered. Methods: This article reviews published evidence from our laboratory which has investigated the drives to both vergence and accommodation. All studies involved a method by which accommodation and vergence were measured concurrently and objectively to a range of visual stimuli which manipulate blur, disparity and proximal/looming cues in different combinations. Results: Results are summarised for both typical and atypical participants, and over development between birth and adulthood. Conclusions: For the majority of typical children and adults, as well as patients with most heterophorias and intermittent exotropia, disparity is the main cue to both vergence and accommodation. Thus the convergence fiaccommodation relationship is more influential than that of accommodative vergence. Differences in 'style' of near cue use may be a more useful way to think about responses to stimuli moving in depth, and their consequences for orthoptic patients, than either AC/A or CA/C ratios. The implications of a strong role for vergence accommodation in orthoptic practice are considered.

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The influence of accommodation and vergence coupling during visual development.

Cited by 2 publications

References 0 publications

Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus

Disparity-driven vs blur-driven models of accommodation and convergence in binocular vision and intermittent strabismus

Convergence accommodation in orthoptic practice

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