The Effect of Lens-Induced Anisometropia on Accommodation and Vergence during Human Visual Development

Candy, T. Rowan

doi:10.1167/iovs.10-6214

Cited by 23 publications

(15 citation statements)

References 56 publications

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“…Phillips studied eighteen, 11-year-old myopic children who wore a monovision spectacle correction over a 30 month period. Although participant numbers are small and though it contained only myopes, this study tentatively suggests that anisometropes may habitually focus the less ametropic eye, generating chronic defocus in the more ametropic eye (also see Bharadwaj and Candy, 2011). Consistent with this observation, amblyopia is generally found in the more ametropic eye of both anisohyperopes and anisomyopes (Rutstein and Corliss, 2004).…”

Section: Cause and Effect: A Classic Chicken And Egg Storymentioning

confidence: 70%

“…First, accommodation must remain yoked in the two eyes as unequal or uncoupled accommodation responses could theoretically bring both retinal images into focus. Most studies (Ball, 1952; Flitcroft et al, 1992; Koh and Charman, 1998; Bharadwaj and Candy, 2011; but see Horwood and Riddell, 2010) find that accommodation is consensual in the presence of anisometropia but small amounts of aniso-accommodation have been reported by Marran and Schor (1998, 1999), which may reflect the need for small amounts of aniso-accommodation with eccentric gaze (Charman, 2011). Second, for anisometropia to generate chronic defocus in one eye, anisometropes must habitually focus the other eye.…”

Section: Cause and Effect: A Classic Chicken And Egg Storymentioning

confidence: 99%

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The relationship between anisometropia and amblyopia

Barrett

Bradley

Candy

2013

Progress in Retinal and Eye Research

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143

121

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This review aims to disentangle cause and effect in the relationship between anisometropia and amblyopia. Specifically, we examine the literature for evidence to support different possible developmental sequences that could ultimately lead to the presentation of both conditions. The prevalence of anisometropia is around 20% for an inter-ocular difference of 0.5D or greater in spherical equivalent refraction, falling to 2-3%, for an inter-ocular difference of 3D or above. Anisometropia prevalence is relatively high in the weeks following birth, in the teenage years coinciding with the onset of myopia and, most notably, in older adults starting after the onset of presbyopia. It has about one-third the prevalence of bilateral refractive errors of the same magnitude. Importantly, the prevalence of anisometropia is higher in highly ametropic groups, suggesting that emmetropization failures underlying ametropia and anisometropia may be similar. Amblyopia is present in 1-3% of humans and around one-half to two-thirds of amblyopes have anisometropia either alone or in combination with strabismus. The frequent co-existence of amblyopia and anisometropia at a child’s first clinical examination promotes the belief that the anisometropia has caused the amblyopia, as has been demonstrated in animal models of the condition. In reviewing the human and monkey literature however it is clear that there are additional paths beyond this classic hypothesis to the co-occurrence of anisometropia and amblyopia. For example, after amblyopia secondary to either deprivation or strabismus has emerged, anisometropia often follows. In cases of anisometropia with no apparent deprivation or strabismus, questions remain about the failure of the emmetropization mechanism that routinely eliminates infantile anisometropia. Also, the chronology of amblyopia development is poorly documented in cases of ‘pure’ anisometropic amblyopia. Although indirect, the therapeutic impact of refractive correction on anisometropic amblyopia provides strong support for the hypothesis that the anisometropia caused the amblyopia. Direct evidence for the aetiology of anisometropic amblyopia will require longitudinal tracking of at-risk infants, which poses numerous methodological challenges. However, if we are to prevent this condition, we must understand the factors that cause it to develop.

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Section: Cause and Effect: A Classic Chicken And Egg Storymentioning

confidence: 70%

Section: Cause and Effect: A Classic Chicken And Egg Storymentioning

confidence: 99%

The relationship between anisometropia and amblyopia

Barrett

Bradley

Candy

2013

Progress in Retinal and Eye Research

Self Cite

143

121

View full text Add to dashboard Cite

show abstract

“…Banks et al . reported that altered retinal image size influences ocular dominance status during asymmetric convergence from the mid‐sagittal plane, however, Bharadwaj and Candy observed that lens induced aniseikonia up to 11% did not influence accommodation or vergence in adults. Since the dominant eye displayed a small but significantly greater accommodative response under binocular viewing conditions (with symmetrical vergence demands) irrespective of which eye received the monocular defocus, it is unlikely that the induced aniseikonia significantly influenced the results of this study.…”

Section: Discussionmentioning

confidence: 99%

The short‐term accommodation response to aniso‐accommodative stimuli in isometropia

Vincent

Collins

Read

et al. 2015

Ophthalmic Physiologic Optic

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“…The response can be a purposeful suppression of one image while accommodating on the other; this might be a very difficult binocular task for children. In typically developing children (3.1 months to 12.1 years) induced aniseikonia (by placing a 11% afocal magnifier to the right eye) did not significantly influence the gain of accommodation and vergence ( Bharadwaj and Candy, 2011 ), but the effect of aniseikonia on visually impaired children is still unclear. Magnifier use was compared to enlarged print ( Huurneman et al, 2013 ), but in this static task there was no cue conflict between the two eyes because they used a large dome magnifier enabling children to look at the symbols binocularly and perception of the surroundings was not relevant.…”

Section: Discussionmentioning

confidence: 99%

Effective and Efficient Stand Magnifier Use in Visually Impaired Children

et al. 2016

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Purpose: The main objective of this study was to analyze the effectiveness and efficiency of magnifier use in children with visual impairment who did not use a low vision aid earlier, in an ecologically valid goal-directed perceptuomotor task.Methods: Participants were twenty-nine 4- to 8-year-old children with visual impairment and 47 age-matched children with normal vision. After seeing a first symbol (an Lea Hyvärinen [LH] symbol), children were instructed to (1) move the stand magnifier as quickly as possible toward a small target symbol (another LH symbol that could only be seen by using the magnifier), (2) compare the two symbols, and (3) move the magnifier to one of two response areas to indicate whether the two symbols were identical. Performance was measured in terms of accuracy, response time, identification time, and movement time. Viewing distance, as well as hand and eye dominance while using the magnifier was assessed.Results: There were no significant differences between the two groups in accuracy, reaction time, and movement time. Contrary to the prediction, children with visual impairment required less time to identify small symbols than children with normal vision. Both within-subject and between-subject variability in viewing distance were smaller in the visually impaired group than in the normally sighted group. In the visually impaired group, a larger viewing distance was associated with shorter identification time, which in turn was associated with higher accuracy. In the normally sighted group, a faster movement with the magnifier and a faster identification were associated with increasing age.Conclusion: The findings indicate that children with visual impairment can use the stand magnifier adequately and efficiently. The normally sighted children show an age-related development in movement time and identification time and show more variability in viewing distance, which is not found in visually impaired children. Visually impaired children seem to choose a standard but less adaptive strategy in which they primarily used their preferred hand to manipulate the magnifier and their preferred eye to identify the symbol.Trial registration: Registered at http://www.trialregister.nl; NTR2380

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The Effect of Lens-Induced Anisometropia on Accommodation and Vergence during Human Visual Development

Cited by 23 publications

References 56 publications

The relationship between anisometropia and amblyopia

The relationship between anisometropia and amblyopia

The short‐term accommodation response to aniso‐accommodative stimuli in isometropia

Effective and Efficient Stand Magnifier Use in Visually Impaired Children

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