Elsevier

Vision Research

Volume 101, August 2014, Pages 51-61
Vision Research

Can current models of accommodation and vergence predict accommodative behavior in myopic children?

https://doi.org/10.1016/j.visres.2014.05.008Get rights and content
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Highlights

  • Accommodation (ACC) showed high adaptation, lag and ACC vergence in myopic children.

  • Vergence showed reduced adaptation but normal gain of convergence ACC in myopes.

  • This pattern would not be predicted from adult models of the near triad.

  • Reduced gain of the ACC plant (ciliary muscle and lens) might offer better prediction.

Abstract

Investigations into the progression of myopia in children have long considered the role of accommodation as a cause and solution. Myopic children show high levels of accommodative adaptation, coupled with accommodative lag and high response AC/A (accommodative convergence per diopter of accommodation). This pattern differs from that predicted by current models of interaction between accommodation and vergence, where weakened reflex responses and a high AC/A would be associated with a low not high levels of accommodative adaptation. However, studies of young myopes were limited to only part of the accommodative vergence synkinesis and the reciprocal components of vergence adaptation and convergence accommodation were not studied in tandem. Accordingly, we test the hypothesis that the accommodative behavior of myopic children is not predicted by current models and whether that departure is explained by differences in the accommodative plant of the myopic child. Responses to incongruent stimuli (−2D, +2D adds, 10 prism diopter base-out prism) were investigated in 28 myopic and 25 non-myopic children aged 7–15 years. Subjects were divided into phoria groups – exo, ortho and eso based upon their near phoria. The school aged myopes showed high levels of accommodative adaptation but with reduced accommodation and high AC/A. This pattern is not explained by current adult models and could reflect a sluggish gain of the accommodative plant (ciliary muscle and lens), changes in near triad innervation or both. Further, vergence adaptation showed a predictable reciprocal relationship with the high accommodative adaptation, suggesting that departures from adult models were limited to accommodation not vergence behavior.

Keywords

Accommodative adaptation
Vergence adaptation
Myopia
AC/A

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