Vergence adaptation in children and its clinical significance.
OBJECTIVE
Vergence adaptation has not been well investigated in children even though it may contribute to binocular dysfunction and near work induced asthenopia.


METHODS
We compared vergence adaptation in 18 children and 18 young adult subjects by assessing tonic vergence (TV) before and immediately after a period of sustained near fixation, by measuring heterophoria with a synoptophore through 0.5 mm binocular pinholes. Adaptation was induced by a reading task at 15 cm for a continuous 5 minute period.


RESULTS
Mean pre-task TV values of 0.70 MA (Meter Angles) and 0.20 MA were observed for the children and young adults, respectively (p = 0.08). The initial mean vergence adaptation for children and adults was +0.45 MA and +0.11 MA, respectively (p = 0.001).


CONCLUSIONS
The greater vergence adaptation observed in children may impact upon the clinical assessment of their binocular vision, especially heterophoria measurement which may require longer periods of dissociation than previously recommended, and might also ultimately be partly responsible for the predominant development of esodeviations during childhood
State University of New York, State College of Optometry, New York, New York 10036, USA.
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D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003290:Convergence, Ocular / Q000502:physiology*; D006801:Humans; D009988:Orthoptics / Q000379:methods; D013285:Strabismus / Q000503:physiopathology*; D014787:Vision Tests; D015348:Vision, Binocular / Q000502:physiology*