Purchase this article with an account.
J. Felius, A.S. Lloyd, E.E. Birch; Co–maturation of Convergence and Accommodation Responses With Contrast Sensitivity and Binocular Vision . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2926.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Abnormalities in the link between convergence and accommodation, as assessed by the 'response AC/A ratio' may play an important role in the pathogenesis of accommodative eye misalignment in pediatric patients. Identifying such abnormalities during infancy is hampered by the simultaneous (normal) maturation of those aspects of visual function: stereoacuity and contrast sensitivity, which presumably drive convergence and accommodation. Here we studied the normal courses of maturation of convergence, accommodation and visual function within the same subjects. Methods: Convergence and accommodation responses (simultaneously measured using a PowerRefractor), sweep–VEP contrast sensitivity, and stereoacuity (Randot Stereocards) were studied in 16 infants (enrolled at 2.8 +/– 1.1 months of age) on multiple (median = 3) visits during the first year of life. The convergence response was quantified by evaluating the change in eye alignment for varying target distances (0.25 – 1.0 meter). The change in refractive state defined the accommodation response to these targets. Results: Different rates of maturation were found for these measures, especially prior to age 6 months, while all exhibited a more similar and slower development thereafter. The convergence response and stereoacuity showed the most drastic changes (0.37 and 0.10 log units/month, respectively) before 6 months, while accommodation and peak contrast sensitivity (0.02 and 0.05 log units/month, respectively) developed more slowly. As a result, the normal response AC/A ratio varied from 1.0 at age 2 months to 2.0 at age 6 months and remained approximately constant during the remainder of follow–up. Conclusions: These differences in the rates of maturation support the notion that convergence is driven by stereoacuity and accommodation is driven by contrast sensitivity. Variations among the time courses of maturation for convergence and accommodation must be kept in mind when utilizing AC/A ratio information obtained from infants.
This PDF is available to Subscribers Only