Measuring binocular fusion in normal children:A comparison between the prism bar method and synoptophore method

Abstract

Objective To evaluate differences between the prism bar and synoptophore methods in the measurement of fusional convergence and fusional divergence in normal children. Methods This was a prospective research study. Children aged 8 to 15 years who had no ocular disease were recruited and tested with their prescribed refractions. The break and recovery points of fusional convergence and fusional divergence were measured by the prism bar and synoptophore methods respectively. Each test was repeated 3 times. An independent samples t-test was used to compare the difference between the 2 methods. Correlation between the two methods was analyzed by a Spearman rank correlation. Results There were no differences in break and recovery points of fusional vergences between dominant eye and non-dominant eye. There were positive correlations between break point values measured by the synoptophore and prism bar (convergence r=0.60,P<0.01; divergence r=0.46, P<0.05). When measured by the prism bar and synoptophore respectively, no significant differences could be found for either the values of the break points or that of recovery points of the 2 methods. Conclusion When measuring the distance fusional vergences, prism bar and synoptophore with similar effect. Key words: Fusional convergence; Fusional divergence; Synoptophore; Prism bar