Association of fusional convergence and divergence with control ability in children with intermittent exotropia

Background

Intermittent exotropia is a type of strabismus that between latent extropia and manifest extropia.The assessment of fusional convergence/divergence is important for understanding control ability of exodeviation in children with intermittent exotropia.

Objective

This study was to analyze the correlations between fusional convergence/divergence and control ability of exodeviation in children with intermittent exotropia.

Methods

Sixty-three children with intermittent exotropia were recruited in Beijing Tongren Eye Centre from July 2013 to February 2014 under the informed consent of children and their parents.Angle of deviation was measured by wearing prism and covering method alternately.The control ability of exodeviation was evaluated and scored by the Revised Newcastle Control Score (RNCS), and fusional convergence and divergence were measured with 1^△-40^△horizonal prisms and regulating targets.The correlations between the measured parameters of fusional convergence/divergence and control scores of exotropia were analyzed by Spearman rank correlation analysis.

Results

The mean diopter of the right and left eyes was (-1.95±1.63)D and (-2.01±1.73)D, respectively, and the mean deviation angle for distantly and near was (36.67±15.69)^△and (38.25±14.83)^△, respectively, without significant differences between them (diopter: t=-0.13, P>0.05; deviation angle: t=-0.57, P>0.05). Considerably negative correlations were found between the breakpoints of fusional convergence for distant or near and control scores of exodeviation (r_s=-0.41, P=0.03; r_s=-0.56, P<0.01). No significant correlations were found between the breakpoints of fusional divergence for distantly or near and control scores of exodeviation (r_s=0.05, P=0.78; r_s=0.04, P <0.75). In addtion, there was no significant correlation between fusional recovery level and control scores (both at P>0.05).

Conclusions

Breakpoints of fusional convergence may be useful in grading the severity of intermittent exotropia in children, and it is probably one of the surgical indications of intermittent exotropia.