Abstract
Binocular fusion requires binocular coordination. If fusion does not occur, input to the visual system may be degraded. Evidence shows that poor readers tend to have poor binocular coordination, but little is known about the nature of binocular fusion in adolescents, and less is known about the plasticity of fusional ranges in this age group. We examined optometric data from over 500 adolescents who were selected to participate in a visual skills training program at school because they were reading below grade level. Binocular fusion ranges were measured on each student with a vertical prism bar, for both convergence and divergence. Depending upon the criterion selected for “dysfunction,” 30–60% had binocular fusion ranges outside clinical norms for either convergence or divergence or both. Students who practiced vergence skills by fusing random dot stereograms in a 4-alternative-forced-choice paradigm for at least 20–30 sessions of 3 minutes per day improved binocular fusion ranges significantly. Although this study was retrospective, it suggests that (1) a relatively large number of adolescents who read poorly may exhibit poor binocular skills, and (2) fusional ranges are relatively plastic in adolescent students. More rigorous studies need to be done to determine the generalizability of these results.