Purpose. Accommodative insufficiency (AI) and convergence insufficiency (CI) have been associated with similar symptomology and frequently present at the same time. The severity of symptomology in CI has been linked to the severity of the CI, suggesting a dose-dependent relationship. However, with increasing severity of CI also comes increased comorbidity of AI. AI alone has been shown to cause significant symptomology. We hypothesize that AI drives the symptoms in CI with a comorbid AI condition (CIwAI) and that it is the increased coincidence of AI, rather than increased severity of CI, which causes additional symptomology.
Methods. Elementary school children (n = 299) participated in a vision screening that included tests for CI and AI and the CISS-V15 symptom survey. They were categorized into four groups:1) normal binocular vision (NBV); 2) AI-only; 3) CI-only; and 4) CIwAI. One hundred seventy elementary school children fell into the categories of interest.
Results. Pairwise comparison of the group means on the symptom survey showed: 1) children with AI-only (mean = 19.7, p = 0.006) and children with CIwAI (mean = 22.8, p = 0.001) had significantly higher symptom scores than children with NBV (mean = 10.3); and 2) children with CI-only (mean = 12.9, p = 0.54) had a similar symptom score to children with NBV. Using a two-factor analysis of variance (AI and CI), the AI effect was significant (AI mean = 21.56; no AI mean = 11.56, p < 0.001), whereas neither the CI effect (p = 0.16) nor the CI by AI interaction effect (p = 0.66) were significant.
Conclusion. CI is a separate and unique clinical condition and can occur without a comorbid AI condition, our CI-only group. Past reports of high symptom scores for children with CI are the result of the presence of AI, a common comorbid condition. When AI is factored out, and children with CI only are evaluated, they are not significantly more symptomatic than children with NBV.