Purpose: To assess the validity and reliability of the revised Convergence Insufficiency Symptom Survey (CISS) in adults aged 19-30 years. The CISS was developed to be the primary outcome measure for studies evaluating various treatments for convergence insufficiency (CI).
Methods: CISS mean scores from adults with symptomatic CI and adults with normal binocular vision (NBV) were compared to assess the survey's validity. Adults with symptomatic CI were given the CISS twice to evaluate reliability, which was assessed using intraclass correlation coefficient (ICC) and 95% limits of agreement.
Results: Forty-six adults with CI and 46 adults with NBV participated in the study. The mean CISS score for the CI group was 37.3 (S.D. = 9.3) and 11.0 (S.D. = 8.2) for the NBV group. These mean values were significantly different (p < 0.0001). Good discrimination (sensitivity = 97.8%, specificity = 87%) was obtained using a score of 21 or higher. For the CI group the ICC was 0.885 (95% CI of 0.798, 0.936) and the 95% limits of agreement were -9.0 to 7.6.
Conclusions: Adults with symptomatic CI had a significantly higher CISS score than adults with NBV. The results of the study demonstrate that the CISS is a valid and reliable instrument that can be used clinically or as an outcome measure for research studies of adults with CI.