CISS Score Alone May Not Be Suitable For Diagnosing Convergence Excess

Using Convergence Insufficiency Symptom Survey (CISS) scores may not be suitable for diagnosing convergence excess in adults, according to a study published in Ophthalmic and Physiological Optics. However, it may adequately measure symptoms in individuals with the disorder who have been identified based on clinical measurements, the report suggests. 

Researchers included second-year optometry students (n=181; mean age, 24.3 years; 72.9% women) at the Illinois College of Optometry in the cross-sectional study and performed cover, near point of convergence, fusional vergence, and accommodative amplitude tests. The team stratified participants into groups based on their binocular vision, which included individuals with normal binocular vision (group 1; n=96), participants with convergence excess (group 2; n=66), and patients with both convergence excess and accommodative insufficiency (group 3; n=19). The investigators assessed CISS score in all participants and used receiver-operating characteristic (ROC) curves to evaluate the survey instrument’s ability to discriminate convergence excess from normal binocular vision.

Compared with group 1 participants, group 2 individuals had significantly different heterophoria at distance (mean difference [MD], -0.4 Δ; P =.02), heterophoria at near (MD, -7.3 Δ; P =.01), negative fusional vergence (FV) break at near (MD, 4.6 Δ; P =.01), negative FV recovery at near (MD, 2.8 Δ; P <.001), and positive FV break at near (MD, -6.3 Δ; P =.002) measurements. For group 3 participants, significant differences from group 1 individuals were observed for heterophoria at near (MD, -8.5 Δ; P =.01), negative FV break at near (MD, 4.4 Δ; P =.01), negative FV recovery at near (MD, 3.9 Δ; P =.002), positive FV break at near (MD, -6.9 Δ; P =.049), and accommodation amplitude (MD, 2.3 OD; P <.001) parameters.

Among groups 2 and 3, group differences in heterophoria distance (MD, 0.6 Δ; P =.04) and accommodation amplitude (MD, 2.8 OD; P <.001) were noted.

The mean [SD] CISS scores were 12.2 [7.8], 16.7 [10.6], and 19.7 [10.9] (P <.001) among groups 1, 2, and 3, respectively. In pairwise comparisons, CISS scores were significantly higher among group 2 (MD, -4.1 points; P =.01) and group 3 (MD, -8.0 points; P =.005) compared with group 1, but significant group differences were not observed between groups 2 and 3 (MD, -3.9 points; P =.33).

In the ROC curve analysis, CISS score was able to differentiate convergence excess from normal binocular vision (area under the curve [AUC], 0.62; 95% CI, 0.53-0.71; P =.01). The best cutoff CISS value for differentiating between the two groups was 16 points (sensitivity, 0.52; specificity, 0.71).

These findings demonstrate that individuals with convergence excess had higher CISS scores compared with individuals with normal binocular vision, but failed to substantiate the use of CISS score alone for convergence excess diagnosis. When clinical measurements have identified convergence excess, the report shows that the CISS may prove useful as a tool for measuring symptoms.  

“The CISS can be used to provide a measure of symptoms in young adults identified as having [convergence excess] based on standard clinical parameters,” according to the researchers. “Furthermore, the CISS could potentially be used to quantify treatment outcomes in young adults with [convergence excess].”

Study limitations include the single center design and use of convenience sampling.