Development of a quality-of-life questionnaire for adults with strabismus

Abstract

Purpose: We report the development of a patient-derived, health-related quality-of-life (HRQOL) questionnaire for adults with strabismus.

Design: Cross-sectional study.

Participants: Twenty-nine patients with strabismus in a first phase, and 32 patients with strabismus, 18 patients with other eye diseases, and 13 visually normal adults in a second phase.

Methods: Individual patient interviews generated 181 questionnaire items. For item reduction, we asked 29 patients with strabismus to complete the 181-item questionnaire, analyzed responses, and performed factor analysis. Two prominent factors were identified, and the 10 items with the highest correlation with each factor were selected. The final 20-item questionnaire (10 psychosocial items and 10 function items) was administered to an additional 32 patients with strabismus (22 with diplopia, 10 without diplopia), 13 visually normal adults, and 18 patients with other eye diseases. A 5-point Likert-type scale was used for responses (never = 100, rarely = 75, sometimes = 50, often = 25, and always = 0). Median overall questionnaire scores and psychosocial and function subscale scores, ranging from 0 (worst HRQOL) to 100 (best HRQOL), were compared across groups.

Main outcome measures: The HRQOL questionnaire response scores.

Results: Median overall scores were statistically significantly lower (worse quality of life) for patients with strabismus (56) compared with visually normal adults (95; P<0.001) and patients with other eye diseases (86; P<0.001). Median scores on the psychosocial subscale were significantly lower for strabismus patients (69) compared with visually normal adults (99; P<0.001) and patients with other eye diseases (94; P<0.001). For the function subscale, median scores were again significantly lower for strabismus patients (43) compared with visually normal adults (91; P<0.001) and patients with other eye diseases (78; P<0.001).

Conclusions: We have developed a 20-item, patient-derived, HRQOL questionnaire specific for adults with strabismus, with subscales to assess psychosocial and function concerns. This 20-item, condition-specific questionnaire will be useful for assessing HRQOL in individual strabismus patients and also as an outcome measure for clinical trials.

Financial disclosure(s): The authors have no proprietary or commercial interest in any materials discussed in this article.

Figure 1

Scree plot showing eigen values for main factor analysis. Two strong factors are evident on the steep phase of the curve.

Figure 2

Overall, psychosocial subscale and function subscale health related quality of life (HRQOL) scores on the AS-20 for visually normal adults, patients with other eye diseases, and patients with strabismus. Scores are also shown separately for strabismus patients with and without diplopia. Medians are shown as the central line, quartiles as boxes, and extremes as whiskers.