Content development of the Optometric Patient Anxiety Scale

Patient anxiety has been shown to be detrimental to many aspects of healthcare outcomes. To date, there is no method of evaluating anxiety in optometric practice. Therefore, the purpose of this study was the content development of a questionnaire to measure optometric patient anxiety. Such a tool will have both clinical and research application; allowing the identification of anxious patients in practice and as a method to establish the success of anxiety reducing interventions.

Selection of initial items was based on patient interviews, literature review, and focus group feedback. The initial 30-item Optometric Patient Anxiety Scale was piloted on 148 patients in optometric practice. Rasch analysis was used to analyze response category operation and to facilitate item removal to ensure a valid and unidimensional scale. Test-retest reliability (test-retest time, 2 weeks) was measured on 59 young adults to test the stability of the measure with time.

Rasch analysis identified disordering of category thresholds and underutilization of the end-response category. Therefore, categories were merged to a three response solution. Item reduction was principally driven by infit and outfit statistics. The items in the final 10-item scale all had good infit and outfit values (infit: 0.80-1.20, outfit: 0.7-1.3), good person separation (>2) and high person and item reliability coefficients, 0.84 and 0.88, respectively. Test-retest reliability also demonstrated good stability of the measure with time (intraclass correlation; ICC = 0.85).

The Optometric Patient Anxiety Scale is the first questionnaire to measure patient anxiety specific to optometric practice. The scale was developed using Rasch analysis to ensure that all the items work together to form a valid unidimensional interval scale.