Abstract
Abstract: :
Purpose: Questionnaires are an essential tool in the subjective assessment of dry eye. Some dry eye questionnaires have made use of category–based questions whilst others have used visual analogue scales (VAS). This study compares the results obtained with both of these types of questionnaire when used on the same population. Methods: Ten questions relating to dry eye symptoms were taken from commonly used and validated dry eye questionnaires. Using these 10 questions two questionnaires were constructed. One version required the respondent to answer the questions by choosing a suitable category of response. In the second version, respondents indicated their response by marking a vertical line, at a point of their choice, on a visual analogue scale (VAS) that ranged from the two possible extreme responses to the question. The questionnaires were printed with one version on each side of a single piece of paper. The order of administration was random and the sequence of the individual questions was also randomised to avoid systematic bias. In addition, half of the VAS questionnaires were printed with indicator lines at 25, 50, and 75 % along the line to see if this altered the response, or the distribution, of the answers observed. Two hundred questionnaires were completed by members of the public (30% male, 70% female, mean age 29 years) who were approached in the street and requested to complete both sides of the questionnaire. Results: It was found that the order in which the two questionnaires were administered did not make a statistically significant difference in the responses obtained (Mann–Whitney U Test p > 0.05). Moreover, positive correlations were found between the answers to the VAS and the category type questions for all 10 questions (Spearman's rank correlation p < 0.05). An interesting point was that the distribution of the results obtained with VAS with indicator lines showed clusters of answers that coincided with the markers at 25, 50 and 75%. This was not apparent in the VAS with no indicators. Conclusions: Category based and VAS questionnaires give good agreement when used to assess dry eye symptomology. It is apparent, however, that when VAS questionnaires are used with indicator lines, the response is more akin to that seen with a categorical questionnaire.
Keywords: cornea: tears/tear film/dry eye • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • pathology: human