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Validity and Reliability of the Glaucoma Knowledge Level Questionnaire
Zeynep Demirtaş1, Gökçe Dağtekin1, Muhammed Fatih Önsüz1
1Eskişehir Osmangazi University Faculty of Medicine, Department of Public Health, Eskişehir, Turkey.
Turkish Journal of Ophthalmology
|July 11, 2018
Summary
A new 10-item questionnaire effectively measures glaucoma knowledge in adults. This valid and reliable instrument is the first of its kind in Turkey, aiding in assessing public understanding of the eye condition.
Area of Science:
- Ophthalmology
- Public Health
- Psychometrics
Background:
- Glaucoma is a leading cause of irreversible blindness worldwide.
- Assessing public knowledge is crucial for early detection and prevention strategies.
- Existing instruments may not be suitable for all populations or may lack robust validation.
Purpose of the Study:
- To develop and validate a reliable instrument for measuring glaucoma knowledge in adults.
- To establish the psychometric properties of the newly developed glaucoma knowledge questionnaire.
- To provide a culturally relevant tool for assessing glaucoma awareness in Turkey.
Main Methods:
- Development of a 27-item questionnaire by a study team.
- Expert review and structural evaluation of the questionnaire items.
- Calculation of difficulty and discrimination indices for item analysis.
- Factor analysis (exploratory and confirmatory) for construct validity and scale fit.
- Reliability assessment using Cronbach's alpha and item-total correlations.
- Correlation analysis with the National Eye Health Education Program (NEHEP) Eye-Q scale for concurrent validity.
Main Results:
- A 10-item, one-dimensional glaucoma knowledge questionnaire was finalized.
- Item analysis indicated appropriate difficulty (33-61%) and discrimination (0.28-0.65) indices.
- Factor analysis confirmed construct validity (Kaiser-Meyer-Olkin = 0.760, p<0.001).
- Confirmatory factor analysis demonstrated acceptable model fit.
- The questionnaire showed a significant positive correlation with the NEHEP Eye-Q scale (r=0.522, p<0.001).
- Higher knowledge scores were observed in younger participants (40-64), urban dwellers, those with higher education, and individuals with prior eye examinations or intraocular pressure measurements.
Conclusions:
- The developed 10-item questionnaire is a valid and reliable tool for assessing adult glaucoma knowledge.
- This instrument represents the first validated scale for measuring glaucoma knowledge in Turkey.
- The findings highlight demographic factors associated with higher glaucoma awareness, informing targeted health education initiatives.
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