Psychometric properties of the 25-item NEI-VFQ in a Hispanic population: Proyecto VER.

PURPOSE: To assess the psychometric properties of the NEI-VFQ-25 in a population-based study of older Hispanic persons living in the United States, explore other demographic factors that affect participant response, and observe the comparability of the Spanish and English versions of the instrument.

METHODS: A sample of randomly selected block groups in Tucson and Nogales, Arizona, were selected for study. Participants were interviewed at home; a majority of the interviews were conducted in Spanish. The home interview included questions from the NEI-VFQ-25 and HHANES: Presenting acuity was done using ETDRS methodology, followed by a standardized eye examination by an ophthalmologist. The authors analyzed the internal consistency of the NEI-VFQ-25 responses using Cronbach's alpha coefficient and the construct validity by assessing the relationship between presenting acuity and scale scores, adjusting for age and gender. A second model was also explored to determine whether other demographic variables affected scale scores; differences in reporting between the Spanish and English versions was observed in this model, used in a subset of the population that minimized interviewer effect.

RESULTS: Of the 4774 participants in the study, 99.7% had completed questionnaires, not completed by proxy. The highest nonresponse rate occurred in the Driving scale, with 25% of participants not driving for reasons other than problems with vision. Internal consistency was high, with Cronbach alpha ranging between 0.65 and 0.86 for scales with multiple items. Adjusting for age and gender, those with presenting acuity worse than 20/40 scored significantly lower than those with presenting acuity 20/40 or better, for all scales. The demographic variables with the most consistent association across the NEI-VFQ-25 scales were presenting acuity, income, and gender. No significant differences in reporting were found between the Spanish and English versions of the questionnaire in the subset of the population.

CONCLUSIONS: In this study of Hispanic people age 40 years or older, the NEI-VFQ-25 was sensitive to presenting acuity and other demographic variables, such as age, gender, and income. The findings from this psychometric analysis provide evidence of the reliability and validity of some of the scales in the 25-item NEI-VFQ when used among people with a range of visual acuity level, providing other explanatory variables are also considered.