Objectives: To evaluate the relationship of a performance-based measure of visual functioning to clinical and subjective measures in glaucoma patients.
Design: Cross-sectional survey of glaucoma patients.
Participants: Forty-three patients with primary open-angle glaucoma.
Methods: Patients were evaluated using a novel performance-based measure, the Assessment of Function Related to Vision (AFREV), standard clinical tests of visual function, and the National Eye Institute's Visual Functioning Questionnaire (NEI-VFQ-25), a self-reported quality of life measure. Correlations of the AFREV scores with visual field scores, monocular and binocular visual acuity, contrast sensitivity scores, and NEI-VFQ scores were calculated. Rasch analysis was used to estimate the visual ability required by each task of AFREV for a particular response (item measures) and to estimate the visual ability of each patient (person measures).
Main outcome measures: AFREV and NEI-VFQ total scores.
Results: The AFREV total scores were highly correlated with contrast sensitivity (r = 0.772), binocular visual acuity (r = -0.768), better-eye visual acuity (r = -0.737), worse-eye visual acuity (r = -0.675), and Estermann visual field efficiency scores (r = 0.606) as well as with NEI-VFQ scores (r = 0.70). The resulting index, constructed from 5 items of the AFREV, is unidimensional, thereby satisfying the primary assumption of the Rasch model. The Rasch person-item map demonstrates that the "putting stick into holes" and "reading small print" tests require the most visual ability.
Conclusions: The AFREV performance-based measure, a new test of a spectrum of activities, correlates well with some standard measures of visual function and certain aspects of self-report assessments. AFREV appears to be a valid measure of performance ability that may provide information not obtainable from standard measures of visual function or subjective surveys.