Optometry Research Today is a free monthly online journal that collates and summarizes the latest research about Optometry, including details on myopia, optometric practice, therapy.

The Refractive Status and Vision Profile: evaluation of psychometric properties and comparison of Rasch and summated Likert-scaling.

Garamendi E, Pesudovs K, Stevens MJ, Elliott DB

Department of Optometry, University of Bradford, Richmond Road, Bradford, West Yorkshire, BD7 1DP, United Kingdom.

The psychometric properties of the Refractive Status and Vision Profile (RSVP) questionnaire were evaluated using Rasch analysis. Ninety-one myopic patients from a refractive surgery clinic and general optometric practice completed the RSVP. Rasch analysis of the RSVP ordinal data was performed to examine for unidimensionality and item reduction. The traditional Likert-scoring system was compared with a Rasch-scored RSVP and a reduced item Rasch-scored RSVP. Rasch analysis of the original RSVP showed poor targeting of item difficulty to patient quality of life, items with a ceiling effect and underutilized response categories. Combining the underutilized response scales and removal of redundant and misfitting items improved the internal consistency and targeting of the RSVP, and the reduced 20-item Rasch scored RSVP showed greater relative precision over standard Likert scoring in discriminating between the two subject groups. A Rasch scaled quality of life questionnaire is recommended for use in refractive outcomes research.

Published 17 January 2006 in Vision Res, 46(8): 1375-83.
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