You have full text access to this OnlineOpen article

Psychometric properties of visual functioning index using Rasch analysis

  1. Vijaya K. Gothwal1,2,
  2. Thomas Wright1,
  3. Ecosse L. Lamoureux3,4,5,
  4. Konrad Pesudovs1

Article first published online: 26 JUN 2009

DOI: 10.1111/j.1755-3768.2009.01562.x

Issue

Acta Ophthalmologica

Acta Ophthalmologica

Volume 88, Issue 7, pages 797–803, November 2010

Additional Information

How to Cite

Gothwal, V. K., Wright, T., Lamoureux, E. L. and Pesudovs, K. (2010), Psychometric properties of visual functioning index using Rasch analysis. Acta Ophthalmologica, 88: 797–803. doi: 10.1111/j.1755-3768.2009.01562.x

Author Information

  1. 1

    National Health and Medical Research Council Centre for Clinical Eye Research, Department of Ophthalmology, Flinders Medical Centre and Flinders University of South Australia, Adelaide, Australia

  2. 2

    Meera and L.B. Deshpande Centre for Sight Enhancement, Vision Rehabilitation Centres, L.V. Prasad Eye Institute, Hyderabad, India

  3. 3

    Centre for Eye Research Australia, The University of Melbourne, Melbourne, Australia

  4. 4

    Vision Cooperative Research Centre Limited, Sydney, Australia

  5. 5

    Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore

*Konrad Pesudovs NH & MRC Centre for Clinical Eye Research, Department of Ophthalmology Flinders Medical Centre Bedford Park South Australia 5042 Australia Tel: + 618 8204 4899 Fax: + 618 8277 0899 Email: konrad.pesudovs@flinders.edu.au

Publication History

  1. Issue published online: 26 JUN 2009
  2. Article first published online: 26 JUN 2009
  3. Received on November 18th, 2008. Accepted on January 29th, 2009.

SEARCH

SEARCH BY CITATION

ARTICLE TOOLS

View Full Article (HTML) Get PDF (247K)

Keywords:

  • cataract;
  • cataract surgery;
  • classical test theory;
  • Rasch analysis;
  • visual functioning index

Acta Ophthalmol. 2010: 88: 797–803

Abstract.

Purpose:  The visual functioning index (VFI) was one of the first questionnaires developed using classical test theory to assess outcomes of cataract surgery. However, it was not Rasch-validated. The objective of this study was to examine the psychometric properties of the VFI using Rasch analysis in patients with cataract.

Methods:  The 11-item VFI was self-administered to 243 patients (mean age 73.9 years) drawn from a cataract surgery waiting list. We examined the response category thresholds, item fit statistics, differential item functioning and unidimensionality for the VFI and its three subscales.

Results:  Category thresholds were ordered. The person separation and reliability were low, indicating the poor discriminatory ability of the VFI. No items misfit but there was suboptimal targeting of item difficulty to patient ability. On the whole the items in the VFI were too easy for the sample. Only one item showed moderate differential item functioning.

Conclusion:  The VFI does not meet the stringent requirements of the Rasch model. However adding more items to suit the more able patients with cataract as well as those awaiting second-eye cataract surgery could optimize the VFI.

View Full Article (HTML) Get PDF (247K)