July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Calibration of the Impact of Vision Impairment Instrument (IVI) Questionnaire
Author Affiliations & Notes
  • Judith Goldstein
    Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States
  • Eva Fenwick
    Population Health, Singapore Eye Research Institute, Singapore, Singapore
    Duke-NUS Medical School, Singapore, Singapore
  • Robert Patrick Finger
    University of Bonn, Bonn, Germany
  • Vijaya Gothwal
    Patient Reported Ouctomes Unit, L V Prasad Eye Institute-Brien Holden Eye Resarch Centre, Hyderabad, India
    Centre for Sight Enhancement-Meera and L B Deshpande, L V Prasad Eye Institute, Hyderabad, India
  • Mary Lou Jackson
    Ophthalmology, Vancouver General Hospital/University of British Columbia, Vancouver, British Columbia, Canada
  • Ecosse Luc Lamoureux
    Population Health, Singapore Eye Research Institute, Singapore, Singapore
    Duke-NUS Medical School, Singapore, Singapore
  • Gwyneth Rees
    Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne,, Victoria, Australia
    Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
  • Robert W Massof
    Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States
  • Footnotes
    Commercial Relationships   Judith Goldstein, None; Eva Fenwick, None; Robert Finger, None; Vijaya Gothwal, None; Mary Lou Jackson, None; Ecosse Lamoureux, None; Gwyneth Rees, None; Robert Massof, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 3913. doi:
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    • Get Citation

      Judith Goldstein, Eva Fenwick, Robert Patrick Finger, Vijaya Gothwal, Mary Lou Jackson, Ecosse Luc Lamoureux, Gwyneth Rees, Robert W Massof; Calibration of the Impact of Vision Impairment Instrument (IVI) Questionnaire. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3913.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose : Provide calibrated item estimates for the Impact of Vision Impairment instrument (IVI) to improve uniformity in measurement across studies. Working collaboratively and pooling data, our aim is to maximize precision in these item estimates, such that they can function as an item bank. This item bank will be available to researchers and clinicians to support measurement of visual ability in people with vision impairment.

Methods : Eight datasets from 6 principal investigators representing responses to IVI items from 2867 low vision patients were pooled for analysis. Eligible patients were ≥18 years and from Australia, India, and the United States. Data from each sample included raw scores of patient responses to the IVI, visual acuity (VA), ocular diagnosis, date of birth or age, and sex. Rasch analysis, using the Andrich Rating Scale Model (Winsteps ver 3.65), was performed on pre-intervention IVI responses to estimate person and item reliability, item measures and response category thresholds, and a set of person measures for each patient. “Emotional Well-being” (8 items) were excluded in the estimates of the person measures as Lamoureux, et al., have shown that these items represent a separate measure. Differential item functioning (DIF) by patient sample was evaluated.

Results : Patients ranged in age from 18 to 103 years with a median age of 62, with males representing 55% of the sample. Macular degeneration was the primary diagnosis in 29% of all patients, while the residual represented all other ocular disorders. Visual ability as estimated by person measures from the IVI scaled monotonically with VA. Mean person measures for patients ≥20/40 (n=414) were 0.51 (SD 1.11), 0.16 (SD 1.04) for patients <20/40 to 20/60 (n=467), 0.09 (SD 0.96) for patients <20/60 to 20/200 (n=984) and -0.23 (SD 0.92) for patients <20/200 (n=995); VA was missing in 7 patients. There were indications of non-uniform DIF in one dataset. In examining covariates, this dataset contained subjects that were younger and had worse visual acuity than patients in the other datasets.

Conclusions : Item difficulty estimates from a varied dataset of people with visual impairment supports the ability to calibrate IVI measures and shows minimal non-uniform DIF. This item bank may be used by researchers and clinicians for comparative estimates of functional ability in a common unit of measurement when studying baseline traits or treatment outcomes.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.


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