July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Comparing person and item measures of the 150-item Ultra-low Vision Visual Functioning Questionnaire (ULV-VFQ) from two separate ULV populations
Author Affiliations & Notes
  • Olukemi Adeyemo
    Johns Hopkins University, Baltimore, Maryland, United States
  • Meesa Maeng
    The Chicago LightHouse for People Who Are Blind or Visually Impaired, Chicago, Illinois, United States
  • Janet P Szlyk
    The Chicago LightHouse for People Who Are Blind or Visually Impaired, Chicago, Illinois, United States
    Jesse Brown VA Medical Center, Chicago, Illinois, United States
  • Gislin Dagnelie
    Johns Hopkins University, Baltimore, Maryland, United States
  • Footnotes
    Commercial Relationships   Olukemi Adeyemo, None; Meesa Maeng, None; Janet Szlyk, None; Gislin Dagnelie, Johns Hopkins University (P)
  • Footnotes
    Support  NIH, R01EY028452
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4966. doi:
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      Olukemi Adeyemo, Meesa Maeng, Janet P Szlyk, Gislin Dagnelie; Comparing person and item measures of the 150-item Ultra-low Vision Visual Functioning Questionnaire (ULV-VFQ) from two separate ULV populations. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4966.

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

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Abstract

Purpose : We have previously published ULV-VFQ item measures calibrated in an 80-person sample (Jeter, TVST 6:11, 2017). Here we compare the earlier calibration with measures obtained in a separate ULV population.


Methods : Responses from 45 subjects at the Chicago Lighthouse were obtained and Rasch-analyzed in Winsteps©, in 3 separate models: 1) Using the item and response structure from the original calibration to anchor the analysis; 2) Separately analyzing the CLH data set without anchoring; and 3) Analyzing the combined data set. Correlations and fit statistics were calculated.

Results : The item-measure distribution of the ULV questionnaire items ranged from -4.01 (less difficult to complete) to + 3.54(more difficult to complete) for the 80-subject (JHU) sample. For the 45-subject (CLH) sample, item measures were between -2.70 to +3.39. The difference in range was due to a few outliers, however: RMS spreads of the item measure distribution were very similar: JHU 1.23, CLH 1.18. Correlation between items is 0.84. The person measures ranged from -3.24 to 6.10 with anchoring; -3.17 to 6.23 without anchoring. Correlation between the free and anchored person measures is 0.999. Rasch analysis was repeated for the combined data set, and differential item functioning was found for only a single item. Person and item reliability coefficients for the combined analysis were .99 and .98, respectively. Item measure correlation between the CLH and full sample were .935, and item measure spread and range corresponded more closely, as expected.


Conclusions : Our data shows strong reliability of the ULV-VFQ’s item and person measures and highly correlated item measures for both populations. This supports the notion that the ULV-VFQ as currently calibrated is a highly reliable measure of functional vision in individuals with ULV.


This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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