RT Journal Article
A1 Adeyemo, Olukemi
A1 Maeng, Meesa
A1 Szlyk, Janet P
A1 Dagnelie, Gislin
T1 Comparing person and item measures of the 150-item Ultra-low Vision Visual Functioning Questionnaire (ULV-VFQ) from two separate ULV populations
JF Investigative Ophthalmology & Visual Science
JO Invest. Ophthalmol. Vis. Sci.
YR 2019
VO 60
IS 9
SP 4966
OP 4966
SN 1552-5783
AB    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.    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.    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.    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. 
RD 1/23/2021