Table 1.
Estimates of item parameters.
Table 2.
Candidate items, and the 11 items chosen (*) for the short version of the VFQ (the VFQ-J11).
Figure 1.
Targeting of item thresholds with regard to the patients in this study.
The Figure shows locations of the patients (above) and of the item thresholds (below) on the same scale, in units of the latent trait.
Figure 2.
Test information functions for the VFQ25 and the VFQ-J11.
Both functions reached their maxima at about the same value of the latent trait (a theta of approximately −0.8). For values of theta between approximately −2.0 and +0.8, the test information for the VFQ-J11 was greater than 9, which indicates that in that range (−2.0 to +0.8) the test's reliability is equivalent to or greater than a Cronbach's alpha of 0.9.
Table 3.
Scores on the VFQ25 and VFQ-J11 in patients with different eye diseases.
Table 4.
Correlations of scores on the VFQ25 and the VFQ-J11 with visual acuity and with visual field.