A Vision Quality of Life Questionnaire that combines the SF-20 and a V
ision Quality Scale developed by the authors was pilot tested in a cas
e-comparison of extreme groups, patients with intermittent exotropia (
IXT) and those with no vision problems (Non-IXT), at the University of
Houston (UH) Optometry Clinic, The purposes of the study were to meas
ure the internal consistency reliability and examine the validity-rela
ted evidence of vision function associated with the instrument, The pi
lot study involved mailing the instrument to 52 patients in each group
(IXT and Non-IXT patients), IXT patients were then frequency-matched
by age and separately by sex, to control for confounding variables, to
Non-IXT group patients, The Cronbach's Alpha internal consistency rel
iability of both scales was acceptable at >0.70 for both the IXT and N
on-IXT groups, The Wilcoxon signed ranks test was used to determine va
lidity-related evidence, The differences between groups on the SF-20 (
p = 0.0276) and Vision Function Scale (VFS) (p = 0.0385) confirm that
the scales discriminate between IXT and Non-IXT populations, Two concl
usions can be drawn from the pretesting and pilot testing of the SF-20
and the VFS: (1) both have acceptable internal consistency reliabilit
y scores, and (2) both show validity-related evidence that they can di
scriminate vision function between IXT and Non-IXT patient populations
.