Purpose:
To evaluate the sensitivity of the Vision quality of life Core Measure (VCM1) and the Low Vision Quality Of Life questionnaire (LVQOL) to change vision related quality of life using the polytomous rating scale measurement model of Wright and Masters in a non–randomised outcome study in two different low vision rehabilitation centres in The Netherlands.
Methods:
Visually impaired elderly patients (N=319) from Ophthalmology departments of four hospitals entered our study from July 2000 untill January 2003. Patients were referred either to monodisciplinary (optometrist) rehabilitation (53%) or to a multidisciplinary rehabilitation centre (47%). After a year 73% still participated in our study. All patients administered the questionnaires by self–report, at baseline (T0), three months (T1) and one year (T2) after rehabilitation. Mean person measures (abilities) and effect sizes (ES) at T1 and T2 were calculated for both instruments and for both rehabilitation groups.
Results:
Paired sample t–tests for the VCM1 showed improvement at T1 (p=0.02; ES=0.12 and p=0.003; ES=0.15) for the monodisciplinary and the multidisciplinary groups respectively. At T2 only the multidisciplinary group showed improvement on the VCM1 (p=0.03; ES=0.12). On the LVQOL, no significant improvement or deterioration was found for both groups.
Conclusions:
Although, paired sample t–tests for the two rehabilitation groups showed significant improvement in vision related quality of life over time for the VCM1, the effect sizes appeared to be small. We conclude that the sensitivity to change of both instruments is poor. Whether rehabilitation contributed to vision related quality of life or whether the two vision related quality of life measurement instruments should be used in the future to evaluate rehabilitation outcome remains a matter of further discussion. Improvement of both instruments, but also rehabilitation might be necessary.
Keywords: quality of life • clinical research methodology • low vision