Activity Limitation in Glaucoma: Objective Assessment by the Cambridge Glaucoma Visual Function Test.

PURPOSE

We design and evaluate a computer-based objective simulation of activity limitation related to glaucoma.

METHODS

A cross-sectional study was performed involving 70 glaucoma patients and 14 controls. Mean age was 69.0 ± 10.2 years; 49 (58.3%) were male. The Cambridge Glaucoma Visual Function Test (CGVFT) was administered to all participants. Rasch analysis and criterion, convergent, and divergent validity tests assessed the psychometric properties of the CGVFT. Regression modeling was used to determine factors predictive of CGVFT person measures. Sociodemographic information, better and worse eye visual field parameters, visual acuity, contrast sensitivity, and the Rasch-analyzed Glaucoma Activity Limitation-9 (GAL-9) and Visual Function Questionnaire Utility Index (VFQUI) questionnaire responses were recorded.

RESULTS

From 139 pilot CGVFT items, 59 had acceptable fit to the Rasch model, with acceptable precision (person separation index, 2.13) and targeting. Cambridge Glaucoma Visual Function Test person measure (logit) scores increased between controls (-0.20 ± 0.08) and patients with mild (-0.15 ± 0.08), moderate (-0.13 ± 0.10), and severe (-0.05 ± 0.10) glaucoma (P < 0.001, ANOVA) indicating good criterion validity. Correlation coefficients of 0.455 (P < 0.001) between CGVFT and GAL-9 person measures and 0.399 (P = 0.005) between CGVFT and VFQUI person measures demonstrated convergent validity. Divergent validity was suboptimal. On multivariable analysis, lower better eye mean deviation and greater age were associated with worsening CGVFT person measures (P ≤ 0.001).

CONCLUSIONS

The CGVFT is a computerized visual challenge test administered to a cohort of glaucoma patients. It may benefit glaucoma patients, careers, health care providers, and policy makers, providing increased awareness of activity limitation due to glaucoma.