Table 2.

Distributional characteristics, internal consistency reliability, and construct validity of VFQ-25 scales at baseline

Scale	N	Mean	SD	Range	Number of items	Cronbach's alpha†	Spearman correlations with ETDRS
General vision	670	69.5	17.4	20.0 – 100.0			0.39***
Ocular pain	671	89.1	15.2	12.5 – 100.0	2	0.68	0.02
Near vision	671	75.8	21.7	8.3 – 100.0	3	0.81	0.38***
Distance vision	671	82.9	17.9	16.7 – 100.0	3	0.72	0.35***
Social function	671	93.9	12.9	12.5 – 100.0	2	0.64	0.25***
Mental health	671	77.2	21.3	0.0 – 100.0	4	0.79	0.28***
Role limitations	670	81.4	23.1	0.0 – 100.0	2	0.75	0.32***
Dependency	670	91.3	17.4	0.0 – 100.0	3	0.83	0.29***
Driving	632	81.1	20.7	0.0 – 100.0	3	0.73	0.34***
Color vision	665	94.6	14.7	0.0 – 100.0			0.12**
Peripheral vision	669	88.4	19.4	25.0 – 100.0			0.25***
Overall VFQ-25 score	671	84.1	13.5	16.2 – 100.0	25	0.93	0.40***

^†Computed only for multi-item scales

*p < 0.05; **p < 0.01; ***p < 0.001

ETDRS = Early Treatment Diabetic Retinopathy Study Visual Acuity Rating; SD = standard deviation; VFQ-25 = 25-Item Visual Function Questionnaire