Table 3.

Internal consistency and test-retest reliability of NEI VFQ-25 subscales

	Number of items	Cronbach's alpha	Intraclass correlation, for test-retest reliability	Range of item-scale correlations	Convergent validity*	Discriminant validity**
General health	1	NA***	0.51	NA	NA	NA
General vision	1	NA	0.48	NA	NA	NA
Near vision****	3	0.87 (0.85)	0.76 (0.69)	0.65 – 0.75 (0.69 – 0.73)	100 (100)	93.9 (100)
Distance vision****	3	0.84 (0.79)	0.85 (0.69)	0.67 – 0.75 (0.57 – 0.69)	100 (100)	90.9 (100)
Driving	2	0.58	0.99	0.49 – 0.49	100	50.0
Peripheral vision	1	NA	0.62	NA	NA	NA
Color vision	1	NA	0.74	NA	NA	NA
Ocular pain	2	0.44	0.75	0.28 – 0.28	0	81.8
Vision-specific
Role limitation	2	0.82	0.88	0.70 – 0.70	100	90.9
Dependency	3	0.87	0.90	0.71 – 0.82	100	97.0
Social function	2	0.74	0.88	0.58 – 0.58	100	59.1
Mental health	4	0.84	0.94	0.62 – 0.75	100	90.9
25-item composite	25	0.96	0.94	NA	NA	NA

* The percentage of items that passed the test of convergent validity (as described in the text).

** The percentage of items that passed the test of discriminant validity (as described in the text).

*** NA: Not applicable to single-item scales

**** Scores were recomputed after the substitution of items described in the text. Results of the recomputations are in parentheses.