Table 4.

Reliability and validity analysis

Subscale	Number of items	Intraclass correlation coefficients	Cronbach's alpha	Range of item-scale correlations	Convergent validity	Discriminant validity
General Health	1	0.841	NA	NA	NA	NA
General Vision	1	0.889	NA	NA	NA	NA
Ocular pain	2	0.803	0.851	0.893 – 0.903	100	100
Near activities	3	0.901	0.734	0.719 – 0.875	100	100
Distance activities	3	0.908	0.686	0.752 – 0.892	100	100
Vision specific social functioning	2	0.91	0.678	0.887 – 0.889	100	100
Vision specific mental health	4	0.823	0.786	0.596 – 0.837	100	100
Vision specific role difficulties	2	0.888	0.926	0.902 – 0.907	100	100
Vision specific dependency	3	0.826	0.848	0.835 – 0.899	100	100
Driving	3	0.871	0.757	0.575 – 0.953	100	100
Color vision	1	0.717	NA	NA	NA	NA
Peripheral vision	1	0.84	NA	NA	NA	NA

N.A.: Not applicable (needs two or more items).