Table 3.
Internal consistency reliability, concurrent validity, and construct validity at baseline
| |
Internal-consistency reliability |
Concurrent validity |
Construct validity |
||||
|---|---|---|---|---|---|---|---|
| |
|
EQ-5D VAS |
Study eye: ETDRS total letters |
Fellow eye: ETDRS Total letters |
Study eye: ETDRS 73–64 letters |
Study eye: ETDRS 52–35 letters |
|
| VFQ-25 domain | Cronbach’s alpha* | Pearson correlation | Mean ± SD | P value from student’s t-test | |||
| 1. General Health |
N/A |
0.43 |
0.19 |
0.10 |
41.0 ± 24.17 |
33.5 ± 22.07 |
.078 |
| 2. General Vision |
N/A |
0.30 |
0.31 |
0.29 |
60.3 ± 15.27 |
46.4 ± 15.95 |
<.001 |
| 3. Ocular Pain |
0.70 |
0.20 |
0.10 |
0.01 |
78.9 ± 23.67 |
76.1 ± 24.49 |
.52 |
| 4. Near Activities |
0.73 |
0.36 |
0.35 |
0.36 |
65.8 ± 21.93 |
45.1 ± 21.55 |
<.001 |
| 5. Distance Activities |
0.58 |
0.33 |
0.34 |
0.36 |
70.9 ± 23.44 |
51.2 ± 23.99 |
<.001 |
| 6. Social Functioning |
0.64 |
0.33 |
0.31 |
0.34 |
84.8 ± 19.51 |
69.1 ± 27.40 |
<.001 |
| 7. Mental Health |
0.78 |
0.35 |
0.33 |
0.30 |
65.3 ± 24.96 |
44.8 ± 27.62 |
<.001 |
| 8. Role Difficulties |
0.77 |
0.16 |
0.27 |
0.23 |
59.4 ± 30.67 |
44.1 ± 26.40 |
.004 |
| 9. Dependency |
0.85 |
0.37 |
0.34 |
0.34 |
78.0 ± 26.40 |
55.6 ± 33.39 |
<.001 |
| 10. Driving |
0.75 |
0.34 |
0.41 |
0.51 |
65.5 ± 32.09 |
31.8 ± 33.52 |
<.001 |
| 11. Colour Vision |
N/A |
0.19 |
0.18 |
0.14 |
87.7 ± 19.16 |
81.8 ± 24.49 |
.14 |
| 12. Peripheral Vision |
N/A |
0.19 |
0.26 |
0.36 |
75.4 ± 25.83 |
61.4 ± 25.14 |
.003 |
| VFQ-25 Composite | 0.92 | 0.38 | 0.39 | 0.40 | 72.1 ± 17.91 | 56.1 ± 18.00 | <.001 |
* Cronbach’s alpha is only applicable for multi-item scales.