Background
Methods
Design and participants
Measurements
Patient characteristics
Vision-related quality-of-life
Validation and statistical analyses
Assessing dimensionality and local independence
IRT calibration
Results
Patient characteristics
Gender | ||
Female | 183 | 61.8% |
Male | 113 | 38.2% |
Age
| ||
< 75 years | 76 | 25.7% |
≥75 years | 220 | 74.3% |
LogMAR visual acuity*
| ||
< 0.52 mild vision loss | 97 | 32.9% |
≥ 0.52 low vision/blindness | 198 | 67.1% |
Main cause of vision loss in best eye*
| ||
Age-related macular degeneration | 154 | 52.6% |
Other eye conditions | 139 | 47.4% |
Rehabilitation type
| ||
Optometric service | 161 | 54.4% |
Multidisciplinary service | 135 | 45.6% |
Administration type*
| ||
Self-report | 108 | 37.1% |
Assisted | 183 | 62.9% |
Item non-response and goodness-of-fit
Differential item functioning
Item content | Subgroups | α |
β
1
|
β
2
|
β
3
|
β
4
|
β
5
| G2
| df | p | ESΔmax
|
θ
| |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic aspects
| |||||||||||||
7. | Eyes getting tired | Low vision | 2.50 | -0.93 | -0.65 | -0.10 | 0.32 | 2.13 | 15.7 | 5 | 0.008 | -0.80 | -0.80 |
Moderate vision loss | 2.50 | -1.37 | -1.23 | -0.54 | 0.10 | 1.86 | |||||||
Mobility
| |||||||||||||
3. | Seeing steps or curbs* | Low vision | 2.38 | -0.97 | -0.61 | -0.01 | 0.21 | 1.56 | 14.2 | 1 | < 0.001 | -0.74 | 0.20 |
Moderate vision loss | 5.76 | -0.96 | -0.71 | -0.26 | -0.02 | 1.68 | |||||||
Adjustment
| |||||||||||||
1. | Vision in general | Self | 1.99 | -1.98 | -1.44 | -0.14 | 0.38 | 2.33 | 19.4 | 5 | 0.002 | -0.70 | -2.00 |
Assisted | 1.99 | -2.47 | -2.30 | -0.56 | -0.09 | 2.33 | |||||||
1. | Vision in general | Male | 2.08 | -2.05 | -1.44 | 0.04 | 0.40 | 1.95 | 17.9 | 5 | 0.003 | 0.62 | 2.60 |
Female | 2.08 | -1.83 | -1.57 | -0.27 | 0.24 | 3.37 | |||||||
12. | Unhappy situation in life†
| Male | 3.27 | -0.74 | -0.31 | 0.56 | 1.03 | 3.06 | 15.4 | 5 | 0.009 | 1.00 | 5.40 |
Female | 3.27 | -0.39 | -0.27 | 0.51 | 0.88 | 7.57 | |||||||
Reading and fine work
| |||||||||||||
19. | Reading labels | AMD | 3.77 | -1.34 | -1.21 | -0.94 | -0.46 | 0.68 | 17.8 | 5 | 0.003 | 0.24 | -0.80 |
Other | 3.77 | -1.48 | -1.16 | -0.63 | -0.51 | 0.68 | |||||||
24. | Using tools | Male | 1.83 | -1.22 | -0.92 | -0.38 | -0.15 | 1.13 | 35.2 | 5 | < 0.001 | -1.22 | -1.00 |
Female | 1.83 | -1.80 | -1.58 | -1.39 | -0.94 | 1.05 |
Re-calibration after removing items
Item content per dimension | α |
β
1
|
β
2
|
β
3
|
β
4
|
β
5
| X2
| df | p | |
---|---|---|---|---|---|---|---|---|---|---|
Basic aspects
| ||||||||||
6. | Seeing moving objects | 2.06 | -1.21 | -0.66 | 0.13 | 0.66 | 2.55 | 19.6 | 20 | 0.49 |
7. | Eyes getting tired | 2.61 | -1.25 | -0.96 | -0.29 | 0.25 | 2.10 | 17.0 | 17 | 0.45 |
8. | Seeing the television | 2.18 | -1.69 | -1.18 | -0.34 | 0.21 | 1.98 | 17.1 | 18 | 0.52 |
9. | Glare (dazzled by lights) | 1.81 | -2.17 | -1.80 | -1.20 | -0.51 | 1.76 | 24.8 | 19 | 0.17 |
10. | Getting right amount light | 2.12 | -1.83 | -1.26 | -0.37 | 0.22 | 2.32 | 13.0 | 20 | 0.88 |
Mobility
| ||||||||||
2. | Night vision inside house | 1.66 | -1.42 | -0.88 | 0.32 | 0.85 | 3.16 | 24.6 | 22 | 0.31 |
3. | Seeing steps or curbs | 3.56 | -1.04 | -0.68 | -0.09 | 0.17 | 1.55 | 13.9 | 20 | 0.84 |
4. | Depth/distance perception | 2.41 | -0.80 | -0.45 | 0.09 | 0.51 | 1.98 | 23.3 | 25 | 0.56 |
15. | Getting around outdoors | 5.26 | -1.07 | -0.75 | -0.14 | 0.22 | 1.72 | 7.3 | 18 | 0.99 |
16. | Crossing a road with traffic | 3.35 | -1.11 | -0.69 | -0.25 | 0.12 | 1.52 | 17.7 | 22 | 0.73 |
Adjustment
| ||||||||||
11. | Understand eye condition | 1.26 | -0.94 | -0.47 | 0.22 | 0.68 | 3.48 | 17.0 | 21 | 0.71 |
12. | Unhappy situation in life | 3.23 | -0.63 | -0.37 | 0.51 | 0.93 | 3.22 | 10.5 | 21 | 0.97 |
13. | Frustration with doing tasks | 3.41 | -1.06 | -0.69 | 0.02 | 0.38 | 2.44 | 19.3 | 19 | 0.44 |
14. | Visiting friends and family | 1.37 | -0.44 | -0.13 | 0.52 | 0.89 | 2.99 | 16.5 | 21 | 0.74 |
Reading and fine work
| ||||||||||
17. | Reading large print | 2.14 | -0.14 | 0.19 | 0.85 | 1.17 | 2.10 | 23.2 | 27 | 0.68 |
18. | Reading newspaper/books | 3.98 | -1.42 | -1.06 | -0.61 | -0.26 | 0.92 | 23.7 | 25 | 0.54 |
19. | Reading labels | 3.50 | -1.79 | -1.44 | -0.94 | -0.54 | 0.79 | 13.2 | 22 | 0.93 |
20. | Reading letters and mail | 5.02 | -1.28 | -0.93 | -0.36 | 0.02 | 0.98 | 21.9 | 22 | 0.47 |
21. | Finding out the time | 1.91 | -0.50 | -0.16 | 0.59 | 1.13 | 2.27 | 25.8 | 29 | 0.64 |
22. | Writing | 3.55 | -1.04 | -0.71 | -0.17 | 0.17 | 1.06 | 21.2 | 27 | 0.78 |
23. | Reading own handwriting | 3.17 | -0.81 | -0.41 | 0.11 | 0.51 | 1.31 | 24.5 | 26 | 0.55 |