Time trade-off utilities and 95% CIs as a function of distance visual acuity: a comparison of findings from Brown et al10 with the present study
| VA group | Data from Brown et al10 | Data from present study | |||
|---|---|---|---|---|---|
| Snellen fraction | LogMAR equivalent | Mean 95% CI | logMAR | Mean 95% CI | |
| CF, counting fingers; logMAR, logarithm of the minimum angle of resolution; LP, light perception; VA, visual acuity. | |||||
| Data from Brown et al10 are for distance VA in the better eye, whereas those from the present study are for distance binocular VA. Since our utility estimates are based on binocular viewing, we prefer to relate these to binocular measures of visual function, although practically there is little difference between the two measures. Others have shown that binocular VA and VA in the better eye are comparable predictors of visual disability.27 The VA groups quoted in Brown et al10 are in Snellen, which have been converted here to their logMAR equivalence for ease of comparison, and the nearest equivalent categories have been used for data from the present study. | |||||
| 1 | 20/20 to 20/25 | 0–0.10 | 0.89 (0.82 to 0.96) | ⩽0.1 | 0.93 (0.86 to 0.99) |
| 2 | 20/30 to 20/50 | 0.18–0.40 | 0.81 (0.73 to 0.89) | 0.12–0.40 | 0.86 (0.78 to 0.93) |
| 3 | 20/60 to 20/100 | 0.49–0.70 | 0.57 (0.47 to 0.67) | 0.42–0.70 | 0.74 (0.64 to 0.83) |
| 4 | 20/200 to 20/400 | 1.00–1.30 | 0.52 (0.38 to 0.66) | 0.72–1.30 | 0.68 (0.57 to 0.79) |
| 5 | CF to LP | >1.30 | 0.40 (0.29 to 0.50) | >1.30 | 0.76 (0.37 to 1.15) |