Summary of the performance of each test chart in predicting the ability to read a number-plate at 20 m
| Chart | ‘Overlap zone’ | Number in overlap zone | False positive rate (%) | False negative rate (%) | Sensitivity (%) | Specificity (%) | |
|---|---|---|---|---|---|---|---|
| Min | Max | ||||||
| Snellen (full line correct) | 6/9 | 6/36 | 59 | 15 | 2 | 97 | 63 |
| ETDRS style (logMAR) | +0.12 | +0.84 | 50 | 14 | 6 | 91 | 61 |
| Landolt (logMAR) | +0.30 | +0.98 | 51 | 35 | 2 | 97 | 18 |
Parameters are defined in table 1.