Categorising vision: logMAR and Snellen measurement scales, the WHO and UK categories of visual impairment (VI)
| Acuity measurement scales | Vision categories (using best achievable acuity with both eyes open) | |||
|---|---|---|---|---|
| LogMAR(linear scale) | Snellen(geometric scale) | WHO definition of visual impairment | UK criteria for visual impairment certification | |
| Full field of vision | Very reduced field of vision | |||
| –0.1 | 6/4.8 | No sight impairment | No sight impairment* | No sight impairment |
| 0.0 | 6/6 | |||
| 0.1 | 6/7.5 | |||
| 0.2 | 6/9 | |||
| 0.3 | 6/12 | |||
| 0.4 | 6/15 | |||
| 0.5 | 6/18 | Sight impairment (previously termed partially sighted) | ||
| 0.6 | 6/24 | Moderate visual impairment | ||
| 0.7 | 6/30 | |||
| 0.8 | 6/36 | |||
| 0.9 | 6/48 | |||
| 1.0 | 6/60 | Sight impairment | Severe sight impairment | |
| 1.1 | 5/60 | Severe visual impairment | ||
| 1.2 | 4/60 | |||
| 1.3 | 3/60 | |||
| 1.4 | 2/60 | Blindness | Severe sight impairment | |