Table 1.
Conversion Table Using Objective Comparison of Relative Character Sizing between Different Near Charts Tested at 40 cm
| Snellen (20/x) | Snellen (6/×) | Decimal | LogMAR | N-Notation | Rosenbaum | Rosenbaum∗ |
|---|---|---|---|---|---|---|
| 20/20 | 6/6 | 1 | 0 | J1+ | ||
| 20/25 | 6/7.5 | 0.8 | 0.1 | J1+ | J1 | |
| 20/32 | 6/9.5 | 0.63 | 0.2 | J1 | J2 | |
| 20/40 | 6/12 | 0.5 | 0.3 | N5 | J2 | J3 |
| 20/50 | 6/15 | 0.4 | 0.4 | N6 | J3 | J5 |
| 20/63 | 6/19 | 0.32 | 0.5 | N8 | J5 | |
| 20/70 | 6/21 | 0.29 | 0.55† | J7 | ||
| 20/80 | 6/24 | 0.25 | 0.6 | N10 | J7 | |
| 20/100 | 6/30 | 0.2 | 0.7 | N12 | J10 | J10 |
| 20/125 | 6/38 | 0.16 | 0.8 | |||
| 20/160 | 6/48 | 0.12 | 0.9 | N18 | J16 | |
| 20/200 | 6/60 | 0.1 | 1 | N24 | J16 | |
| 20/250 | 6/75 | 0.08 | 1.1 | |||
| 20/320 | 6/96 | 0.063 | 1.2 | N36 | ||
| 20/400 | 6/120 | 0.05 | 1.3 | N48 |
LogMAR = logarithm of the minimum angle of resolution.
∗
Based on the Snellen equivalent conversion provided on the Rosenbaum near chart itself.
†
This row is not in the standard logMAR progression of 0.1 steps but is included as the Rosenbaum chart provided a Snellen equivalent of 20/70 for J7.