Table 3.
Visual acuity by each testing method and by clinical visual acuity subgroups
| Visual Acuity | Clinical VA |
||
|---|---|---|---|
| Overall | 20/40 or better | 20/50 or worse | |
|
| |||
| No. of eyes | |||
| N | 1016 | 640 | 376 |
| Clinical VA, letter score (converted from Snellen fraction) a | |||
| Mean (SD) | 68.6 (17.1) | 78.7 (5.8) | 51.3 (16.1) |
| Median (IQR) | 75 (60, 80) | 80 (75, 85) | 58 (45, 65) |
| Protocol VA, letter score (eETDRS) | |||
| Mean (SD) | 76.3 (15.6) | 84.5 (7.0) | 62.3 (16.3) |
| Median (IQR) | 82 (67, 87) | 86 (82, 89) | 64 (55, 71) |
| VA difference (protocol - clinical), letter score b | |||
| Mean (SD) | 7.6 (9.6) | 5.8 (6.6) | 10.7 (12.6) |
| Median (IQR) | 7 (2, 13) | 5 (2, 10) | 10 (2, 20) |
| VA difference (protocol - clinical), N (%) | |||
| Protocol ≥15 letters better | 204 (20%) | 60 (9%) | 144 (38%) |
| Protocol 10–14 letters better | 169 (17%) | 121 (19%) | 48 (13%) |
| Protocol 5–9 letters better | 256 (25%) | 197 (31%) | 59 (16%) |
| Same ± 4 letters | 316 (31%) | 229 (36%) | 87 (23%) |
| Protocol 5–9 letters worse | 40 (4%) | 19 (3%) | 21 (6%) |
| Protocol 10–14 letters worse | 17 (2%) | 11 (2%) | 6 (2%) |
| Protocol ≥15 letters worse | 14 (1%) | 3 (<1%) | 11 (3%) |
a
Converted letter score = 85 + 50 × log10(Snellen fraction), rounded to the nearest letter, or = 0 for Snellen fractions <20/800.
b
VA difference outliers were truncated at the raw overall mean ± 3 SD (7.7 ± 3 × 10.3).