Table 3.
Intraobserver Error for Each Vascular Parameter Quantification in Subset of Five Eyesa
| Subject 1 | Subject 2 | Subject 3 | |||||
|---|---|---|---|---|---|---|---|
| Characteristic | Right Eye | Left Eye | Right Eye | Left Eye | Left Eye | ||
| Vessel area density | Temporal small quadrant | Scan 1 | 0.49 | 0.38 | Excludedb | 0.36 | 0.34 |
| Scan 2 | 0.49 | 0.46 | Excludedb | 0.38 | 0.43 | ||
| CoV | 0.001 | 0.098 | NA | 0.022 | 0.112 | ||
| Nasal small quadrant | Scan 1 | 0.46 | 0.34 | Excludedb | 0.39 | 0.40 | |
| Scan 2 | 0.41 | 0.38 | Excludedb | 0.44 | 0.45 | ||
| CoV | 0.063 | 0.044 | NA | 0.060 | 0.055 | ||
| Temporal large quadrant | Scan 1 | 0.72 | 0.46 | Excludedb | 0.49 | Excludedb | |
| Scan 2 | 0.83 | 0.45 | Excludedb | 0.49 | Excludedb | ||
| CoV | 0.073 | 0.011 | NA | 0.002 | NA | ||
| Nasal large quadrant | Scan 1 | 0.45 | Excludedb | Excludedb | 0.42 | 0.49 | |
| Scan 2 | 0.47 | Excludedb | Excludedb | 0.41 | 0.55 | ||
| CoV | 0.019 | NA | NA | 0.008 | 0.060 | ||
| Nonperfusion area (mm2) | Temporal small quadrant | Scan 1 | 1.19 | 1.54 | Excludedb | 1.45 | 1.57 |
| Scan 2 | 1.30 | 1.35 | Excludedb | 1.48 | 1.31 | ||
| CoV | 0.046 | 0.068 | NA | 0.010 | 0.090 | ||
| Nasal small quadrant | Scan 1 | 1.44 | 1.55 | Excludedb | 1.38 | 1.36 | |
| Scan 2 | 1.47 | 1.42 | Excludedb | 1.24 | 1.22 | ||
| CoV | 0.013 | 0.043 | NA | 0.056 | 0.056 | ||
| Temporal large quadrant | Scan 1 | 3.95 | 5.38 | Excludedb | 5.37 | Excludedb | |
| Scan 2 | 3.10 | 5.36 | Excludedb | 5.73 | Excludedb | ||
| CoV | 0.120 | 0.002 | NA | 0.032 | NA | ||
| Nasal large quadrant | Scan 1 | 5.78 | Excludedb | Excludedb | 5.38 | 5.02 | |
| Scan 2 | 5.84 | Excludedb | Excludedb | 5.39 | 4.94 | ||
| CoV | 0.006 | NA | NA | 0.000 | 0.009 | ||
| Mean large-vessel diameterc (µm) | Scan 1 | 54.45 | 70.64 | 53.14 | 58.63 | 57.03 | |
| Scan 2 | 58.81 | 67.44 | 53.01 | 58.98 | 59.22 | ||
| CoV | 0.039 | 0.024 | 0.001 | 0.003 | 0.019 | ||
| Mean large-vessel tortuosityd | Scan 1 | 1.09 | 1.10 | 1.14 | 1.16 | 1.12 | |
| Scan 2 | 1.13 | 1.10 | 1.15 | 1.13 | 1.11 | ||
| CoV | 0.018 | 0.003 | 0.003 | 0.013 | 0.002 | ||
a
Subject 1 is full term; subjects 2 and 3 are preterm. CoV, coefficient of variation (low CoV represents high observer repeatability); NA, CoV value cannot be calculated due to lack of data after exclusion criteria were applied.
b
More than 30% of quadrant area missing blood vessel information, or the signal-to-noise ratio of that quadrant was less than 80% of average signal-to-noise ratio for entire image.
c
Calculated from large vessels as previously described.53
d
Ratio of the length of the curve of a large-vessel segment over the distance between two ends of the curve.54