Table 7.
Final multivariable model estimates for VA difference (protocol – clinical)
| Final Multivariable Model Effectsa | Estimate | (95% CI) | P-value |
|---|---|---|---|
|
| |||
| Clinical VA, 1-line (5 letters converted from Snellen fraction) b | −1.3 | (−1.5, −1.1) | <0.001 |
| Hemoglobin A1c, % | −0.3 | (−0.6, −0.0) | 0.05 |
| Eye enrollment | <0.001 | ||
| Fellow Eye | 1.9 | (1.0, 2.8) | <0.001 |
| Study Eye (reference) | 0.0 | ||
| Clinical VA correction method | 0.06 | ||
| Refracted | −3.0 | (−5.9, −0.1) | 0.04 |
| Glasses or contacts | −1.8 | (−3.3, −0.3) | 0.02 |
| Pinhole only | −1.5 | (−3.5, 0.5) | 0.14 |
| Uncorrected (reference) | 0.0 | ||
a
The final multivariable model for VA difference (protocol - clinical) included N = 901 eyes with no missing covariate values in a linear mixed model with nested random effects on the intercept for correlation within sites and participants; VA difference outliers were truncated at the raw overall mean ± 3 SD (7.7 ± 3 × 10.3).
b
Converted letter score = 85 + 50 × log10(Snellen fraction), rounded to the nearest letter, or = 0 for Snellen fractions <20/800.
The intraclass correlation was 0.14 within sites and 0.38 within participants within sites. The conditional R2 (variance explained by fixed and random factors) was 0.52.