Results: The proportion of ungradable photographs when using 45o three-field nonmydriatic, 45o single-field mydriatic, and 30o seven-field mydriatic were, respectively: 6.41% (95% CI: 3.86 - 8.95); 2.51% (95% CI: 0.88 - 4.13); 2.23% (95% CI: 0.69 - 3.76).