Table 1.

Stratification for enrollment; target N = 195^a

	Categories for visual processing speed scores (msec)b
Categories for contrast sensitivity scores (log sensitivity)c	<  150	150–350	>  350
≥ 1.5
≥ 1.25 to < 1.5
< 1.25

^a21–22 participants in each cell

^bVisual processing speed measured by UFOV subtest 2

^cContrast sensitivity measured by the Pelli-Robson chart