Table IV.

Additional psychophysical measures: Macular Pigment Optical Density

Variable	Statistic	Early	Intermediate	Normal	P-value Overall	P-value Early vs Intermediate	P-value Early vs Normal	P-value Intermediate vs Normal
Avg OD on radius 0.25	N	33	47	21	0.61	0.35	0.86	0.54
	Mean (SD)	0.64 (0.22)	0.68 (0.27)	0.63 (0.19)
	Min, Median, Max	0.3, 0.6, 1.2	0.2, 0.7, 1.2	0.3, 0.6, 1.0
Avg OD on radius 0.5	N	33	47	21	0.52	0.35	0.95	0.34
	Mean (SD)	0.54 (0.18)	0.60 (0.24)	0.54 (0.18)
	Min, Median, Max	0.2, 0.5, 0.9	0.1, 0.6, 1.1	0.2, 0.5, 0.9
Avg OD on radius 1	N	33	47	21	0.56	0.51	0.59	0.33
	Mean (SD)	0.44 (0.16)	0.45 (0.19)	0.42 (0.17)
	Min, Median, Max	0.2, 0.4, 0.7	0.0, 0.5, 0.8	0.1, 0.4, 0.8
Avg OD on radius 1.75	N	33	47	21	0.63	0.86	0.44	0.37
	Mean (SD)	0.23 (0.10)	0.23 (0.11)	0.20 (0.09)
	Min, Median, Max	0.1, 0.2, 0.4	0.0, 0.2, 0.4	0.1, 0.2, 0.5

Overall p-value based on Kruskal-Wallis test of difference among medians.

Pair-wise p-values based on Wilcoxon rank sum test of difference between medians.