In patients with a plasma lutein concentration below the mean level in 20 age-matched healthy subjects ( mean 105.3 ng/mL ; n = 13 in lutein group , n = 15 in control group ) , the control MPOD values significantly ( P = 0.0430 ) decreased at 4 months ( mean baseline , 0.437 DU ; 4 months , 0.404 DU ) .