A compact device to derive the optical density of human macular pigment (MP
) using heterochromatic flicker photometry is described. The validity of th
e system is assessed by measuring the optical density spectra of MP in 12 h
ealthy subjects and comparing this with well-established previously publish
ed values. The mean spectral absorbance characteristics of MP across subjec
ts corresponds well with accepted values. As reported in other studies, our
measurements show a wide Variation of MP optical densities between individ
uals. In our technique within-subject variability is low; standard deviatio
ns are between 0.025 and 0.15 in most cases. The overall optical density of
MP ranged from 0.08 to 0.84 with a mean of 0.496 and standard deviation of
0.257 at 460 nm. The stimulus size was 0.95 degrees. The unique feature of
the technique is that it allows free viewing (not Maxwellian View) of the
stimulus, it can be conducted easily and quickly and does not need frequent
re-calibration. (C) 2000 The College of Optometrists. Published by Elsevie
r Science Ltd. All rights reserved.