A portable instrument for measuring macular pigment with central fixation.

PURPOSE To evaluate the reliability and validity of a portable instrument for measuring macular pigment optical density. METHODS The instrument is small, uses light emitting diodes as light sources and the principles of heterochromatic flicker photometry of comparing foveal and extra-foveal minimum flicker matches. It uses central fixation for the extra-foveal matches, which subjects found easier than eccentric fixation. Subjects with healthy eyes used the instrument to measure their pigment density in a number of eye clinics. RESULTS The mean pigment density in 124 eyes in 124 individuals was 0.41 +/- 0.16 (mean +/- SD), there was no significant change with age but the density was less in females, those with light irides, smokers, subjects on diets low in precursor carotenoids and in those exposed to several hours of daylight every day or who used sun beds. CONCLUSIONS The portable instrument gave valid and reliable data that confirmed published values for macular pigment. It was convenient to use in the clinic and has potential as a screening tool.