Macular pigment and the edge hypothesis of flicker photometry.
Heterochromatic flicker photometry is commonly used to measure macular pigment optical density (MPOD) in the human retina. It has been proposed, and accepted by many, that the MPOD so measured represents the value at a retinal location corresponding to the edge of the flickering, circular stimulus. We have investigated this proposal by using a series of annular stimuli to determine the MPOD distribution in the central 1.5 degrees of the retina for both eyes of 10 subjects. The MPOD obtained using a 1.5 degrees circular stimulus matched the MPOD distribution at a retinal eccentricity that was always less than the stimulus radius, and averaged, for the 10 subjects, 51% of the stimulus radius. Similar results were obtained using a 1 degrees stimulus. Thus the edge hypothesis is inconsistent with our data. We suggest that involuntary eye movements may be responsible for an apparent edge effect.
Bone
Richard A
RA
Department of Physics, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA. bone@fiu.edu
Landrum
John T
JT
Gibert
Jorge C
JC
D005133:Eye Movements; D006801:Humans; D008266:Macula Lutea / Q000737:chemistry*; D008960:Models, Psychological; D010775:Photic Stimulation / Q000379:methods; D010783:Photometry / Q000379:methods; D011601:Psychophysics; D012168:Retinal Pigments / Q000032:analysis*
D012168:Retinal Pigments