[Aging and the focal macular electroretinogram]

Focal macular electroretinograms (MERGs) were recorded with a fundus monitor through an infrared television fundus camera in 112 eyes of 112 normal subjects (68 males, 44 females), using three stimulus spots 5 degrees, 10 degrees, and 15 degrees in diameter. The amplitude and the implicit time of the a-wave, h-wave, and oscillatory potentials (OPs), and the ratio of amplitude of the b-wave to the a-wave (b/a ratio) at each stimulus spot were compared in terms of aging and sex. The amplitude of all components decreased significantly (p < 0.01-0.05) after the fifth decade, and there was a tendency for OPs to decrease more than the a-wave and b-wave. There was no significant effect of age on the h/a ratio and the implicit time of each component. The ratio of increase of amplitude to the enlargement of stimulus spot showed no significant changes with age. There was no significant difference in each component in terms of amplitude and implicit time with sex. The decrease of amplitude of all components after the fifth decade suggests aging of the macular cones. The tendency toward decreasing OPs also suggests aging of the inner retina in the macular region. The proportional changes of amplitude recorded with three different sizes of stimulus spots indicate that there is no significant effect of aging on the fovea, parafovea, or perifovea.