The effect of age on human cone and rod ganzfeld electroretinograms.

The ganzfeld-evoked electroretinogram (ERG) is the most effective measure of the mass electrical response of cones and rods; however, all variables affecting the various components of the ERG have not been identified. The scotopic b-wave amplitude has been appreciated to be age-dependent, but little or no information exists in the literature regarding age dependency for other components. Linear regression analysis against age and multiple regression analysis against age and log intensity of the stimulus were performed on ERG responses from 24 prospectively normal subjects. Significant age dependency was found for scotopic rod-mediated b-wave amplitude, scotopic mixed rod-and cone-mediated bx-wave amplitude, and for photopic cone-mediated and b-wave amplitude. No significant age correlation was found for dark-adapted cone a-wave amplitude, scotopic cone-mediated x-wave amplitude, scotopic a-wave amplitude from mixed rod and cone responses to bright stimuli, or for implicit times for any scotopic or photopic responses. These findings indicate that for clinical patient evaluation, age-corrected normal ranges derived from linear or multiple regression coefficients should be used for rod- and cone-mediated b-wave response, whereas normal ranges derived from mean and standard deviation are more appropriate for scotopic a-wave amplitude, scotopic cone-mediated x-wave amplitude, and for all implicit times.