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Ronald M. Hansen, Anne B. Fulton; Development of the Cone ERG in Infants. Invest. Ophthalmol. Vis. Sci. 2005;46(9):3458-3462. doi: 10.1167/iovs.05-0382.
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purpose. To assess cone photoreceptor and cone-mediated postreceptoral retinal function in infants.
methods. ERG responses to a 1.8-log unit range of long-wavelength flashes on a white, rod-saturating background were recorded in 4-week-old (n = 22) and 10-week-old (n = 28) infants and control adults and children, 8 to 40 years of age (n = 13). A model of the activation of cone phototransduction was fit to the a-waves. Sensitivity (S CONE ) and saturated-response amplitude (R CONE ) were calculated. The amplitude and implicit time of the b-wave were examined as a function of stimulus intensity. The cone photoresponse parameters were compared to the rod photoresponse parameters (S ROD and R ROD ) in the same subjects.
results. S CONE and R CONE in infants were significantly smaller than in the mature control subjects. The mean S CONE was 64% and 68%, and the mean R CONE was 63% and 72% in 4- and 10-week-olds, respectively. The mean rod photoresponse parameters were considerably less mature, as the mean S ROD was 35% and 46%, and the mean R ROD was 39% and 43% of mature values at 4 and 10 weeks. The b-wave stimulus–response functions in the 4- and 10-week-old infants did not show the photopic hill that was characteristic of the children’s and adults’ photopic b-waves.
conclusions. Peripheral cone function is relatively more mature than rod function in young infants. The lack of a photopic hill is hypothesized to result from immaturity in the relative contributions of ON and OFF bipolar cell responses.
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