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Development of the Cone ERG in Infants

From the Department of Ophthalmology, Children’s Hospital and Harvard Medical School, Boston, Massachusetts.

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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				A. Moskowitz, R. M. Hansen, J. D. Akula, S. E. Eklund, and A. B. Fulton Rod and Rod-Driven Function in Achromatopsia and Blue Cone Monochromatism Invest. Ophthalmol. Vis. Sci., February 1, 2009; 50(2): 950 - 958. [Abstract] [Full Text] [PDF]

				R. M. Hansen, A. Moskowitz, and A. B. Fulton Multifocal ERG Responses in Infants Invest. Ophthalmol. Vis. Sci., January 1, 2009; 50(1): 470 - 475. [Abstract] [Full Text] [PDF]

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