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Ronald M. Hansen, Anne B. Fulton; Rod-Mediated Increment Threshold Functions in Infants. Invest. Ophthalmol. Vis. Sci. 2000;41(13):4347-4352.
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purpose. To obtain and analyze scotopic increment threshold functions to test
the hypothesis that rod photoreceptor immaturity accounts for the
elevation of infants’ over controls’ dark-adapted thresholds and
elevation of parafoveal over peripheral thresholds in infants.
methods. Using a preferential looking method, thresholds for detection of
2o, 50 msec, blue stimuli presented 10o (parafoveal) or 30o (peripheral) eccentric were measured in
the dark and in the presence of steady red backgrounds. Ten 10-week-old
infants and four control subjects (8–35 years) were tested. To
evaluate pre- and postadaptation site determinants of threshold, a
model of the increment threshold function was fit to the data, and the
dark-adapted threshold (TD) and eigengrau
(AO) were calculated. The values of TD and AO were compared between infants and controls and
between parafoveal and peripheral eccentricities.
results. At both parafoveal and peripheral eccentricities, infants’
values of TD and AO were significantly higher
than those of controls. The locus of the coordinates (AO,
TD) differed significantly between parafoveal and
peripheral eccentricities. In every infant, the parafoveal value of
TD was higher (by 0.3–0.6 log unit) and AO lower (by 0.2–0.5 log unit) than the peripheral value,
whereas controls had no difference in TD and AO at the two eccentricities.
conclusions. The results indicate that both receptoral and postreceptoral
immaturities have a role in the elevation of infants’ over controls’
thresholds. In infants, rod photoreceptor immaturity before the
site of adaptation accounts for elevation of parafoveal over peripheral
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