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J. Wang, G.M. Tondel, T.R. Candy; Infants’ Accommodative Stability during Preferential-looking Acuity Measurements . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1994.
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Purpose: Accommodation has not been measured previously during preferential-looking acuity evaluation in infants. This study assessed accommodative stability as a function of target spatial frequency. The goal was to assess the contribution of image defocus to estimates of the infants’ acuity. Methods: The camera of an eccentric Photorefractor (PowerRefractor) was placed immediately adjacent to the grating on a preferential-looking Teller card. Binocular accommodative responses of infants aged 7-24 wks were recorded for 5 seconds, at 25Hz, while the infant viewed the grating on the card. The procedure was repeated with each infant for a number of target spatial frequencies. Results: The Teller Card acuity estimates were all within the normal range for the infants’ ages. The mean accommodative response and its standard deviation were calculated for each trial. The mean response varied across infants including both under- and over-accommodation relative to the demand. This accommodative error decreased with increasing spatial frequency, below the acuity threshold. The standard deviation of the responses in the individual trials also decreased with increasing spatial frequency. These effects can be predicted by considering depth of focus as a function of spatial frequency. Conclusions: Infants’ accommodative performance improves as a function of spatial frequency during preferential-looking acuity measurements with the Teller Cards. The relative contribution of age and predicted depth of focus will be discussed.
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