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Angela M Brown, Delwin T Lindsey, Joanna G Cammenga, Lynnell Chandler, Sarah Heintzman, Holly Bookless, Peter J Giannone; The contrast sensitivity of the newborn infant. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2736.
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© ARVO (1962-2015); The Authors (2016-present)
By law, every newborn infant in the state of Ohio must have his/her hearing tested. **Why not vision?** The goal of this project was to take the first steps towards developing a quick, easy-to-use screening test for visual function in newborn infants.
We measured the log10 contrast sensitivity (logCS) of 89 healthy newborn infants (age ≤ 3 days) using a fixation-and-following method (Brown & Yamamoto, 1986) similar to the Teller Acuity Cards. Each H30 x W55 cm gray card had a 20/4000 or 20/6400 square-wave grating of 25%-100% contrast centered within the card, with a peephole in the center. These gratings were, respectively, 2.15 and 2.83 octaves below 20/900, the visual acuity of the normal newborn infant (Brown & Yamamoto), and the contrasts were in 0.15 log unit steps. After attracting the infant’s attention to fixate the grating, the adult tester displaced the card laterally to elicit following eye movements. LogCS was the logarithm of the reciprocal of the lowest contrast value the infant followed. The main tester (AMB) had 30 prior years’ experience testing infants, and was blind to the identity of the cards, but not the order of their contrast values. Another tester provided limited data. Of the 53 infants tested by AMB with 20/4000 vertical gratings, 31 were also tested with a 20/4000 horizontal grating (12 with sharp and 19 with vignetted vertical edges). AMB tested 28 infants with the 20/6400 grating.
All awake infants were successfully tested and saw at least one grating. We discarded the first 10 infants’ data in each condition due to tester practice. Infant logCS was 0.30 ±0.13 SD for 20/4000 vertical gratings. LogCS for horizontal gratings was significantly lower (0.23 ±0.12, paired t(20)=4.713, p<0.001), suggesting a more sensitive, possibly subcortical pathway for the vertical gratings. LogCS at 20/6400 was 0.22 ±0.15.
The logCS of the normal newborn infant is 0.30, which is about 2 log units (a factor of 100) worse than the logCS of the normal adult. This value was measured using 20/4000 vertical gratings, which produced the best logCS among the conditions we examined. Because every normal neonate was testable, this card procedure shows promise for screening for visual disorders in newborn infants.
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