Optical and photoreceptor immaturities limit the spatial and chromatic vision of human neonates.

We examine the contributions of preneural mechanisms, i.e., the optics of the eye and the aperture, spacing, and efficiency of foveal cones, to poor spatial and chromatic vision in human neonates. We do so by comparing the performances of ideal observers incorporating the characteristics of the optics and the foveal cones of adults and neonates. Our analyses show that many, but not all, of the differences between neonatal and adult contrast sensitivities and grating acuities can be explained by age-related changes in these factors. The analyses also predict differing growth curves for vernier and grating acuities. Finally, we demonstrate that preneural mechanisms constrain chromatic discrimination in human neonates and that discrimination failures may reflect poor visual efficiency rather than immature chromatic mechanisms per se.