Abstract
Purpose: :
Development of the visual system is influenced by retinal image quality. The infant eye is smaller than that of the adult and its total optical power is greater. While infants' refractive errors and monochromatic aberrations have been measured centrally, little is known about the peripheral optics and their effects on retinal image quality.
Methods: :
Infants from 2–4 months of age, and adults, were presented with a high contrast cartoon image moving sequentially between horizontal eccentricities of 0, 4, 8, 12 & 16 degrees from the camera of an eccentric photorefractor recording at 25Hz (Multichannel systems). The photorefractor estimates the defocus of the eye along the vertical meridian. The data were averaged over 2 seconds at each eccentricity and normalized to the defocus estimate at 0 deg eccentricity, to determine how the defocus changed relative to central fixation.
Results: :
The adult data were consistent with the previous literature (Seidemann, Schaeffel, Guirao, Lopez–Gil & Artal (2002)) in that the measured defocus increased with eccentricity along the horizontal meridian. The relative defocus estimate reached 1 D at approximately 15 degrees eccentricity. The infant data showed little immaturity, also only approaching a 1D relative defocus at this eccentricity.
Conclusions: :
Although the photorefractor summarizes all the components of peripheral optical quality into a defocus estimate, the defocus estimates recorded here are notably stable with eccentricity. This suggests that there are no dramatic immaturities in any of the higher order aberrations across the mid–peripheral optics of the young infant eye.
Keywords: infant vision • optical properties • visual development: infancy and childhood