Development of contrast sensitivity in the human infant.
Contrast sensitivity and grating acuity were measured using the sweep VEP method in a group of 48 infants from 2 to 40 weeks of age and in a group of 10 adults. Sinusoidal gratings were reversed in contrast at 12 alternations per sec at a space-average luminance of 220 cd/m2. During 10 sec trials, either the contrast or the spatial frequency was increased in a series of 19 steps. Thresholds were estimated by extrapolation of the VEP response functions to zero amplitude. The contrast threshold at low spatial frequencies developed rapidly from 7% contrast at 2-3 weeks to an asymptote of 0.5% at 9 weeks. For adults, maximum sensitivity at low spatial frequencies was 0.32-0.22%. The sweep VEP estimate of grating acuity showed a gradual increase in spatial frequency with age, starting at 5 c/deg during the first month and reaching 16.3 c/deg at 8 months. The mean adult acuity was 31.9 c/deg. There appeared to be two phases in the development of contrast sensitivity and acuity. Between 4 and 9 weeks overall contrast sensitivity increased by a factor of 4-5 at all spatial frequencies. Beyond 9 weeks, contrast sensitivity at low spatial frequencies remained constant, while sensitivity increased systematically at higher spatial frequencies.
Norcia
A M
AM
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115.
Tyler
C W
CW
Hamer
R D
RD
D000328:Adult; D000375:Aging / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D010364:Pattern Recognition, Visual / Q000502:physiology; D011601:Psychophysics; D012684:Sensory Thresholds / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology