Pb. Kruger et al., ACCOMMODATION RESPONDS TO CHANGING CONTRAST OF LONG, MIDDLE AND SHORTSPECTRAL-WAVEBAND COMPONENTS OF THE RETINAL IMAGE, Vision research, 35(17), 1995, pp. 2415-2429
We simulated the effects of longitudinal (axial) chromatic aberration
and defocus on contrast of the long-, middle- and short-wavelength com
ponents of the retinal image to determine whether the effects of chrom
atic aberration are sufficient to drive accommodation. Accommodation w
as monitored continuously while subjects (12) viewed a 3 c/deg white s
ine-wave grating (0.92 contrast) in a Badal stimulus system. The contr
asts (amplitudes) of the red, green and blue components of the white g
rating changed independently to simulate a grating oscillating from 1
D behind the retina to 1 D in front of the retina at 0.2 Hz. Subjects
responded strongly to the chromatic simulation but poorly to a luminan
ce control. The results support the hypothesis that focus is specified
by the contrast of spectral-wavebands of the retinal image, and that
conventional color mechanisms, monitoring chromatic contrast at lumina
nce borders (1-8 c/deg), mediate the signals that specify dioptric ver
gence.