VISUAL OPTICS AND RETINAL CONE TOPOGRAPHY IN THE COMMON MARMOSET (CALLITHRIX-JACCHUS)

The common marmoset (Callithrix jacchus) is a small, diurnal, New Worl d monkey amenable to vision research. In this paper we describe the vi sual optics and cone photoreceptor topography of the normal adult marm oset. Paraxial optical ray-tracing shows that the marmoset eye is well represented as a scaled-down version of the human eye. The density of foveal and perifoveal cone photoreceptors in the marmoset is as high, and in peripheral retina higher, than those reported in humans and ma caques. The foveal acuity predicted by the Nyquist limits set by the c one mosaic (30 c/deg) is in agreement with behavioral measures of visu al acuity. Foveal depth of focus is remarkably small (< 0.2 D) for an eye of this size (axial length about 11 mm). Estimates of the amplitud e of accommodation using infrared photorefraction indicate that the ma rmoset is capable of more than 20 D of accommodation.