ABSTRACT
The most familiar representation of image formation in an excised eye is that from Descartes's Dioptrique, in which the cosmic observer ponders on the spatial arrangement of the inverted and reversed retinal image. The armory of techniques for probing the workings of the visual system has been extended so that the operation of the whole working brain can now be imaged. Despite the fact that visual artists and visual scientists are often concerned with examining similar phenomena, the methods they adopt differ radically. The axons from the ganglion cells travel to the visual cortex, undergoing partial separation so that the left and right hemiretinae project to opposite hemispheres; however, there is some projection to both hemispheres for fibers from the vertical midline of the retina. The illusions that attracted the interests of many nineteenth-century visual scientists were those labeled "geometrical optical" by J. J. Oppel.
