Introduction

The highly distilled knowledge represented in this chapter took centuries for the early Greek and later Arabic scholars to develop. Enormous efforts were made especially during the middle ages to transmit this knowledge from the Ancients by providing translations from Greek into Arabic and Latin, and later into the other languages of Western Europe (Lindberg, 1978a).

The issues that had to be argued about, thought through, and developed for about two millennia were extraordinarily basic, such as the rectilinear propagation of light; the structure and position in the eye of the sentient surface leading to perception; the nature of refraction, especially within the eye; vision due to extramission of radiation from the eye vs. intromission of light from objects into the eye; that light emanates in all directions from each point on an object; and that the relationships between points on an object had to be maintained in the image within the eye. It was not until 1583 that Felix Platter, a medical peer of Johannes Kepler, correctly placed the visual sensory mechanism in the retina and not at the lens (Lindberg, 1976, 191–208). Armed with this insight, in 1604 Kepler provided the correct refractive path of light through the cornea, pupil, lens, and all refracting media; offered the correct theory of the inverted, reversed retinal image; and demonstrated how all light rays emanating from a point in the visual field are brought to a focus at one point on the retina (Lindberg, 1976, 1978b).

In the context of oculomotor systems, it is recognized that visual stimulation plays a large, but not unique, role in the control of eye movements.