The Oculomotor Systems-Cranial Nerves III, IV And VI

In this chapter we will discuss the organization of the ocular motor system and how visual information guides eye movements.  This review will inclucde the function of the six extraocular muscles, the neuronal control systems, which keep the fovea (that part of the retina responsible for sharp vision) on the object of interest, the neuronal systems for saccadic eye movements (they shift the fovea rapidly to a visual target in the periphery of the visual field), and the neuronal systems, which control smooth pursuit (keeps the image of a moving target on the fovea), vergence (move the eyes in opposite direction so the image is still and stablizes the image when the object moves or when the head moves), vestibulo-ocular movements (these hold images still on the retina during brief movements and are under the control of the vestibular system), and optokinetic movements (these hold images during sustained head rotation and are driven by visual stimuli).  We will review disorders of the neuromuscular junction and their effect on ocular muscles, as well as some of the myopathies which involve ocular muscles.  We will first review the morphogenesis of the CNS to gain some understanding of the origin of the cranial nerves (CN) III, IV, and VI and the extraocular muscles.

The oculomotor systems CN III, IV, & VI