Binocular Vision and Ocular Motility

Binocular vision is one of the hallmarks of the human race that has bestowed on it the supremacy in the hierarchy of the animal kingdom. It is an asset with normal alignment of the two eyes, but becomes a liability when the alignment is lost. Binocular vision develops because the brain is able to fuse the separate images from each eye into a single image. This is aided by the ocular muscles that function to ensure both eyes look directly at the same object. One of the most important features of this ability is that it gives an indication of the depth of field of view and the ability to judge distances. The extraocular muscles are located within the orbit, but are extrinsic and separate from the eyeball itself. They act to control the movements of the eyeball and the superior eyelid. The levator palpebrae superioris (LPS) is the only muscle involved in raising the superior eyelid. A small portion of this muscle contains a collection of smooth muscle fibres – known as the superior tarsal muscle. In contrast to the LPS, the superior tarsal muscle is innervated by the sympathetic nervous system. The brainstem provides the main motor and sensory nerve supply to the face and neck via the cranial nerves. Of the thirteen pairs of cranial nerves, ten pairs (or twelve, if the diencephalon is included in the brainstem) come from the brainstem. The brainstem is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brainstem. The oculomotor nerve originates from the third nerve nucleus at the level of the superior colliculus in the midbrain. The third nerve nucleus is located ventral to the cerebral aqueduct, on the pre-aqueductal grey matter. This book continues to be the most complete discourse and reference on strabismus and ocular motility. This book presents elements of binocular vision and ocular motility.