The optic chiasm.

In the first part of this chapter the anatomy and vascular supply of the chiasm are recounted, and the visual symptoms that may arise in chiasmal disease are noted. The neuro-ophthalmic signs, including the pattern of visual field defects, appearance of the optic disc, and various uncommon clinical accompaniments, are described. The second part deals with a comprehensive list of disease processes that may directly or indirectly affect the chiasm. These are divided into inflammatory disorders, including sarcoidosis, multiple sclerosis, and idiopathic chiasmitis; infective disorders, including tuberculosis; and a large section on tumors, including pituitary adenomas, cysts, and choristomas, malignant disorders, including germ cell tumors and glioma, and meningioma; and finally vascular disorders and compression due to hydrocephalus. In each case the clinical features and management of the disorder are noted, as well as the prognosis for visual improvement following treatment.