The most important work ever produced in the field of physiological optics, this classic is a model of scientific method and logical procedure, and it remains unmatched in its thorough and accessible approach. This is the third in a three-volume republication of the definitive English translation of Handbuch der Physiologischen Optik, originally published by The Optical Society of America in 1924 and containing everything that was known about physiological optics up until that time. The substratum consists of the data that Helmholtz furnished in the two nineteenth-century German editions that appeared during his lifetime. These volumes also contain extensive supplementary matter that Nagel, Gullstrand, and Kries incorporated in the third German edition of 1911, as well as significant new material prepared for the 1924 English translation by C. Ladd-Franklin, Gullstrand, and Kries, with copious annotations by James P. C. Southall that brought the work up to date with current research. Volumes I and II discuss the dioptrics of the eye and the sensations of vision;Volume III examines the perceptions of vision. Its topics include eye movements; the monocular field of vision; direction of vision; perception of depth; binocular vision; and many other highly important topics. Appendixes cover later findings on spatial configuration in vision and the theory of binocular instruments. Indexes for all three volumes are organized by subject and author.