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.<BR>This is the first 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.<BR>Volume I begins with an anatomical description of the eye and a discussion of physiological optics. It proceeds to an exposition of the dioptrics of the eye, with particular emphasis on optical imagery in a system of spherical refracting surfaces; blur circles on the retina; mechanism of accommodation; chromatic aberration in the eye; and illumination of the eye and the ophthalmoscope. Appendixes cover later findings on optical imagery, refraction, ophthalmoscopy, and other highly important topics; succeeding volumes examine the sensations and perceptions of vision.