The second section is devoted to geometric optics, treating of mirrors, lenses, prisms, and aberrations. In these chapters, the author deals with the fundamental problems which eventually allow the ophthalmologist to have an intelligent approach to the practice of clinical refraction. Geometric optics is developed as a useful tool for understanding the process of vision. A clear discussion of the mode of operation of the plane mirror emphasizes that this is not an image-forming mechanism but rather a means for changing the direction of light rays as contrasted to curved mirrors which form an image, a fact many times entirely neglected in introductory physics texts. Refraction problems are studied through single interface spherical lenses, thick lenses, thin lenses, cylindric and toric lenses, prisms and prismatic effect of lenses. Quite naturally these topics lead to those pertaining to aberrations, their causes, effects, and means available for correction. These chapters should be of especial interest to designers of optical systems. In conformance with general opthalmological practice, the unit of power used is the diopter and all computations are so carried out.
The eye as an optical instrument and as a biologic entity is the subject of the last section. A review of the history of measurements of the physical optical characteristics of the eye shows how such things as the focal points of the eye and the equivalent planes are determined. The elements of refraction using correction lenses are illustrated in sample problems for the cases of axial myopia and axial hyperopia.
This reviewer found the informal style most exhilirating, almost as if the author were actually present discussing the subject matter.