Modern Ophthalmic Lenses and Optical Glass.

Abstract

This work differs from other books on the same subject in that it is concerned chiefly with the various types of lenses and glasses which are at present available for filling the refractionist's prescriptions. The introductory chapters, which are short but adequate, deal with the history of glass, the manufacture of optical glass, the history of lenses and spectacles, the theory of lens action and the types of aberrations which occur in ophthalmic lenses. As Obrig notes, one reason for the high cost of lenses is the fact that only about 50 pounds (22.7 Kg.) of finished lenses are obtained from an original melt of 600 pounds (272.4 Kg.) of glass, while for certain types of bifocal lenses, only 12 (5.4 Kg.) pounds of finished lenses are obtained from the same original melt of 600 pounds. The succeeding chapters give brief but adequate descriptions of: (1) the properties and