SINCE the issue of the first volume of the Saunders Question-Compends, OVER 200,000 COPIES of these unrivalled publications have been sold. This enormous sale is indisputable evidence of the value of these self-helps to students and physicians. ESSENTIALS OF REFRACTION AND OF DISEASES OF THE EYE WITH A CONSIDERATION OF Ocular Injuries and the Ocular Symptoms BY EDWARD JACKSON, A.M., M.D. Emeritus Professor of Diseases of the Eye in the Philadelphia Polyclinic; Formerly THIRD EDITION, REVISED AND ENLARGED 82 ILLUSTRATIONS PHILADELPHIA AND LONDON W. B. SAUNDERS & COMPANY 1901 16295 COPYRIGHT, 1901, By W. B. SAUNDERS & COMPANY. Registered at Stationers' Hall, London, England. ELECTROTYPED BY PRESS OF W. B. SAUNDERS & COMPANY. PREFACE TO THE THIRD EDITION. THE favor accorded to preceding editions of this work seems to justify its careful revision and extension. The added pages of the present edition have given space to make it more complete and more symmetrical than was possible in the earlier editions. The injuries of the eye by traumatism and the ocular symptoms and lesions of general diseases have now been given a consideration proportioned to the great importance they assume in the work of the general practitioner, and it is believed that such of the recent advances in ophthalmology as properly come within the scope of a work of this character have been duly noticed. While the application of the tests of vision required in the Army, Navy, and railway services, or in the public schools, is not the usual work of the medical practitioner, some knowledge of these tests is popularly expected of him. The account of them here introduced goes sufficiently into detail to enable the reader to apply them. At the same time the original plan and method of the work have been closely adhered to. As before, a fair acquaintance with the general principles and facts of medicine and surgery is presumed, and, starting from this, the attempt is made to introduce the student to the essentials of this branch. It is |