PREFACE 



The reception accorded to my Textbook of Ophthalmology has per- 

 suaded me that there is a need for its continuation in a second edition. The 

 seven volumes of the Textbook took almost a quarter of a century to write, 

 a period unfortunately longer than it might have been owing to the exigencies 

 of war. The first four volumes have long been out of print — and inten- 

 tionally so because they have long been out of date. It is to be remembered 

 that the second volume was written before the suljjhonamides were intro- 

 duced ; the third before the antibiotics revolutionized the therapeutics of 

 infective diseases ; both of them before the role of viruses in ocular disease 

 was adequately appreciated ; the physiology of the eye of yesterday is 

 unrecognizable when compared with that of today ; even the anatomy has 

 been transformed by more elaborate optical and chemical methods of 

 investigation and the advent of the electron microscope. The re-writing of 

 the whole work if its com^^rehensive nature were to be retained would be an 

 immense task occupying more time than I could reasonably expect to have 

 at my disposal. Moreover, tomorrow ^^•ill be different from today, and if 

 a work such as this is to be of any lasting value it would seem to me desirable 

 that a new edition be published at least every fifteen or twenty years ; 

 fortunately, ophthalmology is no static science. 



It therefore seemed to me wise to sliare the task of re-writing the 

 original Textbook with my colleagues at the Institute of Ophthalmology in 

 London. I am grateful that they have accepted this burden. For this 

 reason I have changed the name of the book to a ''System of Ophthalmology " 

 since it will necessarih^ be less personal. 



This first volume in the new series is an extension of the first twenty 

 pages of Volume I of the old Textbook ; this I have %^Titten myself, largely 

 because it is a subject in which I am particularly interested — and I wished 

 to write it. The subject-matter has never been gathered together in a single 

 book before and it is my hope that it will interest ophthalmologists in so 

 far as it forms the basis of the science of vision ; and it may be that it will be 

 of value also to those whose interest is biological rather than clinical. ; 



The numerous marginal sketches are not usual in a book of this type. 

 To the student of natural history they may seem superfluous, but to the 

 ophthalmologist some of the animals may be unfamiliar and the drawings 

 may perchance add meaning to the zoological nomenclature and thus give 

 the text more life and interest. It is to be noted, however, that they are 

 drawn not to scale, but approximately to a standard size to fit into a 1-inch 

 margin, 



Stewart Duke-Elder. 



Institute of Ophthalmology, 



London, 



1957. 



