The first edition of this book was written prior to 1991 and it seemed appropriate to revise and update the text in view of the rapid expansion in information which has occurred in the last decade. Furthermore, in the first edition, the reproduction of some of the illustrations was not of sufficient standard to be of value to the reader. Accordingly some of the inadequate figures have been replaced by colour figures which have been inserted into the text. Colour has also been included because many histopathological illustrations, e. g. special stains such as Gram, PAS, trichrome stains etc. , and immunohistochemical reactions, are much better appreciated. With regard to references, I have taken advantage of the currently available access to all the medical literat ure, which is what I anticipate will be the course of action of the reader. Glasgow, 2001 Acknowledgements It is a pleasure to re cord the support I have received in the last decade from Professors Wallace Foulds, Colin Kirkness and Gordon Dutton and from Mr Bertil Damato in their continuing efforts to educate me in the subtleties of clinical ophthalmology. I am particularly indebted to Dr Sarah Coupland who provided the information on lymphoid neoplasia which is included in this book and I must thank Dr Weng Sehu who established the computer equipment which has been so valuable in the preparation of the new illustrations.