This book is designed to be a pictorial guide to ophthalmology and not a comprehensive textbook. It includes chapters on anatomy, physiology and optics to explain the simple elements of the basic sciences that are needed to understand ophthalmology. The section on examination describes the common investigations in an eye department in the hope that reports from ophthalmologists may become more easily understood. The clinical chapters represent 5 years of ophthalmic referrals by local family doctors in a part rural and part suburban area. This selection of eye disease therefore excludes some of the rare conditions, but includes those common problems that can worry not only the busy family doctor, but also the hard pressed medical student. 7 Anatomy and Physiology The sense of vision depends on the integrity of a set of Internal Eye anatomical and physiological factors, a study of which The eye consists of three concentric layers. The outer­ will simplify the understanding of ocular disease. most fibrous sclera is opaque and accounts for five sixths of the globe. It is continued anteriorly into the External Eye transparent cornea. The middle vascular coat or uveal The eyeball lies in the anterior part of the orbit, which tract is made up of the choroid, ciliary body and iris. is approximately pyramidal in shape. The bony orbital The innermost layer is the light sensitive retina formed margin, which outlines the base of the pyramid, affords embryologically from the forebrain vesicle (Figure 3).