Eyesight is one of our most precious possessions, and it lets us enjoy our life to the fullest and appreciate the world around us. We use our eyes every day, but we don't think much about how they work. Written by two experts on the eye, Our Eyes and Our Vision explains the miracle of eyesight. You'll discover what can go wrong with your vision, how to prevent and cure problems, how ancient scholars treated ocular diseases, and what the future has in store for helping to protect and restore vision. Some eyesight problems can be prevented or corrected, but others can only be postponed. It's critical to understand the landscape so that problems can be avoided or addressed as soon as possible. You'll gain deep insights into how we see, and you'll also learn how we've gained knowledge about treating eye diseases over the years. Whether you are a nurse, ophthalmology assistant, emergency medical technician, or just an average reader wanting to protect and restore your eyesight, you'll be fascinated by Our Eyes and Our Vision. Our Eyes and Our Vision By Wolfgang H. Vogel Stephen E. Pascucci iUniverse, Inc. Copyright © 2011 Wolfgang H. Vogel, PhD, and Stephen E. Pascucci, MD All right reserved. ISBN: 978-1-4502-9198-9 Contents Introduction.................................................................................ixThe Structure of Our Eyes and Brain or a Wonder of Nature's Architecture.....................1The Basics of Our Visual Processes or How We Actually "See"..................................24Ocular Problems and their Corrections and Treatments.........................................62How to Take Care of Our Eyes.................................................................98History of Vision and the Healthy and Diseased Eye...........................................111The Vision of Animals........................................................................155A Look Into the Future.......................................................................178 Chapter One The Structure of Our Eyes and Brain or a Wonder of Nature's Architecture Eye sight or vision is a complicated process which needs the delicate structures of eyes but also muscles and nerves outside the eye to control their movements up and down as well as sideways. Furthermore, vision needs the brain because – as will be shown later – it occurs actually in the brain or "eye sight" is actually "brain sight". Thus, a basic understanding of the architecture of the eye and its associated muscles as well as that of the brain is necessary to comprehend later on the basic principles of our visual processes or how we see the world - and understand visual problems and diseases which can arise and how some of them can be prevented or even cured. Before driving a car it is necessary to understand that the steering wheel turns the car left or right and the accelerator or brakes speed up or slow down the vehicle. Thus, below is a basic but accurate description of most of the important structural features of the eye and brain necessary to understand and appreciate the wonders of our visual processes or our sight. The eye weighs about 7.5 g and is about 22 – 24 mm in diameter at adulthood. Looking at an eye, only the pupil, the colored iris and the white sclera which is covered by a transparent tissue called the conjunctiva are seen with the two eye lids around the eye. The area above the pupil and the iris is called the cornea which is also a transparent tissue. The eye lids with hairs at the edges consist of skin and muscles on the outside and the conjunctiva - a transparent thin tissue film - on the inside (as well as over the outside of the eye) so that we can blink. Each blink can be controlled by a conscious action but also occurs involuntarily or if we do not think about it. One eye blink lasts about 0.3 seconds and happens about every 5 seconds. Under the lids are various glands to produce tears and this tear film (actually the tear film consists of three major layers) keeps our eyes moist and lubricates them so that the eye lids can move smoothly over the eye. The tear film also supplies the cornea with oxygen. Each eye blink clears our eyes of small particles and microorganisms and reduces the risk of an infection. This tear film is constantly produced because it evaporates and drains through a channel on the inside of the eye into the nose. If the tear glands do not produce enough tears, the eye can become "dry" or a "dry eye" results. If the upper lids become too long they can partly cover our eyes and interfere with our vision. However, a cut through the eye or a cross section reveals a number of other important anatomical structures within the eye as can be seen in the picture below (do not be overwhelmed by all of these structures and names because they will be described and explained in detail later on): [ILLUSTRATION OMITTED] The eye or globe located in the eye socket or orbit c