Introduction

Optics is the study of light whereas visual optics is the study of the optical properties of the eye and sight. Ancient civilizations such as those of Greece were familiar with some of the properties of light, for example the laws of reflection. However, the Greeks misunderstood the nature of sight and the optical principles of the eye. They believed that light was emitted by the eye and only produced a visual response when the emitted rays struck an object. Many centuries passed before it was realized that light passes from the object to the eye and not from the eye to the object.

We will see later in this book, when we come to look at the optics of the eye, that the ability to sense the visual word around us is limited by the optical properties of the eye and its defects. For example before the advent of optical instruments, the smallest creature that could be seen with the unaided eye was about 0.05 mm in length and the mountains of the moon were unknown. Of particular frustration must have been the deterioration of eyesight with age. For example, as we age, the closest point of clear sight recedes, making it more and more difficult to do some things that we enjoy or need to do, such as reading and fine craft work. The discovery or invention of optical instruments enabled these restrictions to be overcome and allowed mankind to discover a world that was much more complex than ever envisaged, from the discovery of micro flora and fauna to countless galaxies far out in space.