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The Hunterian lectures on colour-vision and colour-blindness

Chapter 2: PREFACE
By F. W. Edridge-Green
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About This Book

These lectures present a physiological account of human colour vision and its disorders, beginning with retinal anatomy and the role of visual purple in rods and cones to convert light into neural impulses. The author outlines a retino-cerebral framework in which photochemical changes produce impulses whose character varies with wavelength, and argues that deficiencies in the colour-perceiving apparatus produce forms of colour-blindness ranging from dichromacy to reduced trichromacy. The text surveys entoptic phenomena, visual acuity and the evolution of the colour sense, then offers practical guidance for detecting colour-vision defects, describing test principles and instruments such as lantern and plate tests.

PREFACE

As there are many who are interested in the subject of vision and colour-blindness who are not acquainted with the structure of the eye, I will give a few details so that these persons may be able to consider the problem from the point of view of these lectures.

The eye is very similar to a photographic camera, and an actual image is formed on the back of the eye just as it is on the plate of the photographic camera or on the view-finder. The eye possesses a lens and also an iris which acts as an adjustable stop and regulates the size of the pupil. The membrane at the back of the eye upon which the image is formed is called the retina. The retina has several layers, but the sensitive layer consists of two elements called, from their shape, rods and cones. The problem therefore which has to be considered is, how is the light which forms the image on the sensitive layer of the retina transformed into visual impulses?

Those who are interested in the subject will find further details in my book on Colour-Blindness and Colour-Perception in the International Scientific Series. In that book there are three plates which show how the colour-blind see colours.

I have been annoyed to find that unauthorised persons have made lanterns professing to be mine but grossly inaccurate. The sole makers are those mentioned on page 53 in this book.

F. W. Edridge-Green.

The Institute of Physiology,
  University College,
    Gower Street, London.