Introduction by Helga Kolb


Helga Kolb

Our eyes are marvellous sense organs that allow us to appreciate all the beauty of the world we live in, to read and gain knowledge, and to communicate our thoughts and desires to each other through visual expression and visual arts.







Vision is the most fundamental of our senses and it is perhaps the greatest tragedy of all when blindness robs us of this modality. Although all parts of the eye are important for perceiving a good image, the most vital layer for vision is the retina. The retina is essentially a piece of brain tissue that gets direct stimulation from the outside world’s lights and images.

Understanding the organization of the vertebrate retina has been and still is the goal of many talented visual scientists over the years. Ramon y Cajal in the 19th century presented the first comprehensive anatomic descriptions of the neural cell types that constitute the retina in a number of vertebrate species. There then followed an understanding of the role of visual purple in photochemistry of photoreceptors and important psychophysical studies on image formation, light and dark adaptation and color vision.







By the middle of the 20th century, though, we were beginning to need detailed information of the biophysics, biochemistry and neuroanatomy of circuits that underlie these functions. Newer techniques such as electron microscopy, microelectrode recording, immunostaining and pharmacology allowed us a very rapid advancement of knowledge on the organization of the retina and visual system.



In the present century we have advanced knowledge of the retina in the areas of molecular biology, evolution and development with stunning new visualization techniques. The purpose of this Electronic Tutorial is to summarize our present understanding of the field, based primarily on anatomical and physiological investigations. Over time we have invited famous authors to write chapters on their speciality concerning the retina and higher visual pathways. We also attempt to add clinical research findings in cell biology and genetics of retinal diseases. A great addition has been a section on Psychophysics of Vision which we hope will be of general information to all interested in learning the basics of visual perception.

We have tried to present material at the cutting edge of the present knowledge, but in a simple way that is accessible to both student, professional and non-expert people.

An additional chapter on How The Retina Works is available here (1.8MB pdf file).

If you have questions, suggestion for improvements, or other useful comments, do not hesitate to contact us at the following addresses: or


Updated November, 2013

Helga Kolb