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 the goal of many talented visual scientists during the past 100 years. With Cajal's (1892) anatomic descriptions of the cell types that constitute the retina in a number of vertebrate species, and with an early understanding of the role of visual purple in photochemistry in combination with psychophysical studies of adaptation and color vision, we had in the sixties the rudiments of an understanding of how the retina might be organized and functioning. 
To go further, though, we were beginning to need detailed information of neural circuits that underlie these functions. It was the advent of electron microscopy, microelectrode recording techniques, and pharmacology that then allowed us an era of very rapid advancement. The purpose of this Electronic Tutorial is to summarize these recent advances and to describe our present understanding, based primarily on anatomic investigations, of the Neural Organization of the Mammalian Retina. As time goes on we have been inviting other authors to write chapters on their speciality concerning the retina or other visual pathways. 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 expert and non-expert people.
If you have questions, suggestion for improvements,.... do not hesitate to contact us at the following addresses:
Dr. Helga KolbDr. Eduardo Fernandez
E.Fernandez@umh.es
Dr. Ralph Nelson
rnelson@codon.nih.gov
Updated: February, 2001