Definition of retina

The word "retina" originally derives from the Latin word "retinae" which means "net" or "veil." In ancient anatomy, the retina was mistakenly believed to be a membrane, like a net, that covered the back of the eye and impelled light into the brain. The concept of the retina as a membrane was proposed by the ancient Greek physician, Galen, in the 2nd century AD. He observed that insects had small, transparent membranes at the back of their eyes and incorrectly assumed that a similar structure existed in human eyes. Galen's theory was widely accepted by subsequent anatomists until the 16th century when scientist Andreas Vesalius proved that the retina was actually a layer of cells lining the back of the eye. The word "retina" continued to be used in the medical field, but with a different meaning. As our understanding of anatomy evolved, scientists came to recognize that the retina is a delicate layer of neural tissue that contains specialized cells, including photoreceptors, that are responsible for converting light into electrical signals, which are then transmitted to the brain. The retina is now considered to be an essential structure of the eye, rather than just a covering or membrane as traditionally believed in ancient times.