Overview

Abstract

Vision is our dominant sense. The eyes, specialized for the detection of light, are our most important sensory organs, providing approximately 70–80 % of our total sensory information. The optical apparatus projects an image of our environment onto the back of the eye covered by the retina. The retina is a neuronal tissue originating from the brain during embryonic development and is, thus, a true part of the central nervous system. The retina is a well-layered, appr. 200 μm thick tissue and can be divided into an outer part that harbors the light-sensitive cells – the rod and cone photoreceptor cells – and an inner part that comprises a neuronal network [1]. This network performs the first steps of information processing before the signal is relayed by the retinal ganglion cells to the brain via the optic nerve. A human retina harbors around 120 million rod and 6 million cone photoreceptor cells. Rods are highly sensitive, can respond to single light quanta, and provide vision during night and at twilight. Cones are less sensitive and provide color vision during daylight. Behind the retina, two more layers are located: the retinal pigment epithelium (RPE) and the choroid (see Fig. 1), a dense network of blood capillaries, which provides nutrients and oxygen to the photoreceptors. Both are separated by Bruch’s membrane, an elastin- and collagen-rich structure [2].