Shalesh Kaushal

The neurosensory retina is a thin diaphanous structure, no thicker than tissue paper attached to the inner wall of the back of the eye. It is the photographic film of the eye and is a laminated integrated circuit that sub serves all aspects of visual perception including high resolution central acuity, motion detection, edge identification, contrast sensitivity, color identification and peripheral vision. It has at least nine identifiable structural layers, with at least 15 different cell types that carry out important metabolic functions. The maintenance of the structural and functional integrity of this highly organized tissue demands significant biological energy.

There are two major light absorbing photoreceptor cells in humans. The rod cells mediate peripheral and dim light vision and contain the visual pigment protein rhodopsin. These photoreceptors are found in largest numbers in the peripheral retina, but their highest density is in a circumferential distribution around the macula- the central region of the retina. The cone cells are important for color vision and high acuity central vision and are found predominantly in the macula. Not surprisingly, the retina is the most metabolically active tissue in the body per unit weight and the eye has the largest blood supply per unit weight in the human body. Thus, it serves as an excellent organ system to discuss and demonstrate energy metabolism, homeostasis, nutritional modulation and endogenous stem cell activity of disease states as well as canonical pathogenetic events (e.g. inflammation, oxidative stress, mitochondrial dysfunction, immune dysregulation) that lie central to so many chronic diseases.