Abstract
It is often claimed that the human retina is poorly designed because it appears to be placed in the eye backwards. Its design, therefore, requires that light travel through the nerves and blood vessel to reach the photoreceptor cells located behind the eye's wiring. We now know that specific functional reasons exist for this so-called backward placement of the photoreceptors. A major reason for the retina reversal is that it allows the rods and cones to interact with the retinal pigment epithelial cells that provide nutrients to the retina, recycle photopigments, provide an opaque layer to absorb excessive light, and perform other functions. This design is superior to other systems, because it allows close association with the pigmented epithelium required to maintain the photoreceptors. It is also critical in both the development and normal function of the retina.