The cornea is that the transparent a part of the eye that covers the front portion of the eye. It covers the pupil (the opening at the middle of the eye), iris (the colored a part of the eye), and anterior chamber (the fluid-filled inside the eye). The cornea's main function is to refract, or bend, light. The cornea is liable for focusing most of the light that enters the eye. The cornea consists of proteins and cells. It doesn't contain blood vessels, unlike most of the tissues within the human body. Blood vessels may cloud the cornea, which can prevent it from refracting light properly and should adversely affect vision. Since there are not any nutrient-supplying blood vessels within the cornea, tears and therefore the aqueous humour (a watery fluid) within the anterior chamber provide the cornea with nutrients. The cornea is comprised of 5 layers: the epithelium, Bowman's layer, the stroma, Descemet's membrane, and therefore the endothelium. the primary layer, the epithelium, may be a layer of cells covering the cornea. It absorbs nutrients and oxygen from tears and conveys it to the remainder of the cornea. It contains free nerve endings. It also prevents foreign matter from entering the eye.