cornea

the outermost, exposed layer of the EYE , which is transparent and lies over the IRIS and LENS . It refracts light entering the eye, directing the rays to the lens and thus acting as a coarse focus. It is a layer of CONNECTIVE TISSUE that has no blood supply of its own but is supplied with nutrients from the aqueous humour within the eye. It is highly sensitive to pain, and presence or absence or response if the cornea is touched is used as an indicator of a person's condition, e.g. in a comatose patient.