Explanation

Cornea. Human eye ball is enveloped by three layers, i.e., sclerotic layer, choroid layer and retinal layer outermost sclerotic layer is white portion of eye which mergas with transparent round window called cornea in center. Middle choroid layer lie close to retina and contain light absorbing pigments. In front it form celeary body, which is hidden by iris. Retinal, the innermost thin transparent appear purplish due to presence of eye pigment-rhodopsin