Here is a pretty good labeled diagram of the human eye. https://en.wikipedia.org/wiki/File:Eye-diagram_no_circles_border.svg Labels for the numbers of the different parts are further down on the page. From inside out there is the retina and then right next to it the choroid, which is layers of blood vessels. You can see some of these blood vessels, through the retina, very clearly by pictures taken of the back-side of the eye, taken through the pupil with front-side illumination (I have quite a collection of similar pictures that I keep at my doctor's office, which rival my Babylon 5 playing card collection!). Here is a pretty good picture of it: https://www.123rf.com/photo_7400110...e--showing-retina-optic-nerve-and-macula.html That the choroid can affect and plays a part in what a person sees is documented here: https://en.wikipedia.org/wiki/Choroid Under the paragraph "Mechanism" it talks of the effects of light reflection within the choroid layer (behind the retina). It is interesting to read that that is a cause of the "redeye" effect in photographs, and the "light-shine" effect that you see in some animal's eyes, for instance cat eyes. So, all of this is to show that the anatomy of the eye is complex, and how light rays interact in the eye is complex too.