"Now, it is true that the eyes receive in them pictures of all the objects which are placed before them, just as the tablets of painters receive the images of things which are painted on them; and it is also true that these images are in many respects like the objects from which they proceed. But in what does the resemblance consist? It does not consist in the fact that these images are colored or that they have any other resemblance to the objects we see. For those pictures which the tablets of painters receive are in the form of the things which are painted on them, and are colored in the same manner as these things. Whereas the pictures which are formed in the eyes are only a certain disposition of the parts of the brain which represent the things we see, without resembling them either in color or in any other property, except in so far as they represent the size, shape, and situation of these things, and in so far as they dispose the mind to perceive the same objects as these things represent" (source: "Dioptrique," Part Five, Article 17).
---"We must observe that all the rays which issue from any point of the object and traverse the aperture of the pupil, go to form an image of that point in a certain part of the bottom of the eye, which is called the retina; and all the images of the several points are there arranged in the same order as the points themselves in the object from which they proceeded. Now this arrangement is so precise that a painter could not more accurately depict all the objects of a landscape on a small piece of canvas than nature does in the eye on this small part of its bottom, which is less than the third of a line in breadth, and it even depicts them better, for in painting there will always be found certain things which, although they may appear to the eye exactly similar to what they represent, will nevertheless, when examined closely, appear different, whereas in the eye no such differences can ever be found" (source: "Dioptrique," Part Two, Article 8).
---"It has sometimes doubtless happened to you, while walking in the night without a torch through places which are a little difficult, that it became necessary to use a stick in order to guide yourself; and you may then have been able to guide yourself; and you may have been able to notice that you felt, through the medium of this stick, the diverse objects placed around you, and that you were even able to tell whether they were trees, or stone, or sand, or water, or grass, or mud, or any other such thing. True, this sort of sensation is rather confused and obscure in those who do not have much practice with it: but consider it in those who, being born blind, have made much use of it all their lives, and you will find it so perfect and so exact that one might almost say that they see with their hands, or that their stick is the organ of some sixth sense given to them in the place of sight. And in order to draw a comparison from this, I would have you consider light as nothing else, in bodies that we call luminous, than a certain movement or action, very rapid and very lively, which passed toward our eyes through the medium of the air or other transparent bodies, in the same manner that the movement or resistance of the bodies that this blind man encounters is transmitted to his hand through the medium of his stick."" (Found in: Darrigol, Oliver. A History of Optics. Oxford University Press, 2012, pp. 39-20.)