The Eye, an Object and Rays: Seeing Past a Small Body
Ray diagrams asking why a small interposed body is seen better near than far
The verso is filled with ray diagrams of the eye: circles marking the pupil send out cones of lines toward distant objects, with a small body interposed between eye and object. The notes ask why the effect changes with distance, and argue that a body smaller than the pupil lets the images (species) pass and converge upside-down within the pupil, so the eye can still see the object beyond it. The reasoning turns on how far the small body must be moved for it not to block vision.
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Why the edges of an interposed body are read differently near and far
Leonardo asks why the effect occurs more from near than from far. He observes that the true extremities of the body set between the eye and the object are never entirely defined or made known by the pupil upon that distant object.
A body smaller than the pupil: images converge upside-down (a x d e y b)
A body interposed between eye and object that is smaller than the pupil causes the images to cross and converge upside-down within the pupil, so the object beyond is still seen. The farther such a small body sits from the eye, the farther it must be moved aside not to be seen, along the lettered rays a, x, d, e, y, b.