Comparison of MRI slices through the optic nerves of a quail chick and an adult human, scaled so the slice areas are about equal. The optic nerves of all vertebrates cross at the optic chiasm, at midline behind the eyes near the mid-brain structures.

The zipper-like structure extending into the quail eye is a mystery to me. It appears to be an extension of the optic nerve into the retina (or what the retina develops from), but I've never seen an illustration of vertebrate eye development that shows anything like it. Another view of its structure can be seen in this surface rendering of the inside of the eyeball.

Exterior surface rendering and information about the quail chick data.

Information and volume data of human (me).



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