Eye - Derivatives of Surface Ectoderm

1. The eye develops as the result of an interaction between the surface epithelium of the embryonic head and an evagination of the diencephalon (forebrain) called the optic vesicle.
2. The head ectoderm is made competent to form a lens by a series of inductive interactions during early development.
3. When the optic vesicle contacts the head ectoderm, it sends inductive signals that cause the epithelium to thicken and form a placode.
4. The lens placode invaginates, pinches off from the surface and goes on to differentiate as the lens. The optic vesicle bends round it and forms the bi-layered optic cup.
5. The outer layer of the optic cup differentiates to form the retinal pigment epithelium (RPE). The inner layer forms all the cells of the neuronal retina (photoreceptors, bipolar, amacrine, horizontal, ganglion cells etc.).
6. The iris and ciliary body develop from the distal tip of the retina.
7. The lens is responsible for inducing and organising the development of the cornea, iris and ciliary body.

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