Transverse section showing the lens and the optic cup.

The eye develops from the neural tube and the epidermis. This development is an example of sequential inductions where the organ is formed from two different tissues. First, there is an outpocketing of the neural tube called optic vesicles. The optic vesicles come into contact with the epidermis and induce the epidermis. The epidermis thickens to form the lens placode. The lens differientiates and invaginates until it pinches off from the epidermis. The lens acts as an inducer back to the optic vesicle to transform it into the optic cup and back to the epidermis to transform it into the cornea. The optic cup then delaminates into two layers: The neural retina and the pigmented retina. In the developing vertebrate nervous system, the neural tube is the precursor of the central nervous system, which comprises the brain and spinal cord. ... Look up Epidermis in Wiktionary, the free dictionary. ... The eyes begin to develop as a pair of diverticula from the lateral aspects of the forebrain. ... The outer wall of the bulb of the optic vesicles becomes thickened and invaginated, and the bulb is thus converted into a cup, the optic cup (or ophthalmic cup), consisting of two strata of cells). ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ...

Only the epidermis in the head is competent to respond to the signal from the optic vesicles. Both the optic vesicle and the head epidermis are required for eye development. The competence of the head epidermis to respond to the optic vesicle signals comes from the expression of Pax6 in the epidermis. Pax6 is necessary and sufficient for eye induction. This competenece is acquired gradually during gastrulation and neurulation from interactions with the endoderm, mesoderm, and neural plate. 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... Neurulation is a part of organogenesis in vertebrate embryos. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... The neural plate is thick and flat bundle of ectoderm which develops in the embryo into the nervous system. ...

Sonic hedgehog reduces the expression of Pax6. When Shh is inhibited during development, the domain of expression for Pax6 is expanded and the eyes fail to separate causing cyclopia. Overexpression of Shh causes a loss of eye structures. Sonic hedgehog homolog (SHH) is one of five proteins in the vertebrate hedgehog (HH) family thus far described, the others being desert hedgehog (DHH), Indian hedgehog (IHH), echidna hedgehog (EHH) and tiggywinkle hedgehog (TwHH). ... Cyclopia, a medical disorder characterized by the fusion of the orbits into a single cavity containing one eye. ...