MESENCHYME CHANGES IN

The developing neural tube (from which central nervous system develops) is surrounded by
mesenchyme, which subsequently condenses to form meninges. An extension of this mesenchyme also
covers the optic vesicle. Later, this mesenchyme differentiates to form a superficial fibrous layer
(corresponding to dura) and a deeper vascular layer (corresponding to pia-arachnoid) .
With the formation of optic cup, part of the inner vascular layer of mesenchyme is carried into the cup
through the choroidal fissure. With the closure of this fissure, the portion of mesenchyme which has
made its way into the eye is cut off from the surrounding mesenchyme and gives rise to the hyaloid
system of the vessels (Fig. 1.9). The fibrous layer of mesenchyme surrounding the anterior part of optic cup forms the cornea. The corresponding vascular layer of mesenchyme  becomes the iridopupillary membrane, which in the peripheral region attaches to the anterior part of the optic cup to form the iris. The central part of this lamina is pupillary membrane which also forms the tunica vasculosa lentis .