FORMATION OF LENS VESICLE
The optic vesicle grows laterally and comes in contact
with the surface ectoderm. The surface ectoderm,
overlying the optic vesicle becomes thickened to form
the lens placode (Fig. 1.6A) which sinks below the
surface and is converted into the lens vesicle (Figs.
1.6 B&C). It is soon separated from the surface
ectoderm at 33rd day of gestation (Fig. 1.6D).
FORMATION OF OPTIC CUP
The optic vesicle is converted into a double-layered optic cup. It appears from Fig. 1.6 that this has
happened because the developing lens has invaginated itself into the optic vesicle. In fact conversion of the optic vesicle to the optic cup is due to differential growth of the walls of the vesicle.
The margins of optic cup grow over the upper and lateral sides of the lens to enclose it. However, such a growth does not take place over the inferior part of the lens, and therefore, the walls of the cup show deficiency in this part. This deficiency extends to some distance along the inferior surface of the optic stalk and is called the choroidal or fetal fissure
In the posterior part of optic cup the surrounding
fibrous mesenchyme forms sclera and extraocular
muscles, while the vascular layer forms the choroid
and ciliary body.
The optic vesicle grows laterally and comes in contact
with the surface ectoderm. The surface ectoderm,
overlying the optic vesicle becomes thickened to form
the lens placode (Fig. 1.6A) which sinks below the
surface and is converted into the lens vesicle (Figs.
1.6 B&C). It is soon separated from the surface
ectoderm at 33rd day of gestation (Fig. 1.6D).
FORMATION OF OPTIC CUP
The optic vesicle is converted into a double-layered optic cup. It appears from Fig. 1.6 that this has
happened because the developing lens has invaginated itself into the optic vesicle. In fact conversion of the optic vesicle to the optic cup is due to differential growth of the walls of the vesicle.
The margins of optic cup grow over the upper and lateral sides of the lens to enclose it. However, such a growth does not take place over the inferior part of the lens, and therefore, the walls of the cup show deficiency in this part. This deficiency extends to some distance along the inferior surface of the optic stalk and is called the choroidal or fetal fissure
In the posterior part of optic cup the surrounding
fibrous mesenchyme forms sclera and extraocular
muscles, while the vascular layer forms the choroid
and ciliary body.
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