| Main Anatomy Index | Eye
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Last updated 30 March 2006
This page was contributed by David
Development of the optic cup
- By day 24, the optic vesicles have evaginated from the
diencephalic region of the neural tube, with their distal surfaces, the retinal
discs, apposed to the inner surface of adjacent ectoderm.
- On day 32, the retinal disc indents to form the goblet shaped optic
cup that will eventually form the retina, whist the optic vesicle has narrowed
into a thin optic stalk and is the beginnings of the
- On the ventral surface of the optic cup, the choroidal fissure
transmits the hyaloid vessels into the interior of the
Development of the lens
- Meanwhile, a thickening called the lens placode
develops in the surface ectoderm as a result of induction by the adjacent optic vesicle.
- Whilst the optic cup forms, the lens placode invaginates, forming a lens
pit, and then pinches off from the surface ectoderm to form the lens vesicle, sitting within the rim of the optic cup.
- Between the lens vesicle and the inner wall of the optic cup, the lentiretinal
space, a gelatinous matrix is secreted, which will form the vitreous
- On day 33, the cells of the posterior wall of the lens
vesicle differentiate into primary lens fibres, filling
up the lumen of the lens vesicle, and will make up the central lens body of the mature
- Cells on the anterior wall of the lens vesicle
differentiate into a simple epithelium, and in the 8th week, cells at the
periphery of this epithelium differentiate into secondary lens
- Both the lens and retina are supplied by the hyaloid
branch of the opthalmic artery, which occupies the lentiretinal space in foetal life, but
the mature lens loses its blood supply, so part of the hyaloid vessels degenerate, leaving
the hyaloid canal in the vitreous body.
- The lips of the choroidal fissure fuse to enclose the portions of the hyaloid vessels in
the optic stalk, transforming them into the central artery
and vein of the retina.
Development of the neural and pigment retinas
of the retina
Outer wall of optic cup
Melanin appears on day 33
Inner wall of optic cup
Mostly developed by week nine,
All layers present by 8 months
Development of the neural retina
- The layer of cells adjacent to the lumen of the optic cup becomes the outer
proliferative zone, producing waves of cells the migrate inward toward the
lentiretinal space, forming the layers of the neural retina in a similar fashion to the
ventricular epithelium of the neural tube.
- By the 9th week, there are 2 layers of blast cells:
The inner neuroblastic layer, producing the ganglion and supporting cells.
- The outer neuroblastic layer, producing the
light-receptive rod and cone cells
- On the inner surface of the retina, axons grow from the ganglion cells to form the fibre layer
- 2 thin membranes bound the neural retina:
- The internal limiting membrane, separating the fibre
layer from the vitreous body
- The external limiting membrane, just external to the
rod and cone cell bodies.
- The space between the neural and pigment retinas, the intraretinal
space, is an extension of the 3rd ventricle, and is obliterated by
growth, disappearing in the 7th week as the retinal
Development of the optic nerve
- In the 6th week, axons from the retinal ganglion cells reach and grow along
the optic stalk to form the optic nerve (CN II), with
axons on the nasal side of each retina crossing to the contralateral side at the optic chiasm, and finally, all axons synapsing in the lateral geniculate bodies of the diencephalon.
Development of the mesenchyme around the eye
- In the 6th week, the mesenchyme encapsulating the optic cup forms the inner,
vascular choroid, and the outer, fibrous sclera.
- In the 6th week, the mesenchyme anterior to the lens splits into layers
conforming to the choroid and sclera to form the anterior chamber of
- The mesoderm of the anterior wall of the anterior
chamber, with surface ectoderm, forms the cornea, consisting of 3 layers:
- The superficial anterior epithelium, from surface
- The substantia propria, from the mesoderm of the
- The epithelium lining the anterior chamber, from the
mesoderm of the anterior wall
- The mesoderm of the posterior wall of the anterior
- The posterior chamber of the eye, via vacuolisation of
the posterior layers of mesoderm in contact with the lens
- The pupil of the eye, after the breakdown of a thin
layer of remaining mesoderm called the pupillary membrane
that initially separated the posterior and anterior chambers.
- The anterior rim of the optic cup, with overlying choroid, forms the iris,
with its posterior surface coming from the 2 fused layers of the optic cup, and the pupillary muscle (sphincter and dilator pupillae) derived from neural crest origin.
- Just posterior to the iris, the optic cup forms the ciliary body,
including the suspensory ligament, and the ciliary muscle, which comes from neural