Shebiki Beaton

Yonnel Armstrong

Sunil Rupee

Dan Noel

Tomisha Madramootoo

Vrushika Gandhi

Dhanwanti Ramsaroop

• Appears at day 22 as a pair of shallow grooves on sides of forebrain• Grooves form outpocketings of forebrain, optic vesicles• Optic vesicles come in contact with surface ectoderm inducing lens

formation. Cells of surface ectoderm in contact with optic vesicle elongate and forms lens placode

• Lens placode invaginates and forms lens vesicle

• Optic vesicle invaginates and forms the double walled optic cup• Inner and outer layers initially separated by intraretinal space which later

disappears• Invagination at inferior surface forms the choroid fissure allowing hyaloid

artery (central artery) to enter the eye• At 7th week, lips of choroid fissure fuse and mouth of optic cup becomes the

pupil

• Outer layer- Pigmented layer

• Inner layer – Neural layer

– Posterior 4/5 Pars optica retinae

– Anterior 1/5 Pars ceca retinae

• Pars iridica retinae forms inner layer of iris

• Pars ciliaris retinae forms ciliary body

Development of the Retina

Layers of Pars Optica Retinae – Posterior 4/5 of Neural layer

• Layer of photosensitive rods and cones

• Outer nuclear layer

• Inner nuclear layer

• Ganglion cell layer

• Fibrous layer containing axons of nerve cells that form optic nerve

Parts of Pars ceca retinae- Anterior 1/5 of Neural layer

• Pars ciliaris retinae forms inner layer of iris– Iris formed from the pigmented

outer layer, unpigmentedinternal layer of optic cup and connective tissue containing pupillary muscles

• Pars ciliaris retinae– Markedly folded and covered

externally by mesenchyme that forms ciliary muscle

– Connected to lens by network of elastic fibers, the suspensoryligament

The iris, which extends partly over the lens, is composed of the two layers forming the edge of the optic cup and a layer of vascularized connective tissue containing the pupillary muscle.

During prenatal development, the anterior portion of the lens is covered by part of the pupillary membrane.

Prior to birth, the central part of the pupillary membrane, where the iris does not extend, degenerates to leave the pupil.

The pigmented layer of the iris is responsible for eye colour.

The ciliary body is formed from the two layers comprising the rim of

the optic cup, which undergo folding to form the ciliary processes.

Mesenchyme located at the edge of the optic cup gives rise to the

connective tissue of the ciliary body, the smooth muscle fibres of the

ciliary muscle and the suspensory ligaments of the lens.

The elastic fibres that make up the suspensory ligaments attach the

ciliary processes to the lens such that contraction of the ciliary muscle

will alter the curvature of the lens.

Development of the Lens

• At 5th wk, lens vesicle detaches from ectoderm and lies in mouth of optic cup

• Cells of posterior wall elongate and form the primary lens fibers that reach anterior wall at 7th

weeks• Secondary lens fibers added

to central core

The mesenchyme that surrounds the optic cup , excluding the anterior aspect where it forms the cornea, gives rise to the choroid and sclera.

The inner layer, immediately surrounding the pigment layer of the retina, is the choroid, which is a highly vascularized pigmented layer.

Blood vessels first appear in the choroid during the 15th week of development, and arteries and veins can be recognized by the 22nd week.

Part of the choroid develops into the cores of the ciliary processes.

At the posterior end of the optic cup, the choroid forms a sheath around

the optic nerve.

The outer layer, which surrounds the choroid, is the sclera. The sclera is

continuous with the substantia propria of the cornea.

It forms the tough, fibrous coat which surrounds the optic cup, as well as

a fibrous sheath surrounding the optic nerve.

The cornea is induced by the lens vesicle. The inductive influence

results in transformation of the surface ectoderm into the transparent,

multilayered avascular cornea,

The cornea is formed from three sources:

The external corneal epithelium, derived from surface ectoderm

The mesenchyme, derived from mesoderm, which is continuous with

the developing sclera

Neural crest cells that migrate from the lip of the optic cup and

differentiate into the corneal endothelium

The vitreous body forms within the cavity of the optic cup

It is composed of vitreous humor.

The primary vitreous humor is derived from mesenchymal cells of

neural crest origin. it is surrounded by a gelatinous secondary

vitreous humor.

The secondary vitreous humor consists of primitive hyalocytes

(vitreous cells), collagenous material, and traces of hyaluronic acid.

The optic cup is connected to the brain by the optic stalk, which has a

groove, the choroid fissure.

the choroid fissure closes (week 7) and a narrow tunnel forms inside

the optic stalk .

As a result of the continuously increasing number of nerve fibers, the

inner wall of the stalk grows, and the inside and outside walls of the

stalk fuse .

Cells of the inner layer provide a network of neuroglia that support the

optic nerve fibers.

The optic stalk is thus transformed into the optic nerve. Its center

contains a portion of the hyaloid artery, later called the central artery

of the retina.

On the outside, a continuation of the choroid and sclera, the

meninges surround the optic nerve

Transformation of the optic stalk into the optic nerve.

The eyelids develop during the sixth week from neural crest cell

mesenchyme.

The eyelids adhere to one another by the beginning of the 10th week

and remain adherent until the 26th to the 28th week .

While the eyelids are adherent, there is a closed conjunctival sac

anterior to the cornea. As the eyelids open, the bulbar conjunctiva is

reflected over the anterior part of the sclera and the surface

epithelium of the cornea.

The palpebral conjunctiva lines the inner surface of the eyelids.

There are 2 chambers:

Anterior

Posterior

The anterior chamber of the eye develops from a cleftlike space

that forms in the mesenchyme located between the developing lens

and cornea.

The mesenchyme superficial to this space forms the mesothelium of

the anterior chamber.

The lens induces the surface ectoderm to develop into the epithelium

of the cornea and conjunctiva.

The posterior chamber of the eye develops from a space that forms in

the mesenchyme posterior to the developing iris and anterior to the

developing lens.

the anterior and posterior chambers of the eye are able to communicate

with each other through a circumferential scleral venous sinus.

This vascular structure encircling the anterior chamber is the outflow site

of aqueous humor from the anterior chamber of the eye to the venous

system.

Develop from a number of solid buds from the surface ectoderm.

The buds branch and form the nasolacrimal ducts.

The lacrimal glands are small at birth and do not function fully until

approximately 6 weeks hence.

the newborn infant does not produce tears when it cries. Tears are often

not present with crying until 1 to 3 months.

Embryonic Structures Adult Derivative

Diencelpahlon

1. Optic Cup

2. Optic Stalk

Retina, iris , iris epithelium, dilator and

sphincter pupillae muscles of iris,

Ciliary body epithelium

Optic nerve (CN II), optic chiasm, optic

tract

Surface ectoderm Lens, anterior epithelium of cornea,

bulbar and palpebral conjunctiva

Mesoderm Sclera, choroid, stroma of iris, stroma

of ciliary body, ciliary muscle,

substantia propria of cornea, corneal

endothelium, vitreous body, central

artery and vein of retina, extraocular

muscles

Eye Abnormalities

• Failure of resorption during formation of the anterior chamber.

Failure of the choroid fissure to close.

Coloboma is a common eye

abnormality frequently associated

with other eye defects

absence of one eye

The lens becomes opaque

This may be causes by rubella

• In Micropthalmia, the eye is too small; the eyeball may be only two-

thirds of its normal volume. Usually associated with other ocular abnormalities, microphthalmia frequently results from intrauterine infections such as cytomegalovirus and toxoplasmosis

Synophthalmia

The eyes are fused because loss of midline structures prevented the eye fields from separating. Such babies also have severe cranial defects, including holoprosencephaly.

- http://en.wikipedia.org/wiki/Eye_development

- http://www.nature.com/nature/journal/v472/n

7341/fig_tab/472042a_F1.html

- http://www.lowvisionsolutions.com/resources/vi

sion-anatomy_eye.html

- Moore, K. & Persaud, T. (8th edition). The

Developing Human. Clinically Oriented

Embryology. The eye and Ear.

- Sadler, T. (11th edition). Langman’s Medical

Embryology. Eye.