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DEVELOPMENT OF EYE

LECTUREBY

PROF. ANSARI11-05-09, MONDAY, 1.30—2.30 PM

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OBJECTIVES

• CORNEA :-- Development & anomalies.

• LENS:-- Development and anomalies.

• RETINA:- Development and anomalies.

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OPTIC VESICLE

• The eye begins developing in the early embryo at 28 days after fertilization (equivalent to six weeks of pregnancy) as an out-pouching of both sides of the brain called the optic vesicle.

• The optic vesicle grows and makes contact with the surface of the embryonic face, this contact produces a surface thickening called a placode that subsequently forms the lens of the eye.

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Optic cup growing from forebrain vesicle

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OPTIC CUP

• The out-pouching then changes shape to form the optic cup ultimately forming a hollow sphere with a space containing the lens at the front and a gap along the bottom called the optic fissure.

• The optic fissure must then fuse to form a normal eye, failure of this step will cause coloboma.

• Failure of any of the processes involved in early eye development may cause anophthalmia (absence of eye) and/or microphthalmia ( small eye).

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Coloboma

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Structures developing from diencephalon

• Thalamus, epithalamus, hypothalamus, sub thalamus, neurohypophysis, pineal gland, retina, optic nerve, mamillary bodies.

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Optic vesicle grows from the forebrain, and induces changes in

the surface ectoderm

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Formation of lens placodefrom the surface ectoderm

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Lens placode• Once the formation of

the lens placode (1) has begun, the expanding optic vesicle begins to invaginate to form a cup-shaped structure, and also to fold along its centerline, enclosing a small amount of angiogenic mesenchyme as it does so.

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Hyaloid artery

• This mesenchyme forms the hyaloid artery and vein, which supply the forming lens; and later, in the fully formed stage will become the central artery and vein of the retina.

• Hyaloid canal.

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The hyaloid artery after wards remain as central retinal artery

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Formation of retina

• The cup invaginates and folds, it is forming two distinct layers. The inner layer of the optic cup will eventually form the retinal tunic, including its light-sensitive elements.

• The outer layer of the optic cup will form the pigment epithelium layer, which lies outside the sensitive portion. The embryonic intraretinal space is obliterated when these two layers fuse.

• The uveal and corneoscleral tunics eventually will differentiate from the surrounding mesoderm.

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The two layers of optic cup forms the sensitive layer and pigmented

layer.

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The iris is the only muscle that develops from the ectoderm

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Cornea

It is an ectodermal derivative, develops from the surface ectoderm.

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Cornea development

• The cornea, although it fuses with the sclera, is derived solely from ectoderm, and it is therefore avascular in its final form.

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Lens vesicle, surrounding mesenchyme/ optic cup

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Applied anatomy

• 1. Congenital cataract.

• 2. Subluxation of lens.

• 3. Retinal detachment.

• 4.Retinoblastoma.

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Congenital cataract/one of the cause is rubella infection during

pregnancy

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Subluxation of lens

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Retinal detachment

• It is due to separation between the two layers of optic cup.

• It is a congenital disorder.

• It is a developmental disorder.

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Retinoblastoma

• Retinoblastoma is a cancer of the eye in children. It originates from the retina, the light sensitive layer, in eye.

• It is the commonest eye tumor in childhood.

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Review of development of eye

• The surface ectoderm gives rise to the lens, the lacrimal gland, the epithelium of the cornea, conjunctiva, and adnexal glands, and the epidermis of the eyelids.

• The neural ectoderm gives rise to the optic vesicle and optic cup and is thus responsible for the formation of the retina and retinal pigment epithelium, the pigmented and nonpigmented layers of ciliary epithelium, the posterior epithelium, the dilator and sphincter muscles of the iris, and the optic nerve.

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Development of extra ocular muscles

• The mesoderm is now thought to contribute only to the extra ocular muscles and the orbital and ocular vascular endothelium.

• The intraocular muscles, sphincter pupillae and dilator pupillae develops from neuroectoderm.

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See you in exams