D evelopment of eye
- 1. DEVELOPMENT OF EYE DR NEETA CHHABRA
- 2. Development of Eye • Begins at 3rd week and continues through the tenth week • Cells from both ectodermal & mesodermal tissues contribute to the formation of eye • Ectoderm : Surface ectoderm Neuro ectoderm • Mesoderm : Extracellular mesenchyme which consists of both, the neural crest cells and mesoderm • Endoderm does not take part in formation of Eye
- 3. Formation of Optic vesicle • At 22nd day of IUL, neural plate destined to form prosencephalon shows thickened area on each side that becomes depressed to form Optic sulcus • Optic sulcus bulges outwards to form Optic vesicle • Proximal part of optic vesicle becomes constricted and elongated to from Optic stalk
- 4. Formation of Lens vesicle • As the optic vesicle comes in contact with surface ectoderm, it thickens : Lens placode • Lens placode depresses to form Lens pit & later, Lens vesicle • Lens vesicle loses contact with surface ectoderm by 33rd day
- 5. Formation of Optic cup • Optic vesicle is converted into a double layered structure : Optic cup • This is due to differential growth of walls of the optic vesicle • The optic cup grows over the upper & lateral side of lens & not on the inferior aspect leading to a gap : Choroidal fissure or fetal fissure
- 6. Changes in Associated Mesoderm • Developing neural tube is surrounded by mesoderm, that differentiates to form: Superficial fibrous layer : Dura mater Deep vascular layer : Pia-arachnoid • This mesoderm covers optic vesicle also
- 7. Mesenchyme • A part of this mesoderm along with blood vessels is carried into the optic cup through choroidal fissure: hyaloid vessels • Distal part of vessels degenerate, proximal part form central artery & vein of retina Changes in Associated Mesoderm
- 8. • Lens vesicle: Lined by a single layer of cuboidal cells • Cells of ant wall remain cuboidal: Epithelium • Cells of post wall elongate, become columnar & obliterate the cavity of the lens vesicle • They lose their nuclei & form primary lens fibers • New lens fibers are formed from equatorial cells of anterior part which later become hard & form secondary lens fibers & lens grows Development of Lens
- 9. Development of Retina • Develops from optic cup : Neuroectoderm • Optic cup has 2 parts: Anterior & Posterior • Anterior part : Thin, forms ciliary & iridial parts of retina • Posterior part : Thick, forms various layers of retina. It has 2 walls • Outer wall: Pigmented layer of retina • Inner wall : Nervous layer of retina
- 10. Retina & Optic Nerve • Inner wall: Differentiates into 3 layers • Matrix layer : Forms rods and cones • Mantle layer: Forms bipolar cells, ganglionic cells, other neurons & supporting tissue • Marginal layer: Axons of ganglion cells converge towards optic stalk & forms Optic Nerve
- 11. • During embryonic & early foetal life, pigment & neural layers of retina are separated by intra retinal space which represents the original cavity of the optic cup • Before birth this space is obliterated due to proliferation of cells of inner layer • Thus, rod & cone cells come in contact with pigment layer of retina Development of Retina
- 12. Sclera and Choroid • During 6th or 7th week of IUL mesenchyme surrounding external surface of optic cup condenses into two layers: Outer fibrous layer: Sclera Inner vascular layer : Choroid • Sclera is continuous anteriorly with substantia propria of cornea & posteriorly with dura mater • Choroid is continuous anteriorly with ciliary body & iris & posteriorly with pia arachnoid
- 13. Ciliary Body • Derived from forward prolongation of mesoderm forming the choroid • Epithelium : Two layers of Optic cup Outer pigmented layer : Pigmented layer of choroid Inner non pigmented layer : Neural layer of choroid • Stroma,ciliary muscle & blood vessels : Vascular mesoderm
- 14. Iris • Derived from forward prolongation of mesoderm forming the choroid • Epithelium : Two layers of Optic cup Outer pigmented layer : Pigmented layer of optic cup Inner non pigmented layer : Neural layer of optic cup • Stroma & blood vessels : Vascular mesoderm • Muscles : Neuroectodermal cells of optic cup
- 15. Cornea Cornea consists of 5 layers • Outer Stratified squamous epithelium: Surface ectoderm • Bowman’s membrane & Lamina propria: Mesoderm • Descemet’s membrane & inner corneal epithelium: Neural crest cells
- 16. Anterior & Posterior Chambers of Eye • Anterior chamber : Splitting of Mesoderm between iris & cornea • Posterior chamber : Splitting of Mesoderm between iris & lens • Filled with aqueous humour secreted by ciliary processes of ciliary body • Communicate with each other after disappearance of pupillary membrane • Aqueous humour is drained by canal of Schlemm
- 17. Vitreous • Vitreous develops as follows: • Primary vitreous develops from mesoderm It is vascular having hyaloid vessels • Secondary vitreous is secreted by neuroectoderm of optic cup. It is avascular • Secondary vitreous replaces the primary vitreous
- 18. Eyelids • Develop from reduplication of surface ectoderm • Muscles & tarsal plates : Mesoderm • Folds grow & fuse with each other • Space enclosed within folds : Conjunctival sac • Conjunctiva : Ectodermal origin • Eyelids remain fused till 7 month of IUL
- 19. Lacrimal Apparatus • Lacrimal Gland: Develops from 15 to 20 buds from the superolateral angle of conjunctival sac • Lacrimal sac & Nasolacrimal duct: Develop from ectoderm of Nasolacrimal furrow • Lacrimal canaliculi develop from canalization of ectodermal buds that grow from medial ends of each eyelid into lacrimal sac
- 20. Extraocular Muscles Mesenchymal condensation (Pre occipital myotomes)
- 21. Anomalies of Eye 1. Anophthalmia 2. Microphthalmia 3. Synophthalmia 4. Cyclopia 5. Proboscis
- 22. Anomalies of Lid & Lens 1. Entropion 2. Ectropion 3. Coloboma of eyelid 4. Coloboma of iris 5. Epicanthus 6. Aphakia 7. Congenital Cataract
- 23. Summary Part Source Sclera Mesoderm Choroid Mesoderm Retina Neuroectoderm (Optic cup) Lens Surface ectoderm Vitreous Primary (Mesoderm) Secondary (Neuroectoderm) Ciliary body Mesoderm Epithelium : Optic cup (Neuroectoderm) Ciliary muscle Mesoderm Iris Mesoderm Epithelium : Optic cup (Neuroectoderm) Sphincter & dilator pupillae Neuroectoderm ( Optic cup) Cornea Surface epithelium (Ectoderm) Rest of the layers (Mesoderm) Conjunctiva Surface ectoderm Optic nerve Neuroectoderm Coverings (Mesoderm)
- 24. THANKS