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The eyes begin to The eyes begin to develop from a develop from a population of cells in the population of cells in the anterior neural plate at anterior neural plate at the end of the 4the end of the 4thth week week of development.of development.

These cells make up the These cells make up the eye fields.eye fields.

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• Optic grooves (sulci) form as Optic grooves (sulci) form as some of the cells in the eye some of the cells in the eye fields invaginates.fields invaginates.

• The optic grooves form the optic The optic grooves form the optic stalks and the optic vesicles.stalks and the optic vesicles.

• Contact between the neural Contact between the neural ectoderm of the optic vesicle and ectoderm of the optic vesicle and the surface ectoderm results in the surface ectoderm results in induction of the lens placode.induction of the lens placode.

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• The invaginating The invaginating lens placode forms lens placode forms the lens vesicle that the lens vesicle that pinches off the pinches off the surface ectoderm. surface ectoderm. Invagination of the Invagination of the optic vesicle forms optic vesicle forms the bilayered optic the bilayered optic cup that remains cup that remains connected to the connected to the forebrain via the forebrain via the optic stalk.optic stalk.

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• Contact between Contact between the surface the surface ectoderm and the ectoderm and the budding optic budding optic vesicle induces vesicle induces the differentiation the differentiation of a population of of a population of cells that will form cells that will form the lens placode.the lens placode.

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• The lens placode invaginates, The lens placode invaginates, forming the lens vesicle. forming the lens vesicle. Concurrently, the optic vesicle Concurrently, the optic vesicle becomes the optic cup.becomes the optic cup.

• The lens vesicle eventually The lens vesicle eventually becomes the lens and the two becomes the lens and the two layers of the optic cup become the layers of the optic cup become the neural and pigmented layers of the neural and pigmented layers of the retina.retina.

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• The optic vesicle The optic vesicle and the optic and the optic stalk stalk invaginates, invaginates, forming the forming the choroid fissure choroid fissure inferiorly.inferiorly.

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The hyaloid artery courses through the choroid The hyaloid artery courses through the choroid fissure.fissure.  

  

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•   The hyaloid vasculature The hyaloid vasculature surrounds the back of the lens. surrounds the back of the lens. Following separation of the lens Following separation of the lens from the surface, the posterior from the surface, the posterior lens fibers elongate to obliterate lens fibers elongate to obliterate the lens cavity and the cornea the lens cavity and the cornea begins to differentiate.begins to differentiate.

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• The anterior The anterior chamber of the chamber of the eye forms as a eye forms as a space develops space develops between the lens between the lens and its closely and its closely associated associated iridopupillary iridopupillary membrane and membrane and the cornea.the cornea.

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• The cornea consists of an outer The cornea consists of an outer epithelial layer derived from epithelial layer derived from surface ectoderm and inner layers surface ectoderm and inner layers derived from neural crest cells.derived from neural crest cells.

• As the retina develops, the As the retina develops, the pigmented layer becomes pigmented layer becomes relatively thinner while the neural relatively thinner while the neural portion thickens.portion thickens.

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• As the neural As the neural portion portion develops, it develops, it differentiates differentiates into distinct cell into distinct cell layers.layers.

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•   The iris forms from the outer The iris forms from the outer rim of the optic cup.rim of the optic cup.

• At the rim of the optic cup, the At the rim of the optic cup, the inner and outer layers become inner and outer layers become closely associated.closely associated.

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• Folding of these Folding of these layers results in layers results in formation of the formation of the ciliary processes.ciliary processes.

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• By the end of the embryonic By the end of the embryonic period, eyelids begin to form.period, eyelids begin to form.

•   The eyelids fuse at the The eyelids fuse at the beginning of the second beginning of the second trimester and reopen at the trimester and reopen at the beginning of the third trimester.beginning of the third trimester.

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CONGENITAL CONGENITAL MALFORMATIONSMALFORMATIONS

• Coloboma iridis - failure of closure of Coloboma iridis - failure of closure of choroid fissure due to which cleft choroid fissure due to which cleft persists.persists.

• Congenital cataract - lens becomes Congenital cataract - lens becomes opaque during intrauterine life.opaque during intrauterine life.

• Microophthalmia – overall size of the Microophthalmia – overall size of the eye is too small.eye is too small.

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Embryonic eye, with lens Embryonic eye, with lens vesiclevesicle

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Embryo, brain with optic and Embryo, brain with optic and lens vesicleslens vesicles