Development of eyeTo MBBS 2nd year

Dr. Laxman Khanal

Assistant professor, department of anatomy

BPKIHS, Dharan

02-04-2017

Eye development : start at Day 22.

Before NT closure- Day 25 to Day 28

Diencephalon of forebrain

PAX 6Key regulatory gene for eye development.

Optic vesicleOptic groove

Lens placode Optic stalk Optic cup

1. Fibrous covering2. Vascular covering (#ICC)3. Nervous covering

Limbus Equator

• Key steps - Formation of optic vesicle and optic stalk.

• Optic vesicle/ stalk – neuro-ectodermal in origin.

• Lumen of the optic vesicle is connected with the 3rd ventricle through thelumen of optic stalk.

• As the optic vesicle comes in contact with the surface ectoderm, itinduces it to thicken and forms lens placode (primordium of lens), so lensis ectodermal (surface ectoderm) in origin.

• As the lens vesicle is being formed, optic vesicle invaginates to formdouble-layered optic cup.

Choroidal fissure• Vascular mesoderm invade the fissure.• This mesoderm later form hyaloid vessels &

vitrous humor.• Only the proximal part of these vessels persists

as a central artery/vein of retina

Up to now…..• Optic vesicle• Optic cup• Optic stalk• lens placode• Choroidal fissure

Development of Retina- two layers of optic cupDevelopment of optic nerve- optic stalk (axons of ganglion cells)

Retinal detachment:

Separation of pigment epithelium from the neural layer.

Ora serrata

• Ora serrata is the junction betweenphotosensitive and non-photosensitiveretina.

• Lies between limbus and equator of eyeball.

Coloboma• Failure to close choroidal fissure• Key hole appearance in iris• Follow AD inheritance

Retinal detachment • Medical emergency• Occurs between 2 layers of retina

Development of optic nerve

• Second cranial nerve• Optic nerve encloses retinal vessels• Formed by axons of ganglionic cells• Covered by meningeal layers• Myelinated by Oligodendrocytes

@ 7th week

Development of-• Iris• Ciliary body

Development of IrisEpithelium: both layers of retina (ant part)Stroma: mesenchymeMuscles: outer layer of retina

Development of ciliary bodyEpithelium: both layers of retina (ant part)Stroma: mesenchymeMuscles: mesenchyme

Aqueous humor

Derivatives of optic cup • Retina• Dilator pupillae• Sphincter pupillae• Epithelium of the iris• Epithelium of ciliary body

Derivatives of optic stalk

Optic nerve

MesodermPosteriorlydivide into two layersAnteriorlyVacuolization occurs

Surface Ectoderm Double folding occurs

Development of-• Sclera• Choroid• Cornea• Conjunctiva• Eyelids

Double folding of surfaceectoderm give rise to theconjunctiva and eye lids.

Surface Ectoderm • Outer epithelium of cornea• Conjunctiva• Lining of eye lids• Tarsal gland• Eye lashes

Persistent iridopupillary membrane Congenital cataractTORCH infection

Aniridia

Synophthalmiaor

CyclopiaLoss of midline structure• Alcohol• Maternal DM• Mutation of SHH (sonic hedgehog)• Abnormal cholesterol metabolism

Conclusion

• The eyes begin to develop as a pair of outpocketings on each side ofthe forebrain at day 22.

• The optic vesicles contact the surface ectoderm and induce lens formation.

• Through a groove (the choroid Fissure), the hyaloid artery (later thecentral artery of the retina) enters the eye

• PAX6, the master gene for eye development.

• Cornea develops from both ectoderm and mesoderm.