Self Study 4 - Embryology of the eye

Question 1

How does the neural tube form:

Answer 1

Ectoderm thickens to form neural plate
Neural crests from from ectoderm
Crests meet forming a hollow tube underneath called the neural tube

Question 2

How do the eyes begin to form from the neural tube?

Answer 2

The Diencephalic vesicle of the neural tube give off lateral projections called the optic vesicles.

The optic vesicles reach the surface ectoderm which thickens (a placode - thicker embryological area) to form the optic placodes.

Question 3

How are the optic cups formed?

Answer 3

The Optic placode invaginates, in turn pushing the optic vesicle to invaginate (forming a two layered optic cup around the placode)

Question 4

What happens to the optic placode?

Answer 4

After it invaginates it seperates from the surface ectoderm becoming the lens vesicle which sits in the optic cup

Question 5

How do developing blood vessels reach the optic cup?

Answer 5

Through a fissure in its inferior wall called the choroid fissure.

Question 6

What forms the choroid and sclera?

Answer 6

Mesenchyme around the optic cup

Question 7

What happens if the choroid fissure fails to close before birth?

Answer 7

Part of your eye (e.g. Iris, optic disc or retina) has a key-hole shaped opening called a coloboma

Question 8

What do the two layers of the optic cup form?

Answer 8

Inner layer forms the inner 9 retinal layers
Outer layer forms the 10th retinal layer

This leaves a potential space between the two that can fill with fluid if perforated and cause retinal detachment

Question 9

What structures ultimately from surface ectoderm?

Answer 9

• Eyelids
• Conjunctiva
• Corneal Epithelium

Question 10

What structures ultimately form from mesenchyme?

Answer 10

Choroid
Stroma of cornea
Sclera
Extraocular muscles