Eye Development

Question 1

What part of the developing brain do structures of the eyes come from? What else comes from this

Answer 1

Prosencephalon

Things with thalmus in name

Question 2

What does the optic vesicle become during development? When does this happen? What is it attached to?

Answer 2

Optic cup

Week 4

optic stalk

Question 3

What’s contained in the optic fissure?

Answer 3

vasculature

Question 4

What is the optic sulcus?

Answer 4

Groove only seen from inside of developing eye

Question 5

What does the retina arise from? What are its 2 layers?

Answer 5

Neuroectoderm

Neural retina (inner) 
Pigmented retina (outer)

Question 6

What do the structures of the iris arise from? Where do you find them during development?

Answer 6

Epithelium= neuroectoderm
Stroma= mesenchyme (mesoderm AND NCC)
SMC aka pupillae muscles= neurectoderm (only muscles that come from neurectoderm)

Tip of optic cup

Question 7

What do the structures of the ciliary body arise from? Where do you find them during development?

Answer 7

Epithelium= neuroectoderm
SMC= ciliary muscles, from mesoderm and NCC aka mesenchyme

Question 8

What is the critical period for eye development?

Answer 8

Week 4-8

Can have defects up to birth though

Question 9

What causes retinal detachment?

Answer 9

The inner and outer layers of the retinal cup fail to fuse

• common in people with marfan’s or downs
• can also be caused by trauma to eye

Question 10

What is aniridia? Embryologically how is this caused? What gene mutation is it associated with?

Answer 10

Lack of iris tissue or complete absence of iris

Arrest of development at rim of optic cup during 8th week

Pax6 gene

Question 11

How does the lens develop? What layer does it come from?

Answer 11

Induced by optic cup

Lens placode grows out touching surface ectoderm resulting in new genetic signaling and thickening of surface ectoderm –> invaginate and become lens pit –> round up and become lens vesicle

Surface ectoderm

Question 12

What fibers during development are important in ensuring the lens is clear?

Answer 12

anterior lens epithelium
primary lens fibers
secondary lens fibers

Question 13

Where do the parts of the cornea arise from?

Answer 13

Epithelium= surface ectoderm

Stroma= mesenchyme (includes NCC)

Question 14

What can cause congenital cataracts?

Answer 14

Genetics
Rubella virus during weeks 4-7
Radiation
Enzyme deficiency –> congenital glactosemia, appears 2-3 weeks after birth when galactose from milk accumulates

Lens is opaque and grayish white, ONLY LENS OPAQUE (different than glaucoma)

Question 15

What does the sclera develop from? What are its parts?

Answer 15

Mesenchyme/NCC

Outer layer continuous with dura matter
Fibrous
stroma of cornea

Question 16

What does the choroid develop from? What are its parts?

Answer 16

Heavily NCC

Inner layer continous of pia and arachnoid matter
Vascularized

Question 17

What is the pupillary membrane? When does it normally disintegrate?

Answer 17

extension of the sclera, covers the lens as it is developing

during months 6-8

Question 18

What is the pathway of aqueous humor?

Answer 18

Secreted by ciliary epithelium (neuroectoderm) –> posterior chamber –> pupil –> ant chamber –> reabsorbed by scleral venous sinus (mesenchyme)

Question 19

What is virteous humor made by?

Answer 19

The choroid

Gel like substance in eye when cut open

Question 20

What does congenital glaucoma result from embryologically? Pathologically?

Answer 20

Abnormal development of drainage mechanism of aqueous humor aka sclera venous sinus –> elevated intraocular pressure

Genetics, CYP1B1 mutation
Rubella

Question 21

Where do the extra-cular muscles arise from? are they arch structures?

Answer 21

Prechordal plate mesenchyme

NOOO

Question 22

What does the hyaloid artery arise from? What does it supply? What does it differentiate into? What does it supply?

Answer 22

Mesenchyme (branch of the ophthalmic a.)

Inner layer of optic cup, lens vesicle, mesenchyme in optic cup

Distal “webbing” disintegrates and becomes central artery surrounded by optic stalk supplying only the retina

Question 23

What does the choroidal vessel develop from? When does this happen?

Answer 23

Mesenchyme, specifically anterior and posterior ciliary arteries

15th week

Question 24

What happens if there is persistence of the hyaloid a. distally?

Answer 24

See floating worm in eye
Normally associated with cases of microphthalmic aka small eye condition
Little/no defects

Question 25

What does the optic nerve come from? What are its layers?

Answer 25

Neuroectoderm
Pigments= rods and cones, ganglion cells
Fibrous layer= axons forming optic nerve

Question 26

How does the optic nerve form?

Answer 26

Inner layer of optic stalk with axons and ganglion

• axons grow through the inner part of the stalk forming nerve and cavity obliterated
• hyaloid a incorporated into substance of optic n.

finally in 7th week artery covered by all 3 meningeal layers

Question 27

What is papilledema?

Answer 27

Increased intracranial pressure –> slow venous return from retina –> fluid accumulation of the optic disc –> edema because vessels covered by meninges and lie in extension of subarachnoid space

OPTIC DISC BULGE

Question 28

What is colobma? Embryologically how does this arise?

Answer 28

Key hole pupil –> in bright light cant constrict at that point so can cause damage to retina

Failure of optic fissure to close
- can be caused by environmental factors or autosomal dominant mutation

Question 29

What defects can the rubella virus have on the eye?

Answer 29

Cataracts
Microphthalmos
Glaucoma
Pigmented Retinopathy

Question 30

What defects can taxoplasam gondi (intracellular parasite fro uncooked meat, soil, infected animals)?

Answer 30

Micropthalamia

Question 31

What defects can venezuelan equine encephalitis virus have on the eye?

Answer 31

micropthalmia

Question 32

What defects can varicella (chicken pox) have on the eye?

Answer 32

cataracts
microphthalmia
optic atrophy