Eye Development

Question 1

What 3 embryonic sources contribute to the development of the eye?

Answer 1

Neuroectoderm, surface ectoderm, and mesoderm/neural crest

Question 2

What is the origin of the eye?

Answer 2

Prosencephalon

Question 3

When does development of the optic cup begin?

Answer 3

4 weeks

Question 4

What are the parts of the developing eye?

Answer 4

Optic groove (sulcus), optic vesicle, optic stalk, optic cup, and optic fissure

Question 5

What parts of the eye come from neuroectoderm?

Answer 5

Retina, iris, and ciliary body

Question 6

What are the parts of the retina?

Answer 6

Neural retina and pigmented retina

Question 7

What makes up the iris?

Answer 7

Epithelium, stroma, and smooth muscle cells

Question 8

What makes up the ciliary body?

Answer 8

Epithelium, smooth muscle cells (from mesoderm), and ciliary muscle

Question 9

What occurs during detachment of the retina?

Answer 9

The pigmented and neural retinas become separated

Question 10

What is aniridia? What causes this?

Answer 10

Lack of iris tissue or complete absence of the iris; may be associated with glaucoma, cataracts, other eye abnormalities, or a Pax6 gene mutation

Question 11

What parts of the eye come from surface ectoderm?

Answer 11

Lens placode, lens pit, lens vesicle, anterior lens epithelium, primary/secondary lens fibers, and epithelium of cornea

Question 12

What is induction in terms of the lens?

Answer 12

Lens development is induced by the optic cup through cell-cell interactions

Question 13

What is congenital cataracts? What causes this?

Answer 13

Lens is opaque and frequently appears grayish-white; caused by genetics, rubella virus, radiation, or an enzyme deficiency

Question 14

When is the lens most vulnerable to the rubella virus, leading to cataracts?

Answer 14

Weeks 4-7

Question 15

What is congenital galactosemia?

Answer 15

Occurs when galactose from milk accumulates in blood and tissues; appears 2-3 weeks after birth; form of cataracts

Question 16

What parts of the eye come from mesenchyme/neural crest cells?

Answer 16

Sclera, choroid, pupillary membrane, and ciliary body

Question 17

What is the sclera?

Answer 17

It is the outer layer; it is fibrous and forms stoma of cornea

Question 18

What is the choroid?

Answer 18

It is the inner layer (pia and arachnoid); it is vascular and this is the neural crest cell contribution

Question 19

What is the papillary membrane?

Answer 19

It is a transient structure and forms part of the sclera

Question 20

What occurs in the anterior chamber of the eye?

Answer 20

Aqueous humor is resorbed by scleral venous sinus

Question 21

What occurs in the posterior chamber of the eye?

Answer 21

Aqueous humor is secreted by ciliary epithelium

Question 22

Where does vitreous humor come from? Who primarily makes aqueous humor?

Answer 22

Vitreous: primarily from choroid

Aqueous: made by ciliary body

Question 23

What is congenital glaucoma? What causes it?

Answer 23

Elevated intraocular pressure resulting from abnormal development of the drainage mechanism of aqueous humor (scleral venous sinus); caused by mutations in CYP1B1 gene in 85% of cases; can be caused by rubella infection

Question 24

Where do extra-ocular eye muscles come from?

Answer 24

Prechordal mesenchyme

Question 25

Where does the eye get its blood supply? What does this artery supply? What does this artery become?

Answer 25

Hyaloid artery (branch of opthalmic); supplies inner layer of optic cup, lens vesicle, and mesenchyme in optic cup; becomes central artery

Question 26

When do the choroid vessels develop?

Answer 26

During the 15th week

Question 27

What is persistence of the hyaloid artery?

Answer 27

Occurs when distal part of hyaloid artery persists when it should degenerate; in most cases the eye is microphthalmic

Question 28

What makes up the optic nerve?

Answer 28

2 layers of neuroblasts (rods and cones and ganglion cells) and a fibrous layer (axons forming the optic nerve)

Question 29

Where do the fibers of the optic nerve grow? What happens during this process?

Answer 29

Fibers grow through inner part of the optic stalk; the cavity becomes obliterated and the hyaloid artery becomes incorporated

Question 30

What is papilledema? Why does edema occur with this?

Answer 30

Occurs when increased intracranial pressure slows venous return from retina, causing fluid accumulation in the optic disc; edema occurs because the retinal vessels are covered by the meninges and lie in the extension of the subarachnoid space

Question 31

What is coloboma? What causes it?

Answer 31

Results from failure of optic fissure to close, leaving a gap in eye structures

Question 32

What eye defects can a rubella virus cause?

Answer 32

Cataracts, microphthalmos, glaucoma, pigmented retinopathy

Question 33

What eye defects can toxoplasma gondii cause?

Answer 33

Microphthalmia

Question 34

What eye defects can venezuelan equine encephalitis virus cause?

Answer 34

Microphthalmia

Question 35

What eye defects can varicella virus cause?

Answer 35

Cataracts, microphthalmia, and optic atrophy