Optic nerve head

Question 1

What are the four parts that the optic nerve head is divided into

Answer 1

1. Surface nerve fiber layer
2. Prelaminar region
3. Lamina cribrosa region
4. Retrolaminar region

Question 2

What consists of the surface nerve fiber layer

Answer 2

innermost portion, predominantly nerve fiber, axonal bundle acquire more ineraxonal glial tissue as this structure is followed posteriorly

Question 3

What is the prelaminar region

Answer 3

Nerve axons and astrocytes with significant increase in astroglial tissue

Question 4

What is lamina cribrosa

Answer 4

Continuation of the sclera. Has fenestrated scleral tissue. Astrocytes sep. the sheets and line the holes. Bundle of axons leave through these holes

Question 5

What is the retrolaminar region

Answer 5

Decrease in astrocytes, myelin is acquired. Axonal bundles surrounded by connective tissue. Posterior limit is not clear but about 3 to 4 mm

Question 6

Vasculature of the optic nerve head

Answer 6

arterially: posterior ciliary artery, except for nerve fiber layer which is supplied by retinal circulation

Question 7

Blood vessel to optic nerve

Answer 7

Through the central retinal artery

Question 8

Blood vessel supply to surface nerve fiber layer

Answer 8

main supply arterioral branches of central retinal artery. anastomize with the vessels of the prelaminar region

Question 9

Blood vessel supply to prelaminar and laminar regions

Answer 9

Primary supply: short posterior ciliary arteries. Forms circle of zinn-haller. also supply peripapillary choroid

Question 10

Blood vessel supply to retrolaminar region

Answer 10

medial and lateral perioptic nerve short posterior ciliary artery
Form an elliptical arterial circle around the optic nerve (also called circle of zinn haller)

Question 11

Where are the capillaries derived from

Answer 11

Both retinal and ciliary circulation. Resemble retinal capillaries. Don’t leak fluorescein and may represent nerve blood barrier. Decrease in number posterior to lamina

Question 12

Where does venous drainage occur

Answer 12

Through the central retinal vein

Question 13

What does astroglial support do

Answer 13

Provides continuos layer between nerve fiber and blood vessels of optic nerve head.

Question 14

What do the thin astrocytes do

Answer 14

Accompany the axons in the nerve fiber layer

Question 15

What do the thick astrocytes do

Answer 15

Direct axons from prelaminar to laminar region

Question 16

Where does glaucoma pathogenesis take place

Answer 16

lamina cribrosa

Question 17

Where is the porous region of the sclera

Answer 17

lamina cribrosa

Question 18

T/F Hyaluronate decreases with age and with increase in IOP

Answer 18

TRUE

Question 19

What determines a healthy analysis of pores in lamina cribrosa

Answer 19

Round in eyes with physiologic cupping

Question 20

How are the lamina pores superiorly what about inferiorly. what about nasally and temporally

Answer 20

Superiorly and inferiorly: Larger

Nasally and temporally: smaller

Question 21

Where do the arcuate fibers occupy

Answer 21

Superior and inferior temporal regions

Question 22

Which fibers spread approx 1/3 of the distal optic nerve primarily inferior temporal

Answer 22

papillomacular fibers. It also intermingles with extramacular fibers (may explain retention of central vison)

Question 23

How many axons are there

Answer 23

70,000 to 1.2 million. Inc with inc in area

Question 24

What is the influence of age in regards to the optic nerve head

Answer 24

The size of the onh is 95% before age 1.

Question 25

T/F The CT of lamina cribrosa is incompletely developed in young children

Answer 25

True

Question 26

what is the rate of the loss of axons

Answer 26

4,000 to 12,000 a year

Question 27

T/F There is a selective loss of fibers with age

Answer 27

False

Question 28

What do retinal ganglion cells depend upon

Answer 28

neuronal growth factor, neurotrophins

Question 29

When is nitric oxide beneficial. when is it not

Answer 29

Beneficial at certain concentration as a vasodilater
Neurotoxic in higher concentration
Inhibits mitochondrial function and disrupts DNA.

Question 30

What is the mechanical theory of incluencing IOP

Answer 30

PHysical alterations, misalignment of fenestrae, backbowing of lamina cribrosa may lead to obstruction.

Question 31

What is the vascular theory

Answer 31

Ischemia plays a role in the obstruction of axoplasmic flow in response to elevated IOP

Question 32

What is perfusion pressure

Answer 32

Difference between arterial and venous pressure

Question 33

What is the mean ocular perfusion pressure

Answer 33

mean BP - IOP

Question 34

Can retina auto regulate?

Answer 34

YES

Question 35

What are the two types of autoregulatory mechanisms

Answer 35

metabolic and myogenic

Question 36

What is secreted in metabolic autoregulatory mechanism

Answer 36

vasodilators - nitric oxide

vasoconstrictors - endothelin 1

Question 37

When does myogenic mechanism operate

Answer 37

when blood flow is above normal

Question 38

What is the evidence in favor of vascular theory

Answer 38

Delayed filling of superficial vessels of optic nerve in glaucoma
Association of NTG with migraines
Excessive peripheral constriction of vessels to cold - Raynauds phenomenon
Nocturnal blood flow diffrent in glaucoma patients
Greater plasma concentration of endothelin 1

Question 39

Is the larger disc area postively correlated with what

Answer 39

neural rim