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Flashcards in Optic nerve head Deck (39)
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1

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

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

2

What consists of the surface nerve fiber layer

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

3

What is the prelaminar region

Nerve axons and astrocytes with significant increase in astroglial tissue

4

What is lamina cribrosa

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

5

What is the retrolaminar region

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

6

Vasculature of the optic nerve head

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

7

Blood vessel to optic nerve

Through the central retinal artery

8

Blood vessel supply to surface nerve fiber layer

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

9

Blood vessel supply to prelaminar and laminar regions

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

10

Blood vessel supply to retrolaminar region

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

11

Where are the capillaries derived from

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

12

Where does venous drainage occur

Through the central retinal vein

13

What does astroglial support do

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

14

What do the thin astrocytes do

Accompany the axons in the nerve fiber layer

15

What do the thick astrocytes do

Direct axons from prelaminar to laminar region

16

Where does glaucoma pathogenesis take place

lamina cribrosa

17

Where is the porous region of the sclera

lamina cribrosa

18

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

TRUE

19

What determines a healthy analysis of pores in lamina cribrosa

Round in eyes with physiologic cupping

20

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

Superiorly and inferiorly: Larger
Nasally and temporally: smaller

21

Where do the arcuate fibers occupy

Superior and inferior temporal regions

22

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

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

23

How many axons are there

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

24

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

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

25

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

True

26

what is the rate of the loss of axons

4,000 to 12,000 a year

27

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

False

28

What do retinal ganglion cells depend upon

neuronal growth factor, neurotrophins

29

When is nitric oxide beneficial. when is it not

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

30

What is the mechanical theory of incluencing IOP

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