Optic Nerve in Glaucoma

Question 1

who is more likely to have a larger disc?

Based on gender and race

Answer 1

AA > caucasian
Males > females

Should not change w age

Question 2

ONH blood supply characteristics and main blood supply

Answer 2

Non fenestrated
Autoregulated (unlike in choroid)
Main supply from posterior ciliary arteries

Question 3

Autoregulation

Answer 3

Intrinsic ability of vascular beds to maintain a constant level of blood flow regardless of changes in perfusion pressure and metabolic demands.

Question 4

How does autoreg change with IOP increases??

Answer 4

NO is released and vessels dilate to increase blood flow to tissues. If autoreg does not work, it can lead to ONH damage

Question 5

Autoreg factors

Answer 5

Endothelin 1 constricts

NO dilates

Question 6

Axoplasmic flow

Answer 6

Energy dependent process of transmitting cellular material through an axon.

Growth factors (brain derived neurotrophic factor) travels from LGN to ganglion cells. Without, it will lead to glaucoma damage.

Question 7

2 things that disrupt axoplasmic flow

Answer 7

Pinching of nerve (mechanical) or decreased blood flow to nerve.

Question 8

Perfusion pressure

Answer 8

Blood flow pressure to the ONH. Balance of BP and IOP.

Question 9

PP is proportional to ____ and inversely proportional to ___

Answer 9

Blood pressure. Increase BP will increase blood flow to the nerve.

Inverse to IOP bc IOP blocks blood flow to the nerve.

Question 10

How to calculate PP?
Less than __mmHg may be risk for glaucoma bc perfusion pressure is too low (aka ONH is not getting enough blood flow. autoreg will kick on but can only dilate so far before dysregulation occurs).

Answer 10

Diastolic - IOP

Question 11

What happens when autoregulatio breaks down

Answer 11

Perfusion pressure increases and causes vessel wall damage to pericytes and may cause atherosclerosis

Question 12

Ganglion cell types

Answer 12

P: More numerous, at fovea. Small receptive field, sustained stimuli.

M: Even distribution across retina. Responds to transient and low spatial frequency changes in the periphery. Preferentially damaged in glaucoma. VF testing done to evaluate the system.

Question 13

ON changes- violating ISNT rule and vertical elongation

Answer 13

Poles are at greater risk for damage due to axons entering and the NRR not being able to support them.

Question 14

ON changes- NRR notching

Answer 14

FOCAL damage or loss within the NRR on the inner edge of the cup. Looks like NRR has been eaten away. Associated with RNFL defect

Question 15

NRR notching vs pit

Answer 15

notching is focal damage within the NRR on the inner edge of the cup.

Pit is depending of the area within the center cup. Grey, oval appearance.

Question 16

ON changes= concentric enlargement of cup

3 examples

Answer 16

Deepening. Includes bean potting, bayonetting, and vessel baring

Question 17

Bean potting and bayonetting appearance due to concentric enlargement of cup

Answer 17

Bean potting: Describes what is happening at the NRR due to excavation.

Bayonetting: Describes vascular appearance of the vessel as it follows the excavated NRR. Like a pencil in water. Z shape.

Question 18

Vessel baring

Answer 18

Where the NRR used to be. Indicates change and wearing away of the NRR/larger cup.

Question 19

ON changes- asymmetric C/D

Answer 19

0.2 asymmetry is sus

POAG is bilateral but often symmetric

Question 20

ON changes- disc hemorrhages

Answer 20

Drance, flame shape. Leads to PPA and VF defect.

Common in NTG

Question 21

ON changes- vessel changes (4)

Answer 21

1. Nasalization: nasal cup as glaucoma starts, vessel nasalization in progressed glaucoma. They fall off to the side bc the tissue is weak.
2. Arterial attenuation
3. Baring
4. Bayonetting

Question 22

How to evaluate the disc

Answer 22

Small rectangular beam over the nerve

Red free to view ONH and RNFL

Direct medium spot

Question 23

5 R’s

Answer 23

1. Scleral Ring
2. Rim eval using ISNT rule
3. RNFL
4. Region around disc for PPA.
   - Beta is closest to the nerve and appears white due to atrophy of RPE and choriocap. Associated with glaucoma.

• Alpha is further from the nerve and appears dark due to RPE pigment changes. Less associated with glaucoma.
  5. Retinal/disc hemes

Question 24

Lamina cribrosa has how many pores and where are they largest at

Answer 24

400-500 pores. Largest at vertical poles

Larger pores= less structural support. Susceptible to tensile strain and impede axoplasmic flow = glaucoma changes.