Retinal Vascular Occlusion

Question 1

What Changes can DM cause in the eye?

Answer 1

• Diabetic retinopathy
• Cataract
• Vacuolation of the iris pigment epithelium
• Thickening of the ciliary basement membrane

Question 2

What type of retinal vessels does DR affect?

Answer 2

It is a microangiopathy affecting precapillary arterioles, capillaries, and postcapillary venules.

Question 3

What abnormalities are seen at the histological level in DR blood vessels?

Answer 3

• Multilayering of the basement membrane
• Degeneration of endothelial cells and pericytes

–> Results in capillary non perfusion and tissue ischaemia

Question 4

What causes cotton wool spot formation?

Answer 4

Microinfarctions
Swollen ends of interupted axons

Question 5

What retinal layer are CWS found in?

Answer 5

Nerve fibre layer

Question 6

What causes hard exudate formation in the retina?

Answer 6

Reduced perfusion to the vascular bed and endothelial damage

Question 7

What is seen on histology in Hard exudates?

Answer 7

Eisinophilic masses containing foamy macrophages with lipid

Question 8

Which layer of the reetina are HEs found in?

Answer 8

Deep capillaries - causes plasma leakage to the outer plexiform layer

Question 9

What causes Microaneurysm formation in DR?

Answer 9

Ischaemia of capillary bed, weakening the wall by necrosis of the pericyte

Question 10

Which layer of the retina are MAs found?

Answer 10

Superficial capilliaries due to pericyte loss

/Often the INL

Question 11

Which layer of the retina are Flame haemorrhages found?

Answer 11

Small arterioles causing leakage to the Nerve fibre layer

Question 12

Which layer of the retina are Dot haemorrhages found?

Answer 12

Capillary rupture in the outer plexiform layer

Question 13

Which layer of the retina are Blot haemorrhages found?

Answer 13

Capillaries between photoreceptor and RPE

Question 14

Which type of blood vessels do flame haemorrhages affect?

Answer 14

Small Arterioles

Question 15

Which type of blood vessels do Dot haemorrhages affect?

Answer 15

Capillaries

Question 16

Which type of blood vessels do Blot haemorrhages affect?

Answer 16

Capilaries

Question 17

Where do IRMA usually arise from?

Answer 17

From the venous side of the capillary bed within an are of arteriolar non-perfusion

Question 18

Where do new vessels form in the retina?

Answer 18

In the prevenular capillaries and venules and proliferate within and on the surface of the retina

Question 19

In intrauterine life what drives retinal blood vessel growth?

Answer 19

blood vessels grow from the disc towards the periphery driven by a relative hypoxia.

Question 20

How does prematurity cause retinopathy?

Answer 20

• In a prem infant on supplemental oxygen, the hypoxic drive is reduced and hence the extension of the normal vascular bed is inhibited
• When the baby returns to normal O2 levels, extensive proliferation occurs
• Additionally, the peripheral non vascularised retina is ischaemic further driving neovascularisation from the peripheral vessels growing rapidly and in a disorganised manner in the retina and vitreous

Question 21

What happens of ROP is left untreated?

Answer 21

Can lead to bilateral RD

Question 22

Which part of the retina is usually last to be perfused in a prem infant?

Answer 22

Temporal retina - it is from here in an ischaemic retina that growth factors are produced for NV

Question 23

Which part of the retina in a prem infant is usually responsible for driving growth factors in an ischaemic retina?

Answer 23

The temporal retina as it is usually lastly perfused in a prem infant

Question 24

What vessel changes are seen in hypertenisve retinopathy?

Answer 24

Hyalinization of blood vessels leading to ‘copper silver wiring’ appearance

In more advanced disease:
- Narrowing of the blood vessels and spasm leads to ischaemia on the endothelial cells more distal to the constriction

• As the endothelium degenerates –>fibrin leakage into the vessel –> further narrowing
• Causes Fibrinoid necrosis of choroidal and retinal vessels
• If Choriocapilaries affected = Elschnig’s spots and siegrist streaks formation

Question 25

What can be seen on examination in malignant HTN?

Answer 25

• CWS
• Haemorrhages
• Exudates
• Papilloedema

Question 26

What is the most likely origin of CRAO?

Answer 26

Emboli - usually from carotid plaque

• Can also be from thrombosis but less common

Question 27

Why is there a cherry red spot in CRAO?

Answer 27

In CRAO, the retina becomes opaque following infarction - this prevents transmission of the red reflex from the choroid

The macula is spared due to foveal thinness and lack of neuronal tissue - allowing view of choriocapillaries creating a cherry red spot

Question 28

What features of the central retinal vein can increase thrombosis risk?

Answer 28

The radius of the CRV at the lamina cribrosa is 50% of the prelaminar part of the disc and smaller than the retrolaminar portion

The resistance provided by the venous narrowing increases flow in the narrowed segment, leading to turbulence and an increased risk of thrombosis.

Question 29

Which condition is more likely to develop Neovascularisation and rubeosis - CRAO/CRVO?

Answer 29

CRVO - usually within 3 months