Retinal Vascular Occlusion Flashcards
What Changes can DM cause in the eye?
- Diabetic retinopathy
- Cataract
- Vacuolation of the iris pigment epithelium
- Thickening of the ciliary basement membrane
What type of retinal vessels does DR affect?
It is a microangiopathy affecting precapillary arterioles, capillaries, and postcapillary venules.
What abnormalities are seen at the histological level in DR blood vessels?
- Multilayering of the basement membrane
- Degeneration of endothelial cells and pericytes
–> Results in capillary non perfusion and tissue ischaemia
What causes cotton wool spot formation?
Microinfarctions
Swollen ends of interupted axons
What retinal layer are CWS found in?
Nerve fibre layer
What causes hard exudate formation in the retina?
Reduced perfusion to the vascular bed and endothelial damage
What is seen on histology in Hard exudates?
Eisinophilic masses containing foamy macrophages with lipid
Which layer of the reetina are HEs found in?
Deep capillaries - causes plasma leakage to the outer plexiform layer
What causes Microaneurysm formation in DR?
Ischaemia of capillary bed, weakening the wall by necrosis of the pericyte
Which layer of the retina are MAs found?
Superficial capilliaries due to pericyte loss
/Often the INL
Which layer of the retina are Flame haemorrhages found?
Small arterioles causing leakage to the Nerve fibre layer
Which layer of the retina are Dot haemorrhages found?
Capillary rupture in the outer plexiform layer
Which layer of the retina are Blot haemorrhages found?
Capillaries between photoreceptor and RPE
Which type of blood vessels do flame haemorrhages affect?
Small Arterioles
Which type of blood vessels do Dot haemorrhages affect?
Capillaries
Which type of blood vessels do Blot haemorrhages affect?
Capilaries
Where do IRMA usually arise from?
From the venous side of the capillary bed within an are of arteriolar non-perfusion
Where do new vessels form in the retina?
In the prevenular capillaries and venules and proliferate within and on the surface of the retina
In intrauterine life what drives retinal blood vessel growth?
blood vessels grow from the disc towards the periphery driven by a relative hypoxia.
How does prematurity cause retinopathy?
- 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
What happens of ROP is left untreated?
Can lead to bilateral RD
Which part of the retina is usually last to be perfused in a prem infant?
Temporal retina - it is from here in an ischaemic retina that growth factors are produced for NV
Which part of the retina in a prem infant is usually responsible for driving growth factors in an ischaemic retina?
The temporal retina as it is usually lastly perfused in a prem infant
What vessel changes are seen in hypertenisve retinopathy?
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
What can be seen on examination in malignant HTN?
- CWS
- Haemorrhages
- Exudates
- Papilloedema
What is the most likely origin of CRAO?
Emboli - usually from carotid plaque
- Can also be from thrombosis but less common
Why is there a cherry red spot in CRAO?
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
What features of the central retinal vein can increase thrombosis risk?
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.
Which condition is more likely to develop Neovascularisation and rubeosis - CRAO/CRVO?
CRVO - usually within 3 months
