1-11 RVD - BV Occlusions

Question 1

• Structural differences between arteries and veins?
• 3 types of arteriosclerosis? Describe them.

Answer 1

Arteries:
- Smaller lumen controls BP
- Thick muscular layer controls constriction/dilation
Veins
- Thick tunica external for support to store lots of blood
- Valve prevents backflow

Atherosclerosis:
- Larger arteries affected, plaques form (atheroma) which narrows lumen.

Arteriolosclerosis:
- Hyaline arteriolosclerosis due to deposition of hyaline. Hyaline accumulates causing excessive ECM production by smooth muscle cells. This is thought to be normal w/ aging but more prominent in hypertension and diabetes.
- Hyperplastic arteriolosclerosis due to excessive smooth muscle cell count. Likely as response to sudden and persistent BP raise (malignant hypertension of >200/120mmHg)

Question 2

Describe arterial supply to retina

Answer 2

• CRA = inner 2/3 retina
• sPCAs = outer retina
  Anomalous cilioretinal artery/s derived from sPCA can enter retina and be part of retinal vasculature.

Question 3

Central Retinal Artery Occlusion
- Types of emboli?
- Signs/symptoms?

Answer 3

• CRA acutely blocked. Infarcts retinal cells
• Most cases due to atherosclerosis-related embolism or thrombosis.
  – Cholestrol embolus (bright orange spot)
  – Platelet-fibrin embolus (dull white, highlights artery)
  – Calcific embolus (bright white spot)
  – Thrombus
• CRA is a common site due to direct route from ICA

Symptoms:
- Sudden, profound, painless unilateral vision loss
– Central vision can be spared if cilioretinal sparing.
- Transient vision loss after sudden vision loss (amaurosis fugax) from few seconds to several min. Type of transient ischaemic attack (TIA) on eye.
Signs:
- RAPD. Can be profound or total (amaurotic pupil).
- Severe retinal arteriolar attenuation + narrowing I.e. cattle-trucking
- Retina appears white/pale (ischaemia) and cloudy/opaque (oedema) due to RNFL ischemia causing oedema and opacificaiton.
- Cherry red spot at macula since rely on choroid vasculature but may disappear as progresses.
- Emboli may be visible, especially at bifurcation points.

Question 4

Describe Branch Retinal Artery Occlusion

Answer 4

Branch Retinal Artery Occlusion except only part of retina is affected.
- Obstructs branch of CRA (usually temporal due to presentation bias)
- Altitudinal/sectoral VF loss (If central spared, may be not noticed)
- Same signs as CRAO but on one side.

Question 5

Describe retinal venous drainage

Answer 5

Inner retina -> branch retinal veins + venules -> CRV
Outer retina + choroid -> Vortex veins of choroid -> Sup. + Inf. ophthalmic veins
- CRV + ophthalmic veins -> Cavernous sinuses
Note: CRV emerges from ONH meningeal sheath parallel + countercurrent to CRA

Question 6

Central Retinal Vein Occlusion

Answer 6

• CRV occlusion -> blood stagnation -> retinal hypoxia
• Likely due to CRV compression due to CRA arteriolosclerotic thickening which pushes the CRV next to it.
• Blood turbulence, stasis, thrombotic build-up (clots)
• High pressure damages tight junctions and breaches BRB of retinal capillaries causing blood, fluid, and protein leakage.
• Capillary non-perfusion + ischaemia.

Question 7

2 classifications of CRVO?
Differentiation how?

Answer 7

Non-ischaemic vs Ischaemic:
- 6/60 better vs worse
- RAPD mild vs marked
- Vein tortuousity + engorgement variable vs marked
- Dot/flame haemorrhages periphery mostly vs central involved
- CWS occasional vs plenty
- Oedema moderate vs severe

Fluorescein angiography.
Non-ischaemic CRVO shows:
- Arteriovenous phase = Good background fluorescence due to still having blood go to retina
- Venous phase = Hypofluorescence of veins + hyperfluorescence of leakage areas
- Later (recirculation) phase = Oedematous areas highlighted.
Ischaemic CRVO shows:
- Non-perfusion = No background fluorescence due to retina receiving no blood.

Question 8

Describe Branch Retinal Vein Occlusion

Answer 8

• Like CRVO but at branch of CRV
• Either major (one quadrant), macular, or peripheral
• VA depends on macular drainage involvement
• Most common at superior temporal quadrant where AV crossing’s more prominent.

Question 9

RVO risk factors?

Answer 9

• Age increasing (arteriosclerotic changes)
• Underlying systemic conditions (e.g. hypertension, hyperlipidemia, CVD, DM, smoking, obesity)
• High IOP
• Blood abnormalities/disorders