A2. Arterial & venous occlusive disease

Question 1

what is an embolism?

Answer 1

condition whereby an intravascular mass is dislodged at the point of origin and carried by blood to a distant site (normally at arteries)

Question 2

what are the 2 artery occlusive diseases that can be caused by embolisms? define them

Answer 2

BRAO: Branch retinal artery occlusion (BRAO) blocks the small arteries in your retina.

CRAO :blockage in the central artery in your retina. This is a form of a stroke in the eye and must be evaluated and treated immediately, just like a stroke

Question 3

what is an arterial occlusive disease?

Answer 3

a blockage in one or more of the arteries of your retina. The blockage is caused by a clot or occlusion in an artery (emoblism), or a build-up of cholesterol in an artery. This is similar to a stroke.

Question 4

describe the classic appearance of CRAO. what are the 10 signs and symptoms?

Answer 4

Cherry red-spot (reddish foveola on pale retina, due to choroidal blood circulation below the fovea). Embolus too big, lodged at laminar region

1. Early attacks of amaurosis fugax (sudden, temporary loss of vision)
2. Sudden painless loss of vision to LP (light perception) or CF (counting fingers) over seconds
3. RAPD
4. Arterial attenuation/narrowing
5. Venous stasis
6. Retinal haze/ischemia
7. Within hours the retina whitens with a cherry red spot (due to choroidal layers seen through thin fovea)
8. Visual field defect
9. Optic atrophy
10. Presence of cilioretinal artery can maintain macular function, also term as “macular sparring” (CRA supply blood to macular, preserving central vision)

Question 5

Mx for CRAO?

Answer 5

Rapid intervention, within 90 minutes (immediate referral)

Treatment includes reducing IOP, vasodilation (dilate blood vessel to increase oxygen supply and possibly dislodge the emboli), surgical removal of emboli

Question 6

describe the classic appearance/etiology of BRAO. what are the 5 signs and symptoms?

Answer 6

Similar to that of CRAO with better visual prognosis to 6/12 or better
Embolus small enough to pass through the laminar region and lodged at arterial branch
Common at superotemporal retina

1. Early attacks of amaurosis fugax
2. Distribution is dependent on the location of affected b/v
3. Arterial attenuation/narrowing
4. Retinal haze/ischemia
5. Within hours the retina whitens because of hypoxia (areas affected by that artery)

Question 7

Mx for BRAO?

Answer 7

Rapid intervention, within 90 minutes (immediate referral)

Treatment includes reducing IOP, vasodilation (dilate blood vessel to increase oxygen supply and possibly dislodge the emboli), surgical removal of emboli

SAME AS CRAO!!

Question 8

what is a thrombus?

Answer 8

A thrombus is a blood clot that forms in a vein

comparing to an embolus:
An embolus is anything that moves through the blood vessels until it reaches a vessel that is too small to let it pass.

Question 9

what are the 2 venous occlusive diseases that can be caused by thrombus? define them

Answer 9

BRVO: thrombus occurs at arteriovenous crossing point secondary to atherosclerosis of the retinal artery causing compression and occlusion of the retinal vein.

CRVO: thrombus occludes the central retinal vein near lamina cribosa. May be further classify into Non-ischemic & ischemic

Question 10

what are the 5 risk factors for venous occlusive diseases?

Answer 10

1. Age – 50% of cases occur in patients >65yo
2. Hypertension–present in more than two-thirds of patients >50yo and 25% in younger patients–particularly in BRVO
3. Hyperlipidemia – present in one-third or more of patients
4. Diabetes mellitus – presents un up to 15% of patients >50yo \
5. Glaucoma & ocular hypertension, associated with higher risk of CRVO

Question 11

what is the common cause of BRVO? name 10 SSx

Answer 11

Most common cause - systemic hypertension

Symptoms:
Depending on location of occlusion.
1. –If macula involved - sudden painless onset of blurred vision and metamorphopsia
2. –if peripheral - asymptomatic

Signs (Distribution is dependent on the location of occlusion):
3. Dilation and tortuosity of affected region
4. Flame-shaped haemorrhages
5. Dot-blot haemorrhages
6. Retinal and/or macular oedema
7. Cotton Wool Spots (CWS)
8. Commonly superotemporal quadrant
9. Retinal neovascularisation in 8% of eyes by 3 years.
10. NVD (Neovascularisation at disc), NVE (Neovascularisation elsewhere) possible, which is a risk of tractional retinal detachment. NVE more common than NVD

Question 12

what is the prevalence of non-ischemic CRVO? progression? name 8 SSx

Answer 12

75% of CRVOs (more common than ischemic form), around one-third will progress into ischemic CRVO

Symptoms:
1. Sudden painless monocular decrease in vision
2. VA variable depending on severity. Eyes with initial good VA tend to have good prognosis. Patients with VA worst than 6/60 indicates substantial ischemia present.
3. RAPD - absent or mild

Signs:
4. Dilated and tortuous veins
5. Flame-shaped haemorrhages
6. Dot-blot haemorrhages
7. Optic disc and macular edema
8. Cotton-wool patches (particularly in hypertensive patients)

Question 13

what is the main characteristic of ischemic CRVO? what is the prevalence? name 11 SSx

Answer 13

Characterized by rapid onset venous obstruction resulting in decreased retinal perfusion, capillary closure and retinal hypoxia
­~25 % of CRVOs­

Symptoms:
1. sudden and severe monocular painless visual impairment
2. VA usually counting fingers, visual prognosis poor due to macular ischemia­
3. RAPD­ present

Signs:
4. “blood & thunder” fundus
­5. severe tortuosity & engorgement of vein
6. extensive flame-shaped haemorrhages
­7. extensive dot haemorrhages ­
8. cotton-wool spots
9. severe disc swelling and hyperaemia­
10. NVI (neovascularisation at iris)/rubeosis iridis develops in 50% of eyes usually around 2-4 months (“90-day glaucoma”)
11. retinal neovascularization occurs in 5% of eye, less common than BRVO

Question 14

how do we ddx ischemic CRVO and non-ischemic CRVO? what are the 4 tests to be conducted?VPRE

Answer 14

1. Visual acuity – ­‘if an eye with CRVO has 20/400 or worse vision, then there is about a 90% chance that that eye has ischemic CRVO’
2. Peripheral visual field: ­non‐ischemic CRVO = sensitive to small & dim target (I-2e) ­ischemic CRVO’ = only able to see large & bright target (I-4e)
3. RAPD – ­Non‐ischemic CRVO, 97% of the eyes had a relative afferent pupillary defect of <0.6 log units.­Ischemic CRVO, 94% of the eyes had a relative afferent pupillary defect of >0.9 log units
4. electroretinography (ERG) – ‘best sensitivity and specificity to differentiate ischemic from non‐ischemic CRVO was amplitude of the b‐wave’

Question 15

Mx for BRVO and CRVO?

Answer 15

-Anticoagulants used to prevent thrombus propagation
-Panretinal photocoagulation (PRP) to prevent neovascularisation