2.26 retinal vasculature

Blood pressure categories?

Normal less than 120 and less than 80

Elevated 120-129 and <80

HTN stage 1 130-139 or 80-89

HTN stage 2 140 or higher or 90+

Hypertensive crisis >180 and/or >120

Risk of CV disease doubles for ...

every increase of 20 points over 115 for systolic and 10 for diastolic over 75

Peripheral vascular disease results in what?

- absence of major pulse in extremities

- claudication (pain in exercising muscle from decreased bloodflow)

Arteriosclerosis

hardening/thickening of artery wall with loss of elasticity

Atherosclerosis definition

progressive inflammation of arterial walls with accumulation of lipids and thickening of wall

- this is a type of arteriosclerosis

Atheroma (Plaque)

develop in sub-endothelial space which expands outward as well as inward

LDL target -- good or bad?

HDL target -- good or bad?

<100 -- bad

>40 -- good

To gauge amount of atherosclerosis, how?

do some inflammatory marker blood tests

Are atheromas seen in retinal vessels?

no but can affect central retinal artery

When it comes to arteriosclerosis, how can hyalinization occur ?

- accumulation of collagen in walls of small arteries/arterioles which is seen in the retina resulting in narrowing of the vessel lumen and ischemia

Retina and optic nerve vascular beds, anterior to lamina cribrosa, are under __________

autoregulation

What is autoregulation?

physiologic mechanism designed to meet metabolic demands (O2/CO2 balance) by maintaining bloodflow and tissue oxygen despite alterations in perfusion/arterial pressure

Are choroidal vascular beds under autoregulation? how do they work?

no, choroidal vessels are fenestrated with no blood-ocular barrier

Perfusion pressure is defined as ...

bloodflow to maintain metabolic/nutritional requirements

What is ocular perfusion pressure? is it constant or variable from day to night?

pressure at which blood enters the eye -- highly variable

In retinal vasculature, what is the initial response to HTN in normal non sclerotic vessels?

arterial-arteriolar vasoconstriction (vasospasm) of smooth muscle in vessel walls (to reduce flow), especially if there is a high O2 percentage b/c that tells the autoregulation that the BP is too high

As a result of hypertensive retinopathy, there eventually is what?

retinal blood barrier breakdown

Sclerotic Phase of HTN in eye? (next after initial effects)

- compensatory structural changes (arteriosclerosis) in arterial walls

- result is thickening of basement membrane, muscle is replaced by collagen with narrowing of lumen resulting (hyalinization)

- as a result, BVs can no longer become narrower or wider

Is the narrowing from sclerotic phase reversible or irreversible in retinal BVs?

irreversible

Sclerotic Phase of HTN -- what are the retinal changes?

- lack of muscle tone

- breakdown of autoregulation

- breakdown of Blood retinal barrier

- flame, dot, blot hemorrhages

- plasma lipoproteins seen as hard exudates

What occurs in the exudative phase of HTN?

- necrosis develops unless BP reduced

- capillary beds are damaged when autoregulation is lost

- impaired flow, ischemia, and CWS

Phases of HTN?

- Initial

- Sclerotic

- Exudative

Retinal vasculature HTN changes?

- attenuation of arterioles

- AV ratio changes

- arteriolar light reflex change

- AV crossing changes

- flame/dot/blot retinal hemorrhages

- CWS

- Exudates

- Vessel sheathing

- ONH swelling

Normal AV ratio?

artery is 2/3 to 3/4 the size of venule

Normal arteriolar light reflex/what happens with increased BP?

- approx 1/5 width of vessel

- reflex is widened and brightened

Sclerosis is related to _______ of systemic HTN?

duration

Attenuation can be _____ or ______

focal or generalized

AV crossing changes cause?

thickened arteriole crosses over venule and compresses it

Salus's sign

deflection of retinal vein as it crosses arteriole

Gunn's sign

tapering of retinal vein on either side of AV crossing

CWS disappear in how long?

4-6 weeks

Optic nerve swelling is associated with ...

accelerated (malignant) HTN

What can mimic Hypertensive retinopathy?

- diabetic retinopathy

- retinal venous obstruction

- hyperviscosity syndrome

- ocular ischemic syndrome

- radiation retinopathy

Retinal vein occlusion 2 biggest risk factors

HTN and hyperlipidemia

How does CRVO occur?

- atherosclerosis of adjacent central retinal artery compresses central retinal vein at lamina cribrosa leading to thrombosis in vein (occlusion, endothelial damage, platelet aggregation, venous thrombus formation)

Does CRVO usually present bilaterally or unilaterally?

unilateral

2 types of CRVO

Nonischemic and ischemic

Nonischemic CRVO

- characterized by what?

- avg VA at presentation?

- complications

- mild-moderate retinal capillary perfusion

- 20/50

- cystoid macular edema, venous shunts

is avg age of onset in nonischemic or ischemic CRVO higher?

ischemic CRVO

Ischemic CRVO

- avg VA presentation?

- characterized by...

20/400

more than 50% capillary nonperfusion and nerve edema

Ischemic CRVO

- retinal findings

- complications

- marked venous engorgement, venous tortuosity, hemorrhages, CWS

- cystoid macular edema, optociliary shunts, neovascularization

In CRVO, neovascular glaucoma is more likely the greater the ...

degree of retinal capillary nonperfusion

Risk factors for CRVO

- HTN, hyperlipidemia, diabetes, hyperviscosity of blood

In 40-70% of CRVO patients, what is seen?

primary open angle glaucoma or ocular HTN

Branch retinal vein occlusion is most common in what part of retina?

superior temporal retina

BRVO symptoms

many are asymptomatic

BRVO management

observation, laser for macular edema

Central retinal artery occlusion (CRAO)

- mainly caused by what?

- form of what?

- thromboembolism or local thrombus formation of Central retinal artery at lamina cribrosa (narrowest part of CRA)

- acute ischemic stroke

CRAO is associated with ...

life threatening stroke and CV diseases

emboli from the heart

Main risk factors for CRAO

Obesity, HTN, smoking, hypercholesterolemia (high cholesterol)

CRAO

- symptoms?

- sudden painless loss of vision

- RAPD

- evidence of retinal hypofusion

95% of CRAO are classified as what?

5% of CRAO are classified as what?

nonarteritic

arteritic (disorder of giant cell arteritis)

CRAO what are the main sources of emboli?

- carotid artery disease

- emboli from heart

Inner 2/3 of retina supplied by _____

Outer 1/3 of retina (RPE and photoreceptors) supplied by ______

CRA

choroid

Main clinical observations of retina of CRAO

- retinal pallor

- cherry red spot on fovea

- arteriole attenuation

- boxcarring (slow segmental bloodflow)

In majority of CRAO how does ONH look?

normal

Why would acuity be nearly normal in CRAO case?

in presence of a cilioretinal artery (which occur in 20-32% of eyes--congenital)

What is the retinal ischemic tolerance time?

4 hours

CRAO risk factors

HTN, DM, high cholesterol, smoking, giant cell arteritis

When you see optic disc edema in CRAO, suspect what?

arteritic CRAO

CRAO management

- immediate referral to ER

- ant chamber paracentesis (aqueous release of ant chamber to raise and lower IOP quickly--attempts to dislodge emobli)

- ocular massage

- CO2/O2 combo

CO2 results in _______

O2 results in _______

vasodilation

vasoconstriction

Carotid artery disease

- what is usually the main symptom?

- transient monocular loss of vision (amaurosis fugax) TIA

Hollenhorst plaques (cholesterol emoblis) in retina can indicate what?

carotid artery disease

Cholesterol emobli in retina

- describe typical presentation

temporary with emboli moving downstream

asymptomatic, transient, or permanent vision loss

retinal circulation often not obstructed

Calcium emboli

- describe typical presentation

- large pearly white nonmobile opacity

- observed within arteries or optic nerve

- originate from calcified aortic. valves

Platelet-fibrin emboli

- describe these

- long, dull white slowly moving opacities within arterioles

- originate from ulcerating carotid atheromas

- result in amaurosis fugax and retinal infarction

Fat and air emboli

- describe these

- cause controversial

- called purtscher's retinopathy

what is bruit

sound indicating blood flow turbulence secondary to plaque, stenosis, occlusion

it's not heard if stenosis is less than 80 or 100%

focal attenuation of arterioles

widening of venule light reflex

Which is more seveere copper wire light reflex or silver light reflex?

silver light reflex

nonischemic CRVO and ischemic CRVO

hemiretinal vein occlusion (HRVO)

branch retinal vein occlusion (BRVO)

CRAO

boxcarring