Ocular Vascular Disease

Nonstenotic plaque

Most common type of plaque The buildup projects outwardly, not affecting the diameter of the lumen Angiogram would not reveal abnormalities Thin caps, where can rupture, causing emboli formation May be managed by reducing LDL levels

Stenoic plaque

Plaque projects inwardly, decreasing the diameter of the lumen Thick cap, obstructing blood flow Can be detected in angiography Treated with stents, angioplasty

bruit

The unusual sound created by disturbance in flow from artery narrowing secondary to plaque, stenosis or occlusion Bruit indicates significant stenosis Bruit is not heard if stenosis (narrowing) is less than 80% or is 100%

Vasoconstrictive phase of hypertensive retinopathy

(1st phase): 1. Increase in vascular tone within walls of vessels 2. Occurs in vessels with intact muscular walls and normal autoregulation 3. Goals of vasoconstriction: stabilize internal pressure in vessels, without damaging capillary bed or vessels walls

sustained hypertension phase of hypertensive retinopathy

(2nd phase): 1. If HTN is sustained, will result in compensatory structural changes in arterial walls (arteriolosclerosis) 2. Result is thickening of basement membrane, deposition of collagen within the initima and media of vessel wall—this process is called hyalinization, and marks the sclerotic phase

Sclerotic phase of hypertensive retinopathy

(3rd phase): 1. If pressure within vessel rises acutely or is elevated for a prolonged period, it may exceed limits of vasoconstriction and compensation process of sclerosis 2. In sclerosis, there is lack of muscle tone 3. Permanent narrowing of blood vessels 4. Breakdown of blood retinal barrier, causing leakage of exudates and flame, dot and blot hemorrhages

CRAO with cilioretinal artery sparing

1. 20-30% of eyes have a cilioretinal artery 2. Part of ciliary circulation 3. Supplies the papillomacular bundle—may preserve some central vision a. Wedge shaped area emanating out towards the macula from the optic disc. There is variability in size of ciloretinal artery and area it supplies

Optic Nerve Swelling

1. Associated with accelerated (malignant) hypertension (HTN) a. Blood pressure > 160/110 2. Poor prognosis since these changes can affect the heart, cause renal failure and encephalopathy

What factors control/affect autoregulation of blood flow?

1. Blood flow in autoregulation is regulated by changes in vascular resistance a. Resistance is the inverse of vessel diameter to the fourth power i. Ex., 10% increase in vessel diameter reduces resistance by approx. 40% 2. Autoregulation is controlled by oxygen and carbon dioxide levels within tissue, which create endothelial-derived molecules to modulate vascular tone (thromboxane A2, prostaglandins, nitric oxide) 3. Perfusion pressure: the difference between arterial and venous pressure 4. Ocular perfusion pressure: the difference between arterial and venous pressure minus IOP

Cotton wool spots

1. Caused by acute inner retinal ischemia 2. Occurs in the posterior pole along the radial peripapillary capillary 3. Cotton wool spots are characterized by microvascular infarcts with axoplasmic flow blockage and accumulation of mitochondria and degenerative cell membranes. They indicate obstruction of axoplasmic flow 4. Cotton wool spots disappear after a few weeks, but leave behind defects in the retinal nerve fiber layer when testing visual fields

Optic Nerve Edema

1. Changes to vessels within the disc itself, causing edema, exudates, etc., spilling onto surrounding area 2. Bilateral presentation

Embolic disease

1. Fat and air emboli a. Etiology is controversial—due to cotton wool spots, leukocytes, fat, protein, exudates? b. Occurs following compressive chest injury or fracture of long bones c. Called Purtscher's retinopathy 2. Silicone, cornstarch, talc retinopathy

What types of retinal hemorrhages are associated with systemic HTN?

1. Flame-shaped nerve fiber layer hemorrhages are common in hypertensive retinopathy 2. Dot-blot hemorrhages within the outer plexiform occurs in severe hypertensive retinopathy

Platelet-fibrin emboli

1. Long, dull-white slowly moving "porridge-like" opacities within arterioles a. Can see moving while in office 2. Originates from ulcerating carotid atheromas 3. Result in amaurosis fugax and retinal infarction 4. Seen following cardiac bypass surgery, which can liberate emboli

What are the characteristics of ischemic CRVO?

1. Mean age of onset is 68 years 2. Average acuity is 20/400 at presentation 3. More than 50% capillary nonperfusion and nerve edema 4. Marked venous engorgement, venous tortuosity, hemorrhages, cotton wool spots (more present in nonischemic) 5. Complications: same as CRVO with addition of neovascularization of iris, angle

Cholesterol emboli

1. Yellow-orange, glinting, flat mobile opacities seen at arteriole bifurcation 2. Called Hollenhorst plaques 3. Originates from ulcerating atheroma carotid 4. Temporary, with emboli moving "downstream" 5. May be asymptomatic, transient or permanent vision loss 6. Retinal circulation often not obstructed

What are the characteristics of non-ischemic CRVO?

1. Mild-moderate retinal capillary nonperfusion A. Mean age of onset is 63 years 2. Average visual acuity presentation is 20/50 3. Venous engorgement and retinal hemorrhage in all quadrants 4. Improvement over several months; vein recanalizes 5. Complications: cystoid macular edema, venous shunts on the optic nerve (single, fat, torturous vessel) A. Shunts from normal vascular channels which detour outflow from obstructed venous circulation to choroidal circulation

Exudative phase of hypertensive retinopathy

1. Necrosis develops unless HTN is reduced 2. Necrosis occurs if autoregulation is lost, which results in inability of vasoconstriction to occur, producing capillary bed damage from high pressure 3. Result is impaired flow, ischemia with cotton wool spots and vessel closure

Mechanism causing CRVO?

1. Occlusion of central retinal vein behind or at level of lamina cribosa 2. In that region, both the lumen of Central Retinal Artery (CRA) and Central Retinal Vein (CRV) are more narrow and closer together in a closed environment a. If there is a change in diameter in one of the vessels, the other vessel cannot move to accommodate that change 3. Occlusion is secondary to physical blockage from a thrombus in CRV, but the underlying cause is coming from the adjacent CRA a. CRA has an atheroma within it, pressing up against the CRV, disturbing the flow in vein, causing attraction of platelets and formation of a thrombus i. Turbulence, endothelial damage, platelet aggregation and venous thrombus formation • Occlusion is also seen in abnormalities of blood viscosity where there are too many cellular elements, such as hyperviscosity syndromes

Calcium emboli

1. Originates from calcified aortic valves 2. Large, pearly-white, non-mobile opacity 3. Observed within arteries on optic nerve

Arteriolar light reflex

1. Originates from surface of blood column a. Column of RBCs viewed through transparent wall 2. Normal reflex is approximately 1/5 the width of the vessel a. Reflex varies in normal and can be very bright and broad in young people b. Chronic elevated blood pressure can widen and brighten that reflex if have changes in the transparency of blood vessel wall i. If developing sclerosis, will get abnormal reflex off blood vessel wall. Sclerosis is related to duration of systemic hypertension. ii. Artherosclerosis can change the color of the reflex—copper wire to silver wire appearance—due to no longer looking at blood cells in blood column, but wall has lost its transparency. c. It can be uncertain if the reflex changes are due to alterations in wall transparency (sclerosis) or from changes in hemodynamic flow and velocity changes

Steps of a carotid artery exam

1. Palpate for pulse 2. Listen for bruit (auscultation) a. Listen for disturbance in ocular flow from artery narrowing b. Bruit is heard only if: i. The unusual sound created by disturbance in flow from artery narrowing secondary to plaque, stenosis or occlusion. ii. Bruit indicates significant stenosis iii. Bruit is heard if stenosis (narrowing) is greater than 80% c. However, absence of bruit does not rule out carotid stenosis i. Patients with ulcerative plaques also at risk for stroke ii. Patients with significant carotid stenosis at significant risk for stroke 3. Ateriography 4. Doppler ultrasonography 5. Ophthalmodynamometry 1. Measures systolic and diastolic retinal artery pressure 2. Lower pressure on side of internal carotid artery stenosis

prevalence of hypertension in the US?

1. Systemic hypertension: 50 million US adults 2. 3-18 years old: 2 million children are affected, but 75% are undiagnosed 3. >60% years olds: 90% of will eventually develop HTN

Best ways to grade/ evaluate vessel changes in HTN?

1. Vasoconstriction: seen beyond 2nd arterial branch 2. Sclerosis: may be found even in normal blood pressure 3. Hemorrhage, exudates, cotton wool spots 4. Complications: retinal artery and venous occlusion

Signs of CRVO

1. Venous outflow obstruction causes spillover of hemorrhage into retina, involving all 4 quadrants a. Retinal hemorrhage in vascular retina b. Infarction of nerve fiber layer from ischemia from sluggish arterial flow 2. Sluggish vascular flow because blood cannot flow out, and because new blood cannot get in, will cause ischemia and infarction.

Changes that occur in atherosclerosis?

A. Affects the large and medium sized muscular arteries (E.g. coronary, carotid, aorta, etc.) B. Risks: hypertension, hypercholesterolemia, diabetes, age C. Results in occlusion of vessel lumen from thrombus or plaque with emboli of cholesterol, fibrin and platelets. May result in aneurysm formation. Vascular wall affected. 1. Atheromas are NOT seen in retinal vessels, but may affect central retinal artery - Can see the effect of atheroma, but no distinct lesion D. Changes within the walls of the small arteries and arterioles, called hyalinization (replacement of smooth muscle cells with collagen) E. Affects kidneys, retinal vessels F. Results in narrowing of vessel lumen G. Results in ischemia

What are the steps of plaque formation?

A. Fatty deposits settle B. Fatty deposits increase 1. Sometimes the endothelial area is very thin, leading to an ulcerating plaque where the contents (fibrin, platelets, cholesterol) are liberated to the blood stream, giving rise to cholesterol emboli C. Cap ruptures, causing platelets to adhere, forming a thrombus D. Thrombus enlarges to the point where it completely obstructs the lumen, causing a myocardial infarction if it involves the heart vessels E. Thick cap (no rupture), but as the plaque builds in size, it begins to obstruct the lumen. That by itself can cause adherence of plateletsthrombus

The 4 phases of hypertension's effect on hypertensive retinopathy

A. Vasoconstrictive phase of hypertensive retinopathy B. Sustained HTN C. Sclerotic phase of hypertensive retinopathy D. Exudative phase

In the days and weeks following a CRAO, what changes are seen in the retina?

Acute retinal changes disappear in a month, leaving pale, atrophic optic nerve and attenuated arteries. Late stage CRAO shown here, note pale nerve and reduced AV ratio.

A/V crossing changes

Arteriovenous crossing changes 1. Normal: no change in direction, diameter, color of either the arteriole or venule where they cross each other a. Arteries and veins share a common basement membrane that has collagen fibers, which link the venue and arteriole together where they cross each other 2. Abnormalities: nicking, tapering, compression of venule, changes in path of venule such as S-shaped bends and right angle deflections, banking—all evidence of arteriolosclerosis

Neovascular glaucoma

Associated with CRVO: Neovascular glaucoma more likely the greater the degree of retinal capillary nonperfusion a. Most commonly seen within 3-5 months of onset b. Management: IOP, gonioscopy, funduscopy, fluorescein, angiography, laser photocoagulation, anti-VEGF, corticosteroids, anti-glaucoma medications

What is the proper procedure for taking accurate blood pressure readings?

Blood pressure is variable throughout the day Need a proper cuff size to take measurements Patient should be sitting down, with feet on floor, back supported, arm at heart level. Take two readings and average them. If the difference is 10 mmHg or more, they likely have cardiovascular disease.

BRAO

Branch Retinal Artery Occlusion 1. The result of an emboli 2. Presents as a small area of retinal pallor

BRVO

Branch Retinal Vein Occlusion: 1. Occlusion occurs at same branching of the arteriole and venue at the surface of the retina 2. Wedge-shaped area of retinal hemorrhage 3. Most common in superior-temporal retina 4. Occurs at AV crossings, where A & V share glial sheath 5. With gravity, some of hemorrhage and edema will sweep down and affect the macula a. Many be asymptomatic since it may not cloud macula 6. Collaterals in BRVO a. Interconnecting vessels shunts 7. Management: observation, laser for macular edema and treat underlying systemic disorder

Most common cause of CRAO?

Embolus is the most common cause a. Carotid artery disease due to atherosclerotic plaque b. Carotid stenosis and heart are other sources of emboli

HCRVO

Hemiretinal vein occlusion (HCRVO): ***20% of eyes have venous branches drain superior and inferior retina and then enter lamina separately before forming single CRV*** a. Occlusion in one branch results in retinal hemorrhages in superior or inferior half of retina

blood flow autoregulation: what is it, and which tissues does it affect?

In autoregulation, physiological mechanisms which maintains blood flow and tissue oxygen, despite alterations in perfusion pressure. Retina and optic nerve vascular beds, anterior to lamina cribosa, are under autoregulation

What causes the "retinal pallor" associated with CRAO?

Inner 2/3 of retina is supplied by CRA (first intraorbital branch of ophthalmic artery) and outer 1/3 of retina (RPE and photoreceptors) is supplied by choroid (ciliary arteries which originate from ophthalmic artery, a branch of the internal carotid artery) a. Inner 2/3 of retina will look pale in color in CRAO because less blood is coming into region. It is like one giant cotton wool spot because there is ischemia everywhere.

Where does CRAO occur?

Occlusion of the CRA occurs within the lamina, within the narrowest part of CRA dural shealth of optic nerve.

What is a symptom that might precede a CRAO?

Onset may be preceded by transient monocular loss of vision (amaurosis fugax)

amaurosis fugax

Onset of CRAO may be preceded by transient monocular loss of vision called amaurosis fugax: i. Symptoms last 2-10 minutes, but can last 2-3 hours ii. Vision always returns to normal after each episode iii. Other causes include temporal arteritis and migraines iv. May be associated with TIA v. Requires STAT referral

Exudates

The result of endothelial cell damage with leakage and selective reabsorption and residual lipids within the outer plexiform layer (pretty sure this is exudates but it could be vessel sheathing?)

Vessel Sheathing

This anterior surface of the vessel has glial cell proliferation. This is secondary to inflammation associated with vascular damage typically from emboli

Carotid Artery Disease (ocular manifestations)

Transient monocular loss of vision (amaurosis fugax) (transient ischemic attack) often a symptom in carotid artery disease a. The result of emboli from atheroma in carotid artery b. Episodes described as "darkening" or "dimming" of vision, or vertical "curtain pulled" over vision i. If occurs in clusters, suggests multiple emboli c. Amaurosis fugax

How soon must CRAO be caught/treated in order to save vision?

Unless CRAO can be caught within the first 4 hours, there is no possibility that they can recover vision.

Signs of CRAO?

a. Acute CRAO is a retinal infarct, retinal edema, and retinal pallor within 30 minutes b. Because the retina is thin at the fovea, "cherry red spot" seen is the normal choroidal vasculature underlying fovea. c. Arteriole narrowing d. Segmentation in arterial and venous flow in acute stage e. Afferent pupillary defect (APD) f. No light perception or vaguely make out hand motions

Risk factors for CRAO?

a. HTN, DM, high cholesterol, smoking b. Cardiac valvular disease, atrial fibrillation c. Vasculitis (giant cell arteritis), thrombus d. IV drug use e. Thrombophilic disorders (platelet abnormalities, estrogen) f. Vasospasms (migraines)

Risk factors for CRVO

a. HTN, diabetes, hyperviscosity syndromes, platelet abnormalities, hyperlipidemia, estrogen preparations, and smoking. b. Primary open angle glaucoma or ocular hypertension seen in 40-70% of CRVO patients c. Consider lowering IOP in non-CRVO eye as prophylactic treatment

Management of CRAO?

a. Ocular emergency with immediate attempts to dislodge presumed emboli downstream by: i. Raising and lowering IOP through paracentesis (anterior chamber aqueous release), ocular massage, and breathing in paper bag (CO2 results in vasodilation, O2 results in vasoconstriction) b. Medical evaluation for systemic involvement i. Patients with retinal vascular observations are at a significant risk of stroke with reduced life expectancy

What are the manifestations of target-organ disease in peripheral vascular disease?

absence of major pulse in extremities 1. Claudication: pain in exercising muscle from decreased blood flow from arteriosclerosis

What are the manifestations of target-organ disease in the cardiac system?

myocardial infarction 1. Monitor signs, symptoms, EKG, angiography, lab tests for cardiac disease

Attenuation

narrowing of arterioles: 1. Vasoconstriction produces narrowing of caliber of vessels which affects the AV ratio 2. Narrowing-construction depends on severity, duration, and rapidity of hypertension a. Can be focal or diffuse changes 3. Normal AV ratio: artery is 2/3-3/4 the width of venule. However, is difficult to evaluate AV ratio due to quadrant variation a. Attenuation doesn't give information on duration of HTN or even if it is HTN. Diffuse attenuation could be due to chronic, current, or previous HTN.

Two inflammatory markers used to evaluate those at risk of high cholesterol?

o C-reactive protein 1 mm/L : low risk for inflammation >3 mm/L: high risk for inflammation o PLAC test (Lp-PLA2)

What lipid levels are considered healthy/ normal for LDL, HDL, total cholesterol?

o LDL <100 LDL: Lipoprotein that has more cholesterol than protein o HDL >40 HDL: Lipoprotein that has more proteins than cholesterol o Total cholesterol <200

atheroma

plaque: develops in the subendothelial space, can expand within the lumen of the vessel or outward

What is atherosclerosis?

progressive inflammation forms plaques (called atheroma-composed of cholesterol and other inflammatory agents) within the intima of blood vessels o Driving force is constant cycle of inflammation o There is damage where immune cells "ingest" "bad" cholesterol, which then become trapped in arterial walls, contributing to plaque buildup

What are the manifestations of target-organ disease in the retina?

retinopathy, cotton wool spots, hemorrhages, exudates

What are the manifestations of target-organ disease in renal disease?

serum creatinine, blood urea nitrogen, proteinuria

perfusion pressure

the difference between arterial and venous pressure

ocular perfusion pressure

the difference between arterial and venous pressure minus IOP

What are the manifestations of target-organ disease in the cerebrovascular system?

transient ischemic attack 1. Transient ischemic attack: Brief episode of neurological dysfunction caused by brain or retinal ischemia; lasts 1 hour or less, then return to normal. No evidence of cerebral or retinal infarction

A/V ratio is reduced (~1/3), arterial reflex is taking over the entire vessel, and there is venous nicking

what vascular changes can you see?

what is "hypertensive disease"?

when hypertension begins to affect target organs: kidney, brain, heart, eyes