Retinal Vascular Diseases Part 2

Flashcards covering vocabulary and key diagnostic signs for Retinal Vein Occlusions, Retinal Artery Occlusions, Hypertensive Retinopathy, and Retinopathy of Prematurity.

pathogenesis of retinal vein occlusions

arteriosclerosis is an important causative factor for BRVO and CRVO.

in turn causes hypoxia of the retina drained by the obstructed vein

Arteriolosclerosis

Thickening and hardening of the arteriolar walls, which can compress the corresponding vein sharing a common adventitial sheath.

Common predisposing factors of RVO

1. Advancing age

2. hypertension

3. hyperlipidaemia

4. diabetes mellitus

5. raised intraocular pressure

6. oral contraceptive pills

Collaterals

Active remodeling of non-functional vascular network to bypass the site of obstruction and preserve the retinal tissue that is affected by ischaemia.

Branch Retinal Vein Occlusion (BRVO) Signs

• VA is variable - dependent on extent of macular involvement

• Dilatation and tortuosity of the venous segment further to the site of occlusion, attenuation closer to occlusion

• flame-shaped, dot and blot haemorrhages, retinal oedema, and cotton wool spots

course of BRVO

acute features take 6-12 months to resolved and replaced with:

• hard exudates, venous sheathing and sclerosis

• collaterals which may be local / develop across the horizontal raphe

prognosis of BRVO

reasonably good

within 6 months 50% have 6/12 or better VA

management of BRVO

refer to ophthalmologist to monitor for sight-threatening conditions (e.g. macular oedema & neovascularisation)

Non-ischaemic Central Retinal Vein Occlusion (CRVO)

The most common type of CRVO presenting with sudden, unilateral blur vision (sudden painless loss of vision)

Signs of Non-ischaemic CRVO

VA: moderate to severe reduction

APD: absent / mild

tortuosity and dilation of all branches of CRV

dot and blot, flame-shaped haemorrhage, disc & macular oedema, variable cotton wool spots

Afferent Pupillary Defect (APD)

A condition where both pupils are equal in size, but when the affected eye is stimulated by light, neither pupil reacts; however, when the normal eye is stimulated, both react normally.

Prognosis of Non-ischaemic CRVO

• reasonably good, 50% return to normal / near normal vision

• conversion to ischaemic CRVO in 15% of cases in 4 months & 34% of cases in 3 years

Management of Non-ischaemic CRVO

refer to ophthalmologist to monitor for conversion to ischaemic CRVO

• treatment of macular oedema with intravitreal steroid / anti-VEGF

Ischaemic Central Retinal Vein Occlusion (CRVO)

Characterised by rapid onset venous obstruction resulting in decreased retinal perfusion, capillary closure, and retinal hypoxia

Presentation of Ischaemic CRVO

sudden and severe visual impairment

Signs of Ischaemic CRVO

VA: usually counting finger worse

APD: marked

Severe tortuosity & engorgement of all branches of the CRV, extensive dot & blot and flame-shaped haemorrhages

cotton wool spots may be present

Complications of Ischaemic CRVO

• may lead to profound vascular leakage, rubeosis iridis & neovascular glaucoma

• fibrovascular membrane develops on the retina and contracts progressively, which may lead to tractional retinal detachment

Tractional Retinal Detachment

Separation of the neurosensory retina from the RPE (retinal pigment epithelium) by the contraction of a fibrovascular membrane in the absence of a retinal break.

Rubeosis iridis

The development of neovascularisation at the iris, occurring in $50\%$ of eyes with ischaemic CRVO between 2 and 4 months.

Prognosis of Ischaemic CRVO

• most acute signs resolve over 9-12 months

• extremely poor due to macular ischaemia

• rubeosis iridis develops in 50% of eyes between 2 and 4 months (causing neovascularisation glaucoma)

Management of CRVO

refer to ophthalmologist urgently for eyes with rubeosis iridis for laser pan-retinal photocoagulation (PRP)

Retinal Artery Occlusions

Atherosclerosis-related thrombosis at the level of the lamina cribosa (by far most common underlying cause if CRAO)

Risk factors of atherosclerosis

1. age

2. hypertension

3. diabetes

4. raised levels of LDL cholesterol

5. obesity

6. smoking

7. sedentary lifestyle

Carotid Embolism

The origin of the emboli is most often an atheromatous plaque at the carotid bifurcation

The emboli may be of the following types:

• Cholesterol

• Calcific

• fibrin-platelet

Hollenhorst plaques (Cholesterol)

Minute, bright, refractile, golden to yellow-orange cholesterol crystals often found at vessel bifurcations.

Calcific

single, white, non-scintillating particles

Fibrin-platelet

dull grey, elongated particles that may cause amaurosis fugax, occasionally complete obstruction

BRAO

CRAO

Amaurosis fugax

Painless transient monocular loss of vision, often caused by fibrin-platelet emboli.

Branch Retinal Artery Occlusion (BRAO) Presentation

Presents with sudden, profound altitudinal or sectoral VF loss

Signs of BRAO

• narrowing of arteries & veins with sludging and segmentation of blood column

• cloudy white retina that corresponds to the area of Ischaemia

• emboli may be present

Embolic inferotemporal branch retinal artery occlusion

Prognosis of BRAO

• poor unless obstruction can be relieved within a few hours

• VF defect is permanent while the affected artery remains attenuated

Segmentation

The sludging and breaking up of the blood column within a vessel, also known as 'cattle trucking' or 'boxcarring'.

Cherry-red spot

An appearance in CRAO where an orange reflex from the intact choroid stands out at the thin fovea in contrast to the surrounding pale, cloudy retina.

Cilioretinal artery

A vessel present in $20\%$ of the population that arises from the posterior ciliary circulation to supply the macula and papillomacular bundle.

Central Retinal Artery Occlusion (CRAO) Management

Considered an emergency requiring immediate referral to the emergency department (less than $48$ hours at presentation) to prevent permanent loss of vision.

Hypertensive Retinopathy (HR)

A spectrum of retinal vascular changes pathologically related to microvascular damage from elevated blood pressure, characterized by arteriolar narrowing and vascular leakage.

Macular star

A formation of hard exudates in the macula resulting from chronic retinal oedema in hypertensive retinopathy.

Arteriovenous (AV) nipping

A clinical sign of arteriolosclerosis involving thickening of the vessel wall at the points where arterioles and veins cross.

Copper-wiring

A Grade 3 arteriolosclerosis sign where there is obvious broadening of the arteriolar light reflex.

Silver-wiring

A Grade 4 arteriolosclerosis sign where the arterioles appear like white wires, associated with Grade 3 changes.

Salus sign

The deflection (a change of direction) of a vein at an arteriovenous (AV) crossing.

Bonnet sign

The banking (twisting) of a vein distal to an arteriovenous (AV) crossing.

Gunn sign

The tapering of a vein's width to a small point on both sides of an arteriovenous (AV) crossing.

Retinopathy of Prematurity (ROP)

Disorganised growth of blood vessels with fibrovascular proliferation affecting premature infants of very low birth weight ($\le 1500\,g$) exposed to high oxygen concentrations.

Hyperoxia

High exposure to ambient oxygen concentrations which down-regulates VEGF in premature infants, potentially halting vessel migration and leading to ROP.

ROP Stage 1

The presence of a demarcation line in the retina.

ROP Stage 3

Extraretinal fibrovascular proliferation extending from a ridge into the vitreous.