Vasculopathies

Question 1

Physiology: Retina

Answer 1

1. The fibres of the superficial nerve fibre layer lie parallel to the retinal surface.
2. The elements of the deeper retinal layers lie parallel to the incident light.
3. The photoreceptors are in the wrong position. For the best image they should lie on the retinal
   surface. This anomaly can be explained by the evolution of the retina.
4. The retinal blood vessels supply only the inner retina.
   The choriocapillaris supplies the outer retina, including the photoreceptors.

Question 2

Normal fundoscopy in young person

Answer 2

OPTIC DISC

1. Margin: well defined.
2. Colour of the neuroretinal rim: pink.
3. Cup: pale, round, regular, central, C/D <0.6.

BACKGROUND

1. Glistening with bright colours and regular pigmentation.
2. Neuroretina transparent
3. pigment in the pigment epithelium and the thickness of the choriocapillaris responsible for the colour of the fundus–> varies from dark red to light pink.

RETINAL VESSELS

1. Blood columns: vessel walls are transparent and not visible, but the contained blood columns are clearly visible
2. arterioles are bright red and venules are dark red.
3. Thin light reflex runs along the centre of the blood column.
4. Arteriovenous diameter ratio: 2⁄3 - 3⁄4.
5. Arteriovenous crossings: there is no change in the direction or calibre of either vessel.

CHOROIDAL VESSELS

1. Larger choroidal blood vessels visible through pigment epithelium and choriocapillaris with varying degrees of clarity, depending on amount pigment in the pigment epithelium and the density of the choriocapillaris.
2. They are almost invisible if the choriocapillaris and the pigment epithelium are well developed.
3. The fundus then has a very uniform appearance.
4. Choriocapillaris and pigment epithelium < dense–> the > choroidal blood vessels are prominently visible and this then gives the fundus a striped appearance.

Question 3

Fundus pathology

Answer 3

1. INTRARETINAL HAEMORRHAGES
   - Intraretinal blood tends to track in the same direction as the adjacent retinal elements.
   - Superficial blood tracks along the fibres in the nerve fibre layer which run parallel to the surface.
   - This gives it a flame-shaped or striated appearance.
   - Blood in the deeper layers tracks along the deeper fibres, which run perpendicular to the surface, to give it a dot and blot appearance.
   - It is important to be able to distinguish between superficial and deep haemorrhages as they occur in different diseases.
2. MICROANEURYSMS
   - By convention, small, perfectly round, red spots on the retina, with a diameter smaller than that of the large vein at the disc margin, are referred to as microaneurysms.
   - Any irregularity implies that the spot is a deep haemorrhage and not a microaneurysm.
   - Occasionally a deep haemorrhage will be mistaken for a microaneurysm.
3. HARD EXUDATES
   - Yellowish-white spots with well circumscribed (hard) margins.
   - They represent intraretinal lipid deposition and are a sign of true intraretinal exudation.
   - Lipids which have leaked into the tissues during exudation tend to be less easily reabsorbed because of their large molecular size.
4. COTTON WOOL SPOTS
   - White spots with poorly circumscribed, often striated or fluffy (soft) margins.
   - They represent areas of severe nerve fibre layer ischaemia or infarction.
   - They were previously known as soft exudates, a term that should obviously be avoided.
5. REACTIVE RETINAL PIGMENT EPITHELIAL CHANGE
   - Any damage to the retinal pigment epithelium causes irregular black and white markings in the fundus due to hypertrophy, hyperplasia, atrophy and migration of the pigment epithelium.
   - Pigment epithelial damage is usually associated with damage to adjacent structures such as retina and choriocapillaris.

Question 4

HYPERTENSION RETINOPATHY

Answer 4

1. Diffuse narrowing of the visible blood column in arterioles relative to venules due to generalised vasoconstriction.
2. Areas of focal vasoconstriction produce areas of focal narrowing. Focal narrowing is the most reliable fundoscopic sign of systemic hypertension and usually indicates a diastolic >110mmHg.
3. Severe: Arteriolar obstruction and vessel wall necrosis which manifest as nerve fibre layer haemorrhages, hard exudates and cotton wool spots.
4. Malignant hypertension with diastolic pressures of 130-140mmHg is associated with optic disc swelling.

Question 5

Diabetes Mellitus

Pathology
Consequences of ischaemia
Macular and extra muscular retinal differences 
Classification
Treatment

Answer 5

PATHOLOGY
The basic pathology is a microvasculopathy. It consists of the following:
(a) Capillary outpouching: microaneurysms.
(b) Capillary occlusion → leakage haemorrhage ischaemia

CONSEQUENCES OF ISCHAEMIA
Ischaemia → neovascularisation
- revascularise ischaemic retina.
- ischaemic but viable retina produces vascular endothelial growth factor (VEGF) –> ingrowth of new vessels.

New vessels → leakage haemorrhage
Complications of neovascularisation:
1. Neovascular glaucoma: destruction of the iridocorneal drainage angle.
2. Massive intraretinal exudation.
3. Vitreous haemorrhage → vitreous traction bands → tractional retinal detachment.
The net effect is that neovascularisation does much more harm than good.

MACULAR & EXTRAMACULAR RETINAL DIFFERENCES
structural and functional differences between the macula and the extramacular retina: affect these two areas differently.
As a result we classify the maculopathy and the extramacular retinopathy of diabetes mellitus separately.

CLASSIFICATION

1. Maculopathy
   - Background: As for extramacular retinopathy but with minimal exudation
   - Exudative: Emphasis on oedema and hard exudates
   - Ischaemic: Usually an angiographic diagnosis
2. Extramacular Retinopathy
   - Background: Microaneurysms, Hard exudates, Haemorrhages, Mainly deep: dot and blot, Unusually superficial: flame shaped
   - Preproliferative: Venous beading, kinking and looping, Cotton wool spots, Extensive deep haemorrhages, Vascular Occlusions
   - Proliferative: Neovascularisation

TREATMENT

1. Strict control of blood glucose appears to be beneficial.
2. Argon laser photocoagulation helps in certain types of retinopathy where ischaemia and exudation are a feature.
3. Because treatment is required before the patient becomes symptomatic, it is essential that patients with any form of retinopathy are regularly seen by an ophthalmologist.

Question 6

Central retinal arterial occlusion

Pathophysiology
Cause
Presentation
Treatment

Answer 6

PATHOPHYSIOLOGY

• only one of the branches of the central retinal artery is affected.
• Vision is variable and only that part of the fundus supplied by the occluded branch is affected.
• Neovascularisation does not occur as the infarcted retina is unable to produce a vasoproliferative factor.

Cause

1. Thrombosis and embolism.
2. The effects of an occlusion may be transient or permanent.
3. Carotid atherosclerotic plaques in older patients
4. Cardiac valvar lesions are the main source in younger patients.

SYMPTOMS
1. Sudden, unilateral, severe loss of vision in a comfortable white eye.
2. 1/ more episodes of temporary loss of vision resolves in 24 hr: Amaurosis fugax –> temporary embolic occlusion of the central retinal artery.
SIGNS
1. Visual acuity is usually HM to no PL.
2. Visual field loss.
3. Relative afferent pupil defect.
4. Mild optic disc swelling.
5. Milky white retina especially around the macula –> nerve fibre layer ischaemia and swelling.
6. Cherry red spot–> retina in the centre of the macula is thin, swelling is minimal in this area, and the normal colour of the choriocapillaris can still be seen through the retina. Because of the surrounding pale retina, the centre of the macula appears unusually red.
7. Narrowed arterioles and venules
8. An embolus may be visible in the artery.

MANAGEMENT
1. Digital globe massage: may dislodge the thrombus or embolus.
Retinal nerve fibre layer infarction is relatively complete within 2 hours of onset, and management is ineffective after this.
2. Inhalation of a mixture of 95% O2 to improve O2 delivery to the ischaemic retina.
5% CO2 to effect retinal arterial vasodilation.
3. Systemic vasodilators such as isosorbide dinitrate (Isordil®) sublingually.
5. Acetazolamide (Diamox®) 500mg to < IOP
6. Refer to ophthalmologist –> remove aqueous humour and reduce the IOP.
7. investigate thromboembolic disease:
- giant cell arteritis
- carotid arteriosclerosis
- polycythaemia
- systemic hypertension
- diabetes mellitus.

Question 7

Central retinal venous occlusion

Pathophysiology
Associations
Presentation
Complications
Treatment

Answer 7

PATHOPHYSIOLOGY
Only one branches of the central retinal vein is affected.
Only that part of the fundus drained by the occluded branch is affected.

ASSOCIA TIONS

1. Hypertension and arteriosclerosis
2. Diabetes mellitus
3. Glaucoma

SYMPTOMS
1. Sudden, unilateral loss of vision of very variable degree
2, comfortable white eye.
SIGNS
1. VA and V: normal/severe loss, depending on the degree of obstruction- 6/9 to HM
2. Afferent pupil defect in severe cases.
3. Dilated and tortuous venules.
4. Optic disc swelling.
5. Retinal haemorrhages: Mainly nerve fibre layer (flame shaped) in less severe cases, Mainly deep (dot and blot) in more severe cases.
6. Cotton wool spots in more severe cases.
7. Hard exudates may occur.

COMPLICATION
Neovascularisation.

MANAGEMENT

1. Investigate for treatable causes.
2. Because argon laser photocoagulation is required in more ischaemic cases to prevent neovascularisation, these patients must be followed by an ophthalmologist.
3. Digital globe massage: may dislodge the thrombus or embolus.
   Retinal nerve fibre layer infarction is relatively complete within 2 hours of onset, and management is ineffective after this.
4. Inhalation of a mixture of 95% O2 to improve O2 delivery to the ischaemic retina.
   5% CO2 to effect retinal arterial vasodilation.
5. Systemic vasodilators such as isosorbide dinitrate (Isordil®) sublingually.
6. Acetazolamide (Diamox®) 500mg to < IOP
7. Refer to ophthalmologist –> remove aqueous humour and reduce the IOP.
8. investigate thromboembolic disease:
   - giant cell arteritis
   - carotid arteriosclerosis
   - polycythaemia
   - systemic hypertension
   - diabetes mellitus.

Question 8

Retinopathy of prematurity

Risks factors
Pathogenesis
Treatment

Answer 8

RISK FACTORS

1. Birth weight < 1 500g.
2. Birth weight < 2 000g with an unstable clinical course.
3. Gestational age < 30 weeks.
4. High saturation O2 therapy.

PATHOGENESIS

1. Vascularisation of retina begins @ 16 w gestation: Starts at optic disc–> periphery but is only completed at about 40 w gestation.
2. Babies with risk factors develop neovascularisation at junction of vascularised and nonvascularised retina.
3. Leakage, haemorrhage and fibrosis result, and the contraction of the resultant fibrovascular membrane –> tractional retinal detachment–> end stage: retrolental fibroplasia
4. high saturation O2 therapy: worsen and improve the retinopathy

PRESENTATION:
1. Leukocoria

MANAGEMENT

1. Neonates: dilated examination by an ophthalmologist experienced in dealing with retinopathy of prematurity 4-6 weeks after birth.
2. observation in mild cases
3. cryotherapy
4. laser photocoagulation
5. complex retinal detachment surgery in severe cases.

Question 9

ARTERIOSCLEROSIS RETINOPATHY

Answer 9

1. Diffuse narrowing of visible blood column in arterioles relative to venules due to hypertrophy and fibrosis of the media. The light reflex from the vessel wall becomes more prominent and the blood column becomes paler to produce an appearance of copper wiring and eventually silver wiring when the reflex is relatively broad and the blood column is very pale or invisible.
2. Arteriolovenular (AV) crossing changes become more prominent as the sclerosis progresses. First the venule tapers to disappear behind the arteriole, called AV nipping, and eventually it changes direction at the crossing.