Diabetic Eyes

Question 1

Why do we screen for diabetic retinopathy?

Answer 1

Diabetic retinopathy is the leading cause of blindness in those aged 20-65 in the UK. Mostly this occurs in advanced diabetes and not at presentation but 30% will have signs at presentation. Little can be done in advanced disease hence why screening takes place.

Question 2

How does diabetes cause retinopathy?

Answer 2

Hyperglycaemia increases retinal blood flow and causes abnormal metabolism in the retinal vessel walls. This damages the endothelial cells and the pericytes. Overall this causes increase permeability and pericytes dysfunction causes microaneurysm formation. Neovascularisation or rubeosis occurs due to growth factor production form retinal ischaemia.

Question 3

What changes are seen in diabetic retinopathy?

Answer 3

• Ocular ischaemia causes rubeosis which can lead to glaucoma if drainage is blocked. The new vessels can also bleed and increases the risk of retinal detachment. This can be seen as haemorrhages or as cotton wool spots (ischaemic nerve fibres).
• Vascular leakage due to microaneurysms
• Macular oedema and hard fatty exudates due to damage blood cells
• Acceleration of cataract formation
• Can get CNIII or CNVI palsies as well as Horner’s

Question 4

Describe non-proliferative retinopathy?

Answer 4

Non-proliferative retinopathy - rated as mild, moderate or severe based on the level of ischaemia. Signs include: microaneurysms (dots), haemorrhages (flame shaped or blots), hard exudates (yellow patches), engorged tortuous veins, cotton wool spots and large blot haemorrhages (the last 3 are signs of severe disease). This can progress to proliferative diabetic retinopathy.

Question 5

What are the 3 severities of non-proliferative retinopathy?

Answer 5

• Mild – one or more microaneurysm
• Moderate – microaneurysms, blot haemorrhages, hard exudates, cotton wool spots and venous beading/looping
• Severe – microaneurysms and blot haemorrhages in 4 quadrants, venous beading in at least 2 quadrants and intraretinal microvascular abnormalities in at least 1 quadrant

Question 6

What is proliferative retinopathy?

Answer 6

Proliferative diabetic retinopathy – formation of fine new blood vessels on the optic disc, retina that lead to vitreous haemorrhage. Leakage of vessels near the macula cause maculopathy leading to oedema and threatens visual acuity.

Question 7

How should suspected diabetic retinopathy be investigated?

Answer 7

Dilated fundus photography
OCT – macula oedema seen towards the top layer
Fluorescein angiography taken at two stages after injection
B scan ultrasonography

Question 8

How is diabetic retinopathy screened for?

Answer 8

All diabetics should have their eyes screened at diagnosis but also annually. Screening involves dilated fundus photography.

Question 9

When should a referral be made for diabetic retinopathy?

Answer 9

1. Maculopathy – retinal thickening within one disc diameter of the centre of the fovea, exudate within the macula or microaneurysm or haemorrhage within one disc diameter of the centre of the fovea or if acuity is <6/12. Any pathology on the macula is potentially serious, much more common in type II DM.
2. Signs of pre proliferative retinopathy such as venous bleeding, venous loops or round or blot haemorrhages – routine referral
3. Proliferative retinopathy is seen – fast track referral

Question 10

How is diabetic retinopathy managed?

Answer 10

BP < 140/80 or 130/80 if evidence of end organ damage
Maculopathy and proliferative retinopathy are both treated with photocoagulation
Intravitreal triamcinolone (steroid) and anti VEGF injection are used alongside laser to treat macula oedema.

Question 11

How does hypertension cause retinopathy?

Answer 11

Increased BP damages retinal vessels. The hardened arteries are shiny and called silver wiring. These narrowed hardened vessels may become blocked causing localised infarction, seen as cotton wool spots. These can leak causing hard exudates and macular oedema. Papilloedema and flame haemorrhages are a sign of severe disease and require urgent treatment.

Question 12

What classification system is used to differentiate the severity of hypertensive damage?

Answer 12

Hypertensive Retinopathy is classified by the Keith-Wagner Classification system.

I Arteriolar narrowing and tortuosity
Increased light reflex - silver wiring

II Arteriovenous nipping

III Cotton-wool exudates
Flame and blot haemorrhages

IV Papilloedema