Diabetic Retinopathy

Question 1

How can diabetes affect the eye?

Answer 1

• Infections: due to microvascular changes of diabetes
• Neurological complications: optic neuropathy, 3rd/4th/6th nerve palsy, corneal anaesthesia (neuropathic cornea)
• Lens affected by osmotic fluctuations (cause refractive changes which affect focus and can lead to early onset cataracts)
• Vascular changes (micro + macrovascular changes leading to ischaemia)
• Loss of visual fields caused by ocular ischaemia, secondary glaucoma, micro/macrovascular cerebral disease

Question 2

What are the features of diabetic retinopathy?

Answer 2

• Microaneurysm
• Dot haemorrhage
• Blot haemorrhage
• Exudates
• Cotton wool spots
• Intra-retinal microvascular anomaly (IRMA)
• Ischaemic closure

Question 3

What is the R grade for diabetic retinopathy?

Answer 3

R0 No retinopathy
R1 - Microanuerysms
- Retinal haem < R2 threshold
- Any exudate
- Venous loops
R2 - Any IRMA
- Venous bleeding
- Multiple blot haems > R1 threshold
R3 - proliferative disease, R3a active, R3s stable
- New vessels at disc or anywhere else
- Pre-retinal or vitreous haemorrhage
- Signs of fibrosis or retinal detachment

Question 4

What is the M grade for diabetic retinopathy?

Answer 4

M0 No retinopathy
M1 - Exudate within 1 disc diameter of centre of fovea
- Group of exudate within macula >/= half disc area
- Haemorrhage/microaneurysm within 1DD of centre of fovea if best visual acuity (VA)

Question 5

What stages should be kept under annual review?

Answer 5

R0 + R1

Annual SLB surveillance: ungradable, poor dilation, cataracts

Question 6

What stages need digital surveillance?

Answer 6

R2, R3 stable, M1

Question 7

What stages need routine or urgent referral?

Answer 7

• Hospital Eye Service: R2, R3 active or stable, M1
• Other: glaucoma, vein occlusion, macular degeneration

Question 8

What are the 5 stages of diabetic retinopathy?

Answer 8

1. No retinopathy
2. Mild non-proliferative retinopathy (NPDR) - microaneurysms in earliest stage, dot + blot haemorrhages
3. Moderate NDPR - as above but progressive haemorrhages, exudates
4. Severe/pre-proliferative NPDR - as above but plus multiple blot haemorrhages, venous changes, intra-retinal microvascular anomalies
5. Proliferative - new vessels, fibrous proliferation, vitreous haemorrhage and tractional retinal detachment

Question 9

What are the microvascular changes of diabetic retinopathy?

Answer 9

• BM thickening
• Loss of pericytes
• Loss of endothelial tight junctions
• Breakdown of inner blood retinal barrier
• Leakage and oedema
• Ischaemia
• New vessel formation

Question 10

What are the features of R2?

Answer 10

• Multiple blot haemorrhages
• Flame haemorrhages
• Cotton wool spot
• Exudates

Question 11

What are the features of proliferative advanced R3?

Answer 11

• Severe fibrosis
• Tractional retinal detachment
• Very advanced proliferative retinopathy

Question 12

What are the features of R3s late stage disease (blind)?

Answer 12

• Optic atrophy and fibrosis at optic disc (pale)
• Tented vessel traction
• Laser scars

Question 13

What are the consequences of neovascularisation in advanced DR?

Answer 13

• Vitreous haemorrhage: new vessels bleeding into vitreous
• Retinal detachment: new vessels grow into vitreous and form fibrous bands which suspend the retina (i.e. cause traction on retina, especially pulling on it and causing it to come off)
• Rubeosis: new vessels grow on iris and at drainage angle - increased IOP and progressive glaucoma (eyes can look abnormally red)

Question 14

What are the features of diabetes without retinopathy?

Answer 14

• Hyperglycaemia: damages retinal pericytes (help regulate blood flow through retina)
• Retina looks normal on examination

Question 15

What are the features of non (pre-) proliferative diabetic retinopathy?

Answer 15

• Damaged retinal pericytes causing weakness in capillary walls and increased blood flow
• Weak capillaries increases risks of microaneurysms
• Microaneurysms can be seen as red dots on fundoscopy
• Also, increased vascular permability - capillaries leak, proteins and lipids leak into retina (appears as yellow dots - hard exudates)
• Blood can leak out of capillaries (blot haemorrhages) - hard to distinguish between microaneurysms and blot haemorrhages
• Cotton wool spots (soft exudates) - small, whitish lesions (build-up of dead nerve cells due to nerve ischaemia)
• Macular star-ring of exudates around macula
• Usually asymptomatic

Question 16

What are the features of proliferative diabetic retinopathy?

Answer 16

• Vascular damage causes ischaemia: results in neovascularisation (these blood vessels usually backtrack towards themselves so don’t look like straight lines, are curly)
• Causes blurry vision
• Increases risk of vitreous haemorrhage and retinal detachment (new vessels can grow into vitreous/retina and burst, causing haemorrhage)
• Treatment: laser photocoagulation destroys new blood vessels post-op on fundoscopy - orange-yellow dots