Diabetic Retinopathy Flashcards
Diabetic retinopathy is the most common cause of blindness in what age group?
Adults aged 35-65
What percentage have ocular problems when diabetes presents?
30% , but the majority remain asymptomatic until advance disease takes hold (at which point little can be done)
Describe the pathogenesis
Microangiopathy in capillaries causes:
1) vascular occlusion leading to ischaemia +/- new vessel formation (which bleed). Ischaemia causes cotton wool spots
2) vascular leakage as pericytes are lost - capillaries bulge (micro aneurysms) and there is oedema and hard exudates. Rupture of micro aneurysms can cause flame shaped haemorrhages or blot haemorrhages
What are cotton wool spots?
Ischaemic nerve fibres
What is the impact of hyperglycaemia?
Increased retinal blood flow and abnormal metabolism in retinal vessel walls - damage to endothelial cells and pericytes
What does endothelial dysfunction lead to?
Increased vascular permeability - causes the characteristic exudates seen on fundoscopy
What does pericyte dysfunction predispose?
Micro aneurysms
What is neovasculisation thought to be caused by?
Production of growth factors in response to ischaemia
What are hard exudates comprised of?
Lipoprotein and lipid filled macrophages. It has leaked from abnormal retinal capillaries, so often associated retinal oedema
What are the two types of diabetic retinopathy?
Non-proliferative diabetic retinopathy
Proliferative diabetic retinopathy
How is NPDR rated?
Mild
Moderate
Severe
Depending on degree of ischaemia
Describe mild NPDR
1 or more micro aneurysms (small red dots often in clusters), do not affect vision
Describe moderate NPDR
Micro aneurysms
Blot haemorrhages
Hard exudates
Cotton wool spots, venous beading/ looping and intraretinal microvascular abnormalities less severe than in severe NPDR
Describe severe NPDR
Blot haemorrhages and micro aneurysms in 4 quadrants
Venous bleeding in at least 2 quadrants
Itraretinal microvascular abnormalities at least 1 quadrant
Describe proliferative diabetic retinopathy
Fine new vessels appear on optic disc, retina and can cause vitreous haemorrhage
What is maculopathy?
When macula is affected by retinopathy
Leakage of vessels close to macula can cause macula oedema - can significantly threaten vision
Who should be referred urgently for assessment and treatment?
Those with:
Maculopathy
Severe NPDR
PDR
How can DM cause glaucoma?
DM causes ocular ischaemia, which can cause new blood vessels to form on the iris - these can block the drainage of aqueous fluid
The formation of age related cataracts is accelerated in DM. True or false?
True
How often should those with DM type 1 and 2 have their eyes screened?
At time of diagnosis and then at least annually
Screening is done by…
Dilated fundus photography - referrals then made accordingly
Lesions mostly at posterior pole and can be seen by ophthalmoscope
Proliferative retinopathy heightens the risk of…
Retinal detachment
Fibrosis and connective tissue develops - asserts traction
What do micro aneurysms look like?
Small red dots often in clusters
What are the earliest clinically visible changes of diabetic retinopathy?
Micro aneurysms
Do micro aneurysms affect vision?
No
Intraretinal haemorrhages may be dot, blot or flame depending on…
Their depth within the retina
The capillary layer in the posterior retina has 2 layers - superficial in nerve fibre layer and deeper on within nuclear layer. Haemorrhages within nerve fibre layer = flame shaped, inner layer haemorrhages = dot or blot
The hard exudates (intra retinal deposits) can vary from small specks to large patches and may evolve into rings known as…
Circinates
Where are the hard exudates principally found?
Macular region and as the extend into fovea, vision can be severely compromised
What do cotton wool spots look like?
Greyish white patches in the nerve fibre layer which has fluffy edges.
What are intraretinal microvascular abnormalities?
Areas of capillary dilatation and intraretinal new vessel formation. Arise within ischaemic retina
When neovascularisation occurs, where are the new vessels usually found?
Initially seen as fine tufts on surface of the disc
Large veins
What is a sub-hyaloid haemorrhage?
New vessels form abnormal adhesions with vitreous. Where there is areas of detachment of vitreous, blood can accumulate between retina and vitreous = sub hyaloid haemorrhage
What is used to treat maculopathy and proliferative retinopathy?
Photocoagulation
Trans pupillary laser applied so as to produce a retinal burn - used to treat the new blood vessels
It does not improve vision, it is intended to prevent blindness
What can accelerate retinopathy?
Pregnancy Hypertension Renal disease Dyslipidaemia Smoking Anaemia
What is used to treat macula oedema?
Intravitreal triamcinolone and anti VEGF drugs
Focal laser treatment to seal any leaking micro aneurysms
What can reduce the risk of visual deterioration in patients with diabetic macula oedema by at least 50% ?
Grid laser therapy
What are some side effects of laser treatment?
Loss of peripheral vision, colour vision, night vision
How can diabetic retinopathy be prevented?
Keep blood sugar levels as close to normal as possible
Control BP <140/80 or < 130/80 if end organ damage
Lower cholesterol
What examinations can be done?
Slit lamp/ ophthalmoscope
Fluorescein angiography to assess damage
Optic coherence tomography to assess if any macula oedema
What is fluorescein angiography?
A test to examine the back of the eye - see if there are any problems with the vessels there.
Vein injected with the yellow sodium fluorescein dye - travels round body. Retina illuminated with blue light.
Angiogram obtained by photographing the green light that is emitted.
What symptoms occur with diabetic retinopathy?
Early stages usually no symptoms
Some people may notice trouble reading or seeing objects far away
In later stages - vessels start to bleed into vitreous gel - dark, floating spots or streaks that look like cobwebs
If macular oedema present: blurry vision due to extra fluid
Why can diabetic retinopathy cause retinal detachment?
It can cause scars to form at back of eye
These scars can pull the retina away from the back of the eye
