Eye Complications in Diabetes

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Main cause of blindness in adults in developed countries. Almost all those with diabetes will eventually develop some form of retinopathy (especially those with Type 1). Retinopathy is asymmetric until well developed. Presence in both type 1 and 2 are closely correlated to the duration of diabetes and the quality of glycaemic control. Eventually develops in most Type 1 patients due to duration of diabetes, but may not be more than ‘background’ retinopathy. Up to 20% of those with Type 2 have signs of retinopathy at time of diagnosis.

Two basic pathophysiological mechanisms – increased capillary permeability and closure of retinal capillaries  vascular leakage  retinal oedema and accumulation of lipids  seen as hard exudate in the retina and retinal ischaemia.

Clinical features:
Symptoms are uncommon until well established – can include a myopia, visual disturbances, ‘floaters’
Presence is best detected with ophthalmoscope through dilated pupils
Earliest signs are microaneurysms (small discrete dark red spots near retinal vessels); haemorrhages; hard exudate (appear as spots in perimacular area); soft exudate (appear as ‘cotton wool’ spots; retinal infarcts) venous dilation; new vessel formation occurs as growth factors released.
A transient worsening of retinopathy often follows improvements in glucose control.

Classification/types:
• background retinopathy – have microaneurysms, intraretinal haemorrhages, cotton wool spots and hard exudate
• pre-proliferative retinopathy – have venous loops, retinal infarcts; multiple haemorrhages
• proliferative retinopathy – new vessel formation
• advanced diabetic eye disease – retinal detachment, new vessels in iris
• maculopathy – exudate, oedema, ischaemia

Factors associated with worsening diabetic retinopathy:
Later age of onset of diabetes; poor control of diabetes; longer duration of diabetes; associated hypertension or nephropathy; insulin treatment; pregnancy; smoking.

Management:
DCCT showed intensive treatment for tight control of blood glucose levels reduces risk by 76%. UKPDS showed a 25% overall reduction in microvascular complications in the intensive group versus the conventional group. Both studies show that good glycaemic control does not prevent retinopathy, but it does reduce the risk.
Those with background retinopathy should be regularly reviewed for progression  referral to ophthalmologist
Laser photocoagulation is very helpful to destroy areas of retinal ischaemia, seal leaking microaneurysms and obliterate new vessels  importance of regular screening for those at risk.
Several cost effectiveness analyses have shown that screening for diabetic retinopathy shows the screening saves vision for a relatively low cost .
Will need other supports for visual impairment (eg braille instruction, large print books, guide dogs)

Other eye conditions in diabetes:
cataract – develop earlier in those with diabetes; higher risk if also taking corticosteroids
glaucoma – more common in those with diabetes;
a transient visual disturbance is also common due to osmotic changes
anterior ischaemic optic neuropathy
corneal dystrophy

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