Page 460 - Medicine and Surgery

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456 Chapter 11: Endocrine system

Incidence vision for months or years. Scar formation leads to
Leading cause of blindness under the age of 65 in the atraction retinal detachment. New vessels forming at
developed world. After 20 years of diabetes almost all pa- theirisareaccompaniedbyobstructionatthedrainage
tients have some retinopathy. Around 40% of type 1 and angle causing a neovascular or thrombotic glaucoma
20% of type 2 diabetics have proliferative retinopathy. (a type of secondary closed angle glaucoma).
Aetiology Complications
Control of blood sugars and concomitant hypertension Proliferative retinopathy may cause sudden loss of vi-
has been shown to reduce risk of retinopathy and other sion from extensive haemorrhage or retinal detachment.
microvascular complications. Thrombotic glaucoma may also occur.
Investigations
Pathophysiology
Screening is by fundoscopic or retinal camera examina-
There is a thickening of the capillary basement mem-
tion. Patients require dilation of the pupils. Fluorescein
braneandhyalinearteriosclerosis.Microaneurysms(dot
angiography can be used to show very early disease. Acu-
haemorrhages) occur in some vessels while others be-
ity testing should be performed to detect early macular
come occluded. The weakening of the vessel walls leads
disease.
to blot haemorrhages, and transudates of fluid and lipid
(hard exudates). The obliteration of capillaries causes Management
retinalischaemia(cottonwoolspots)whichinturnstim- No specific treatment is required for background
ulates the formation of new vessels at the surface of the retinopathy except to maximise diabetic control and
retina and iris. manage any coexisting hypertension.
Maculopathy is treated by laser to the centre of a hard

Clinical features exudate.
All patients with diabetes should be screened regularly Proliferative retinopathy is treated by panretinal pho-
for diabetic retinopathy. tocoagulation (PRP), widespread pinpoint laser treat-
Background diabetic retinopathy is the earliest sign ment to the periphery of the retina, destroying the is-

of diabetic retinopathy. Initially there are microa- chaemic retina. There is then reduction in the growth
neurysms later accompanied by blot haemorrhages factors which promote neovascularisation and hence
and scattered hard exudates. Vision is generally unaf- regression of new vessels. Laser treatment also helps
fected. prevent neovascular glaucoma.
Diabetic maculopathy causes gradual loss of vision Surgery may be required to remove vitreous haemor-

due to: rhage and fibrous tissue or to repair a detached or torn
i. Capillary leakage causing macular oedema retina.
ii. Lipid deposition
iii. Extensive obliteration of macular capillaries Prognosis
Pre-proliferative retinopathy is seen most commonly Prevention is the best management, by regular screening

in young patients on insulin for about 10 years. Reti- and good control of blood sugar.
nal ischaemia is seen as ‘soft exudates’ or cotton wool
spots. Fifty per cent of patients with pre-proliferative Diabetic nephropathy
changes develop proliferative retinopathy within a
year. Definition
Proliferative retinopathy: New vessels develop most Diabetic nephropathy is a microvascular disease of type

commonlyattheopticdisconthevenoussideadjacent 1 and 2 diabetes.
to the temporal vessels. They grow into the vitreous
and round to the front of the eye when they are visible Incidence
on the iris. These vessels may bleed either as vitreous Patient individual risk is falling however due to increas-
(blue-greyopacity)orpre-retinalhaemorrhages(usu- ing rates of diabetes the overall prevalence of diabetic
ally flat upper surface), which may cause obscuring of nephropathy is rising.