There are usually no ophthalmic symptoms initially, but inspection of the fundi of most diabetics who have had the disease for ten years or more reveals, at first, a few microaneurysms. They are often on the temporal side of the macula but often scattered over the posterior pole of the fundus (Figure 21.2). These might come and go over months and the overall picture could be unchanged for several years. The vision is not affected unless the micro-aneurysms are clustered round the macular region and leak fluid, resulting in macular oedema. Exudates are also seen and these tend to form rings around areas of diseased vessels, although only one part of the ring might be present at any given point. These are yellowish-white deposits with well-defined edges, which are the result of precipitation of leaked lipo-proteins from diseased blood vessels. Capillary dilatation is a more subtle sign of diabetic retinopathy. Haemorrhages, which can be small ("dot") or large blot, result from the venous end of capillaries and are in the deep retina. Flame-shaped haemorrhages can also occur in the nerve fibre layer. "Cotton-wool" spots represent axoplasmic accumulation adjacent to micro-infarction of the retinal nerve fibre layer. They
are greyish-white with poorly defined fluffy edges. Histological examination of diseased retina has shown areas of capillary closure and capillary microaneurysms. The vessel walls have thickened basement membranes and loss of mural cells (pericytes) (Figure 21.3).
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Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...