Hard exudates, These are well-defined, yellowish-white deposits in the retina, often arranged in rings. They are caused by lipoproteins leaking out of an abnormally permeable blood vessel, which may be visible in the centre of the ring. At the macula they tend to accumulate in a Star
Soft exudates. These look like deposits of cotton wool in the superficial retina. They occur around areas of infarcted retina and may he associated with other features of retinal ischaemia (venous dilatation, haemorrhages and new blood vessels). They are due to swelling of the nerve fibre layer axons (Fig, 7.17).
Colloid bodies. Those may be mistaken for hard exudates. They are small, round yellow deposits in the deepest retinal layer appearing most commonly in the elderly and around the macula (Fig. 7.18).
Other abnormal deposits include foci of active chorioretinal inflammation, metastatic infections (e.g. CMV. miliary tuberculosis) and carcinomas.
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