Superficial Retinal Hemorrhages
Superficial retinal hemorrhages are small, linear, flame-shaped, red streaks in the fundi. They are shaped by the superficial bundles of nerve fibers that radiate from the optic disc in the pattern illustrated (O = optic disc; F = fovea). Sometimes the hemorrhages occur in clusters and then simulate a larger hemorrhage, but the linear streaking at the edges shows their true nature. Superficial hemorrhages are seen in severe hypertension, papilledema, and occlusion of the retinal vein, among other conditions.
An occasional superficial hemorrhage has a white center consisting of fibrin. White-centered retinal hemorrhages have many causes.
Deep retinal hemorrhages are small, rounded, slightly irregular red spots that are sometimes called dot or blot hemorrhages. They occur in a deeper layer of the retina than flame-shaped hemorrhages. Diabetes mellitus is a common cause.
A preretinal (subhyaloid) hemorrhage develops when blood escapes into the potential space between retina and vitreous. This hemorrhage is typically larger than retinal hemorrhages. Because it is anterior to the retina, it obscures any underlying retinal vessels. In an erect patient, red cells settle, creating a horizontal line of demarcation between plasma above and cells below. Causes include a sudden increase in intracranial pressure.
Microaneurysms are tiny, round, red spots seen commonly but not exclusively in and around the macular area. They are minute dilatations of very small retinal vessels, but the vascular connections are too small to be seen ophthalmoscopically. Microaneurysms are characteristic of diabetic retinopathy but not specific to it.
Neovascularization refers to the formation of new blood vessels. They are more numerous, more tortuous, and narrower than other blood vessels in the area and form disorderly looking red arcades. A common cause is the late, proliferative stage of diabetic retinopathy. The vessels may grow into the vitreous, where retinal detachment or hemorrhage may cause loss of vision.
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