Is the sclera avascular (without blood vessels)?
JAN 31, 2019
Is the sclera avascular (without veins)?
There are three layers in the sclera (white part of the eye) and each of them contain blood vessels. They are usually not visible to the external observer except in certain inflammatory conditions. Blood vessels in the outermost layer, the episclera, dilate (widen) and become visible in a condition called episcleritis. The blood vessels in the middle layer of the sclera, called the stroma, are much sparser, but they also can be seen in someone with scleritis. The innermost portion of the sclera (called the lamina fusca) also contain blood vessels, but they are not visible.
In addition, there are a number of blood vessels passing through the sclera, including those that supply the conjunctiva (thin, transparent membrane covering the sclera), iris (colored part of eye), choroid (layer of tissue between the sclera and the retina), optic nerve (back of the eye that connects to the brain), extraocular muscles (muscles that control eye movement) and the sclera itself.