When I get tired it looks like the blood vessels in my eye swell up, why? Are they in the sclera?
No those are in the conjunctiva. When you get tired you may tend to blink less and your eyes begin to get dry(especially if you are a contact lens wearer)
Wow is that why! No way!
Do you find that you rub your eyes when you are tired? Irritation such as this can also cause swelling of the vessels in the conjunctiva.
Once your eyes have begun to dry out the blink rate increases to compensate. Since the cornea has no blood vessels it must get its O2 and nutrients from the tears and aqueous.
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