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Almost every tissue in your body is fed by blood vessels — but one part of the eye stays crystal-clear by going without them.
The cornea, the clear dome covering the front of the eye, is one of the few tissues in the human body with no blood vessels running through it. This is essential for vision, since blood vessels would scatter or block incoming light, so instead the cornea gets its oxygen directly from the surrounding air and draws nutrients from tears on its surface and from the fluid inside the eye.
The earlobe and fingertips, by contrast, are well supplied with blood vessels, which is part of why they can bleed noticeably if cut and why fingertips in particular are so sensitive, packed with nerve endings fed by nearby capillaries.
Because it lacks blood vessels, the cornea also has a kind of reduced immune response compared to other tissues, which is one reason corneal transplants have a notably higher success rate than transplants of organs that are richly supplied with blood.
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