Blood vessels in the eye provide oxygen and nutrients to the cells. When the eyes become red, it is commonly due to tiny blood vessels beneath the eyes bursting. Diseases such as diabetic retinopathy and macular degeneration cause the proliferation of new vessels in the retina that can leak and cause vision loss. The cornea normally does not contain blood vessels. However, abnormal blood vessels can grow in the cornea in response to hypoxia.
Blood Vessels Beneath Conjunctiva
The conjunctiva is a thin membrane that covers the back of the eyelid and the white part of the eye called the “sclera”—extending to the point where the sclera and cornea meet. According to Marjorie Ward, contributor to the book “Foundations of Low Vision,” the conjunctiva serves as a transparent barrier between the eye’s orbit—not including the cornea—and everything in front of it.
Gary Cassel, M.D., Michael Billig, O.D., and Harry Randall, M.D., authors of “The Eye Book,” report that blood vessels under the conjunctiva can break for no apparent reason or as a result of an injury, making the eye appear frighteningly red. If this “subconjunctival hemorrhage” occurs frequently, it may be a signal of a health problem, but it is typically not a cause for concern.
Blood Vessels in Retina
According to Cassel, Billig and Randall, blood reaches the eye through the aorta and carotid arteries, which transport blood up through the neck and into a smaller vessel called the ophthalmic artery. The most critical vessels that carry blood to and from the retina are the central retinal artery, which supplies oxygen-rich blood to the sensory part of the retina, and the central retinal vein, which takes blood back toward the heart.
The retina has the job of converting light into impulses, sending them to the brain to be interpreted as images. Any blockages of the blood supply to the retina due to a stroke or other disease can cause vision loss. In addition, blockages can cause swelling and a backup of blood that can cause macular edema and hemorrhage.
Patients with a disease such as diabetic retinopathy often develop new fragile blood vessels in the retina. According to the University of Michigan Kellogg Eye Center, the weakened vessels can break, bleed and cause the growth of scar tissue, which can pull the retina away from the back of the eye. An untreated detached retina causes blindness.
Abnormal Blood Vessels in the Cornea
The cornea is a transparent protective layer in the eye that bends light to converge at a point of focus on the retina. Cassel, Billig and Randall describe the cornea as rich in sensory nerve fibers, which is why it is so sensitive to pain. According to the National Eye Institute, the cornea helps to shield the eye from germs and dust and is involved in producing cleansing tears.
The cornea normally does not have any blood vessels. However, abnormal blood vessels may grow in the cornea, especially along the edges, as a result of hypoxia caused by contact lenses that reduce the cornea’s ability to obtain oxygen. The authors on the website Contact-Lens-Problems.com report that this problem is commonly associated with the use of soft contact lenses that do not have high permeability.
Blood Vessels in the Iris
The iris is the part of the eye that gives eye color, with the pupil in the center. The iris has muscles that control the size of the pupil—contracting in a bright room and dilating in a darkened environment. According to Cassel, Billig and Randall, the iris is surrounded by the “ciliary body” that tethers the eye's lens in place and is connected in back with the choroid—a nourishing layer of blood vessels between the sclera and retina. The iris, choroid and ciliary body all work together to nourish the eye.
References
- National Eye Institute: Facts About Age-Related Macular Degeneration
- The University of Michigan Kellogg Eye Center: Diabetic Retinopathy
- Contact Lens Problems: Blood Vessel Growth
- Med Rounds: Iris
- National Eye Institute: Facts About the Cornea and Corneal Disease
