Blood in the Cornea: On Hematomas, Hemorrhages and Staining

The eye is a sensitive area, and if blood appears there suddenly after an eye injury or unexpectedly, well … it can understandably lead to a lot of panic and a scramble to get to an ophthalmologist for an eye exam to see what‘s up. 

In this article, we are going to cover some common causes of blood in the front part of the eye and especially the cornea, from the more common ones like a subconjunctival hemorrhage, to rare ones like the different types of corneal hematomas, corneal hemorrhages and corneal blood staining. So, if blood in the eye has you or someone you know looking like something straight out of a horror movie, read on to make more sense out of your ophthalmologist’s diagnosis. 

And although blood in the eye doesn‘t necessarily mean something serious is wrong, if you haven‘t consulted with a doctor, it’s best to do so immediately and get under that slit lamp to make sure.

Hematoma vs. Hemorrhage

Whenever you hear about blood anywhere on the body, the first words you are likely to hear are hemorrhage and hematoma. In ophthalmology and medicine in general, when you see a word that contains hem-, you should know we are talking blood. But what‘s the difference between these two conditions, if there is one?

Some doctors will use these terms interchangeably with the layman, or even by accident, but there is a difference. It’s best to think of a hemorrhage as an “action” word. When a blood vessel ruptures and blood is actively flowing, this event is called a hemorrhage. Blood vessels are more or less the pipes all over your body that carry blood around, and they come in many different shapes and sizes from big arteries to tiny little veins and capillaries. Technically everything from bleeding from a minor cut to massive blood loss from a severe injury is called a hemorrhage, though the term is more often than not reserved for more serious problems.

If a hemorrhage is the action of blood loss, then a hematoma is the “thing” that is the result of this blood loss. When blood comes out of a blood vessel from a hemorrhage, it inevitably leaks into the surrounding tissues, and when this forms a sticky clot, it has turned into a hematoma. Therefore it is best to think of the hemorrhage as the action of blood flowing, and a hematoma as what happens when it pools in the tissues.

Got that? Great! Now that we’ve got this basic difference down let’s take a look at what could be causing that blood in your eye.

Subconjunctival Hemorrhage

The most common, and perhaps most alarming-looking, of the causes of blood in the cornea is a subconjunctival hemorrhage. This is not actually blood in the cornea per se, but it is so common and looks so much like blood has entered the cornea that it is worth mentioning here at the beginning. The conjunctiva is the part of the eye covering the “white” of the eye, or the sclera, and subconjunctival hemorrhage occurs when a blood vessel underneath the conjunctiva breaks. Though your conjunctiva is normally clear, you can actually see these blood vessels when you have dry eye or allergies. And when one of these little guys ruptures and stains a large part of the white red, you’ve got yourself a subconjunctival hemorrhage.

Sounds awful, right? Great news, it’s not awful at all, and is just a case of something that looks far worse than it is. The cause of a subconjunctival hemorrhage is almost always benign, and can include things like sneezing or coughing, abrasion from rubbing your eyes too hard, vomiting, or just in general straining your eyes. It’s pretty clear that you will want to (and should) go get this checked out by your healthcare provider, but don’t fear; it’s usually not an ocular catastrophe and will clear up eventually.

Corneal Hematoma

The cornea is the outermost, clear part of the eye that covers the non-white part of your eye, and lays on top of the anterior chamber. Together with the conjunctiva, which we talked about in the previous section, it serves as the outer layer of your eye. This, combined with the fact that it is one of the most commonly operated-on parts of the eye, makes the cornea particularly prone to injury. When you have a hematoma that forms in the cornea, it is most often called an intracorneal hematoma, or just a hematoma.

The good news is that there are no blood vessels in the cornea itself normally, and so intracorneal hematomas are relatively rare; the cornea is simply too far away from most blood vessels for blood for a hemorrhage to leak into it.

The cornea is like a transparent sandwich, with the “bread” being the Descemet’s membrane and the endothelium on one side and the epithelium on the other side. The stroma or stromal layer would be the “meat” of the sandwich, and this is where an intracorneal hematoma is likely to be.

Corneal hematomas are pretty rare, and can have several causes. The first is an intracorneal hematoma after canaloplasty. Canaloplasty is a type of surgical management for glaucoma, and especially open-angle glaucoma where intraocular pressure (measured in mmHg) is lowered by a surgeon. For further reading, you can access the full text of a case report involving a patient who underwent a canaloplasty and cataract surgery here.

Corneal hematomas usually have to be removed surgically to maintain eye health. Corneal hematomas, especially in combination with epithelial defects, can cause some serious damage. Like any other tissue, your cornea needs food and the hematoma can put a stopper on that, leading to major issues like degeneration of the epithelium and loss in visual acuity. Thus, corneal hematomas often require surgery or other potentially invasive treatments to remove before they can wreak serious havoc on your ocular systems.

Corneal Hemorrhage

Next up is a corneal hemorrhage, also called an intracorneal hemorrhage. If you’re still with us here, you might be thinking to yourself, “hey, how can you have a hemorrhage in the cornea if there are no blood vessels there?” You may recall from the previous section that the cornea actually doesn’t have any blood vessels inside, and without them, how can you have a hemorrhage?

The answer to that question is that certain things can actually make blood vessels in the cornea, called vascularization in fancy doctor talk. As the cornea is supposed to be transparent so that light can enter unobstructed, this is unsurprisingly not a good thing. Things like trauma, corneal ulcers, keratitis, and even wearing contact lenses for prolonged periods of time can lead to veins forming in the cornea, among other things. In any case, corneal hemorrhages need immediate treatment, as pretty much anything that gets stuck inside the cornea can lead to some serious issues. Treatment options vary depending on how deep the hemorrhage is, but getting to the doctor is the key.

Corneal Blood Staining

The last condition which warrants discussion in this overview of conditions that can put blood in your cornea is corneal blood staining. Corneal blood staining is as serious as it is rare, and gives the cornea a brownish-red, opaque look as blood stains the cornea from below. This is a pretty rare condition, caused by prolonged hyphema, which is a type of hemorrhage elsewhere in the eye usually caused by trauma. When this hyphema is combined with raised intraocular pressure, blood breaks through the endothelium at the bottom of the cornea and begins staining the stromal tissue (think: meat of the sandwich as explained above). This condition is quite serious, as it can take months to years to clear up and affects your visual acuity. So, if your eye has undergone trauma and there is hyphema, just make sure that you get in to see the doctor so he or she can estimate the risk to your cornea for complications like blood staining.

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