Usually, if you see blood in your eye it's because a tiny blood vessel on the eye has broken open, causing a portion or all of the white of your eye (sclera) to appear bright red.

This painless blood in the eye is called a subconjunctival hemorrhage; and though they look scary, subconjunctival hemorrhages are common and harmless and can be caused by something as simple as a sneeze or cough.

But there's a second type of bleeding in the front of the eye that's much more serious — it's called a hyphema, and it requires immediate attention by your eye doctor.

What Is A Hyphema?

A hyphema is bleeding or a broken blood vessel inside the eye that causes blood to collect in the anterior chamber of the eye — the space between the cornea and the iris that's normally filled with a clear liquid called the aqueous humor.

The severity of a hyphema is graded by how much blood accumulates in the eye:

• Grade 0 (microhyphema): No visible pooling of blood, but red blood cells can be seen within the anterior chamber upon microscopic examination.
• Grade 1: Pooling of blood in less than the lower third of the anterior chamber.
• Grade 2: Blood filling one third to one half of the anterior chamber.
• Grade 3: Blood filling one half to less than all of the anterior chamber.
• Grade 4: Total filling of the anterior chamber with blood. If the blood is bright red, this is called a total hyphema. If it is dark red-black blood, it's sometimes called an "8-ball hyphema."

In general, the higher the grade of hyphema, the greater risk of vision loss and long-term damage to the eye. The dark red or black color of an 8-ball hyphema (the most dangerous type) is associated with decreased circulation of aqueous humor and decreased oxygen in the anterior chamber of the eye.

What Are Other Symptoms Of Hyphema?

In addition to the blood in the eye, the following symptoms usually are associated with hyphema:

• Blurry or distorted vision
• Eye pain
• Light sensitivity (photophobia)
• Headache

Eye pain, sensitivity to light and headache are especially likely to occur if a hyphema is causing increased intraocular pressure (IOP).

What Causes Bleeding In The Eye?

The most common cause of hyphema is trauma to the eye. This is why it is important to see your eye doctor immediately if you sustain an injury that causes a "black eye."

In some cases, a traumatic hyphema also can occur after eye surgery, including cataract surgery. But this is relatively rare.

It's also possible for a hyphema to occur spontaneously, particularly among people who are taking blood thinners (such as warfarin or aspirin) or have a blood clotting disorder (hemophilia). Diabetes also can increase the risk of a spontaneous hyphema, as can tumor growth in the eye (ocular melanoma).

Is A Hyphema Serious? Are There Complications?

Usually, the blood that collects in the anterior chamber of the eye due to a hyphema will be reabsorbed by the body without permanent damage to the eye.

Even if your eye feels fine and your vision seems OK, see an eye doctor immediately if you have eye trauma that could cause a hyphema.

But in some cases, clotting of this blood will clog or damage the structure in the periphery of the anterior chamber that controls the normal outflow of aqueous humor from the eye. This can cause increased eye pressure that can lead to glaucoma and permanent vision loss.

Also, in some cases, rebleeding can occur inside the eye after the initial eye injury that causes a traumatic hyphema. This new bleeding (usually occurring within a few days after the injury) can be more severe and more dangerous than the initial bleeding.

People with sickle cell anemia — a hereditary disease in which red blood cells are distorted into a crescent shape — or those who simply have the genetic trait for this disease have an increased risk of eye damage from a hyphema.

Hyphema Treatment

Depending on the severity of a hyphema and associated risk factors, your eye doctor may recommend a combination of the following precautions and treatments:

• Limited physical activity
• Head elevation (including when sleeping)
• Wearing an eye shield
• Frequent follow-up visits for a few weeks or months
• Pain medicine
• Anti-inflammatory medicine (topical or oral)
• Other medications

In the case of a severe hyphema, surgery may be required.

Do not use over-the-counter pain medications that contain aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) if you have a hyphema, as these medications can increase the risk of rebleeding in the eye.

Even if your eye feels fine and you don't notice vision problems, see an eye doctor immediately if you have eye trauma that could cause a hyphema. Make sure to attend all follow-up visits your doctor recommends.

Also, routine eye exams are very important after having a hyphema, as your risk of elevated eye pressure and glaucoma may be higher even years later.

How Can I Prevent A Hyphema?

The best way to avoid a traumatic hyphema is to wear safety glasses or other protective eyewear whenever you are involved in potentially hazardous activities.

Protective sports glasses should be worn when playing baseball, softball, racquetball, basketball, hockey or other sports that pose a risk of trauma to the eyes.

Also, be aware that sports like boxing significantly increase your risk of a traumatic hyphema. And if you participate in paintball games, wear protective headgear that includes a clear, impact-resistant shield that fully protects your face and eyes.