Corneal edema is swelling of the cornea — the clear, dome-shaped outer surface of the eye that helps you see clearly. It’s caused by fluid buildup in the cornea. When untreated, corneal edema can lead to cloudy vision.

The cornea is made up of layers of tissue that help focus light on the back of the eye to produce clear images. Along the inner surface of the cornea is a layer of cells called the endothelium. Its job is to pump out any fluid that collects inside the eye.

When endothelial cells are damaged, fluid can build up and cause the cornea to swell, clouding vision. Endothelial cells can never regenerate. Once they’re damaged, they’re gone for good.

Diseases that damage endothelial cells and can cause corneal edema include:

  • Fuchs’ endothelial dystrophy (or Fuchs’ dystrophy) is an inherited disease that gradually destroys endothelial cells.
  • Endotheliitis is an immune response that leads to inflammation of the endothelium. It’s caused by the herpes virus.
  • Glaucoma is a disease in which pressure builds up inside the eye. The pressure can build to the point where it damages the optic nerve and, in some cases, lead to corneal edema. This is uncommon, however.
  • Posterior polymorphous corneal dystrophy is a rare, inherited condition of the cornea.
  • Chandler’s syndrome is a rare disorder in which cells of the epithelium multiply too quickly.

Cataract surgery can also damage endothelial cells. Usually the damage isn’t extensive enough to cause problems, but sometimes it can cause corneal edema. Corneal edema that occurs after cataract surgery is called pseudophakic corneal edema or pseudophakic bullous keratopathy. Today, cataract surgery is much less likely to cause corneal edema than it was in the past, because of improvements in lens design.

The use of certain drugs can also increase your risk for corneal edema:

  • benzalkonium chloride, a preservative used in many eye drops and anesthetic drugs
  • chlorhexidine (Betasept, Hibiclens), an antiseptic used to disinfect the skin before surgery
  • amantadine (Gocovri), a drug used to treat viruses and Parkinson’s disease

As the cornea swells and fluid builds up, your vision will become blurred or cloudy. You might notice that your sight is especially hazy when you first wake up in the morning, but it gets better throughout the day.

Other symptoms of corneal edema include:

  • haloes around lights
  • eye pain
  • the feeling that a foreign object is in your eye

If corneal edema is mild, you might not need to treat it. To temporarily relieve swelling in the eye, your eye doctor may recommend concentrated saline (salt-and-water) drops or ointment. For swelling that happens overnight, ask your doctor if it’s safe for you to gently blow air into your eyes with a hair dryer in the morning to evaporate the extra tears. Hold the hair dryer at arm’s length to avoid injuring your eye.

If the swelling gets severe enough to damage your vision, you may need to have surgery to replace either the whole cornea or just the endothelial layer with healthy corneal tissue from a donor. Procedures used to treat corneal edema include:

Penetrating keratoplasty (PK or PKP)

The surgeon removes all the layers of your cornea and replaces them with healthy tissue from a donor. The new corneal tissue is held in place with sutures.

Because the graft may be irregularly shaped, after this surgery you might need to wear corrective lenses to see clearly.

Risks from this surgery include damage to the lens of the eye, bleeding, glaucoma, or rejection of the graft.

Descemet’s stripping endothelial keratoplasty (DSEK)

This procedure replaces only the damaged endothelial layer of your cornea, leaving the rest intact. Both the procedure and the recovery are faster than with PK.

Your recovery time depends on the severity of your corneal edema, and how it’s treated. Mild corneal edema might not cause any symptoms or require treatment.

If you have surgery to replace your entire cornea, it could take a year or longer to get your vision back fully. Because the new cornea could be irregularly shaped, you may need to wear glasses to achieve clear vision.

Healing is much faster after a DSEK procedure, which removes only part of your cornea.

The outlook depends on the cause of corneal edema. Mild edema might progress very slowly, so you may not notice any symptoms for a period of years — or even decades. For more severe edema, having surgery and wearing glasses or contact lenses can restore much of the vision you lost.