Corneal swelling (endothelial failure)

What is corneal oedema and endothelial decompensation?

Corneal oedema is a swelling of the cornea caused by an accumulation of fluid. This occurs when the endothelium, the cornea’s innermost layer, ceases to function correctly.

The endothelium acts as a vital pump, constantly removing excess fluid from the cornea to ensure it remains transparent and clear. When these cells are damaged or depleted, fluid builds up, causing the cornea to thicken and clouding your vision.

In advanced cases, small fluid-filled blisters (known as epithelial bullae) can form on the surface of the cornea. If these rupture, they can cause sudden and severe pain. Furthermore, if the swelling is left untreated for a prolonged period, it can lead to permanent corneal scarring and irreversible sight loss.

What are the symptoms?

The symptoms of corneal oedema and endothelial decompensation often fluctuate, appearing most prominent at specific times of the day. Common signs include:

• Blurred or misty vision: This is typically most severe on waking and may improve slightly as the day progresses and the excess fluid evaporates.
• Foggy or hazy vision: You may notice a "fog" over your sight or see halos around bright lights.
• Sensitivity to light (photophobia): Bright environments or sunlight may become increasingly uncomfortable.
• Eye pain or discomfort: In advanced cases, small fluid-filled blisters (bullae) can form on the corneal surface. If these rupture, they can cause a sharp, "foreign body" sensation or intense pain.
• Gradual decline in visual quality: A progressive loss of clarity that can make daily tasks, such as reading or driving, increasingly difficult.

What are the causes?

Several factors can lead to the failure of the endothelial pump, resulting in corneal swelling:

• Fuchs’ endothelial dystrophy is a leading cause. This hereditary condition results in a gradual loss of endothelial cells, progressively weakening the "endothelial pump" over time.‍
• Intraocular Surgery: Procedures performed inside the eye, most commonly cataract or glaucoma surgery, can inadvertently stress or damage the delicate endothelial layer.‍
• Glaucoma: Sustained high intraocular pressure (IOP), often associated with glaucoma, can accelerate the loss of corneal endothelial cells.‍
• Eye Trauma: A direct injury to the eye can cause immediate or delayed damage to the corneal layers.‍
• Ageing: It is natural for the density of endothelial cells to decrease slightly with age; however, in some individuals, this decline leads to a loss of pump efficiency.‍
• Infection and Inflammation: Chronic intraocular inflammation (uveitis) or certain viral infections can compromise the health and function of the endothelial cells.

What are the treatments?

Medical treatments:

• Hypertonic eye drops: Special eye drops help reduce excess fluid in the cornea.
• Therapeutic lenses: In some cases, special contact lenses may be used to relieve pain and protect the surface of the eye.
• Treatment of underlying causes: If inflammation or infection is the cause, it should be treated with appropriate medications (such as antibiotics or anti-inflammatories).

Surgical treatments

When medical management is no longer sufficient, surgical intervention, specifically a corneal transplant, is the standard of care. Modern techniques now allow surgeons to replace only the damaged inner layer rather than the entire cornea.

• DMEK (Descemet Membrane Endothelial Keratoplasty): This advanced technique involves replacing the failing endothelium and its Descemet membrane with an ultra-thin graft (typically 10 to 15 microns). DMEK is currently the gold standard due to its superior visual outcomes and the lowest risk of graft rejection.‍
• DSAEK (Descemet Stripping Automated Endothelial Keratoplasty): A similar endothelial graft option. While the graft is slightly thicker than in DMEK, it remains a highly effective and widely used procedure for restoring corneal clarity.
• DSO (Descemet Stripping Only): Also known as Descemetorhexis without Endothelial Keratoplasty (DWEK), this is a newer, "graft-free" approach. The surgeon removes the central damaged part of the membrane, allowing the patient’s own healthy peripheral cells to migrate inwards. This eliminates the risk of rejection but is typically only suitable for patients with specific types of Fuchs’ dystrophy.‍
• Penetrating Keratoplasty (PKP): This is a full-thickness corneal transplant. It may be necessary in very advanced cases where long-term swelling has caused permanent scarring across all layers of the cornea.

Endothelial transplantation (DMEK/DSAEK), when performed at the appropriate stage, can restore clear vision and significantly improve a patient's quality of life.

It is important to note that prolonged oedema can lead to irreversible corneal scarring. If this occurs, a full-thickness transplant (PKP) becomes the only option to restore sight.

Regular follow-up with an ophthalmologist is essential to monitor the progression of the condition and ensure that surgical intervention is timed correctly for the best possible outcome.