Pseudophakic Bullous Keratopathy

Cataract surgery is one of the most common and successful surgical procedures performed worldwide, restoring clear vision for millions. However, in a small percentage of cases a complication known as pseudophakic bullous keratopathy (PBK) can arise, leading to persistent corneal swelling and blurred vision after surgery.

The term pseudophakic refers to an eye that has an artificial intraocular lens (IOL) implanted, which is standard practice in modern cataract surgery. Bullous keratopathy describes a cornea that has become swollen and may develop blisters (bullae) on its surface, due to failure of its innermost layer — the endothelium.

The root of the problem: endothelial cell damage

The cornea’s clarity is critically dependent on its endothelial cells. This single layer of cells on the back surface of the cornea functions like a pump, constantly removing fluid to keep the cornea thin and transparent. Humans are born with a finite number of these cells, and they do not regenerate effectively once damaged or lost.

Any intraocular surgery, including cataract surgery, inevitably causes some stress and a degree of loss to these delicate cells. In most patients the remaining cells are more than sufficient to maintain clarity. PBK can develop when:

• Pre-existing endothelial weakness. The patient already had a low endothelial cell count or an underlying condition such as early Fuchs’ dystrophy before cataract surgery. In such cases even routine surgery may push the endothelium beyond its capacity to compensate.
• Surgical complexity or complications. A particularly challenging cataract operation — a very dense cataract, prolonged surgical time, or intraoperative complications such as vitreous loss or instrument damage — can cause greater-than-average endothelial cell loss.
• Post-operative inflammation. Significant or prolonged inflammation after surgery can also damage endothelial cells.

When endothelial cell density drops below a critical threshold, the pump mechanism fails, fluid accumulates within the cornea, and transparency is lost.

Symptoms

Symptoms can appear weeks, months or even years after cataract surgery. Common signs include:

• Persistently blurred or hazy vision that does not clear after the initial post-operative period
• Fluctuating vision, often worse in the morning
• Glare and sensitivity to light
• Haloes around lights
• In more advanced cases, eye pain, a gritty sensation or excessive tearing, especially if surface blisters form and rupture

Diagnosis

Diagnosis is typically made on the basis of:

• Patient history — a key factor is previous cataract surgery.
• Slit-lamp examination — allows the ophthalmologist to observe corneal oedema and potentially bullae. The presence of an IOL confirms the pseudophakic status. Signs of pre-existing conditions such as guttae may also be noted.
• Pachymetry — measures corneal thickness; increased thickness indicates oedema.
• Specular microscopy — visualises and counts the endothelial cells, assessing their density and health. A significantly low cell count is a hallmark of PBK.

Treatment

Treatment aims to reduce corneal swelling and improve vision.

Medical management — often temporary or palliative

• Hypertonic saline solutions. Drops or ointments (for example 5% sodium chloride) draw fluid out of the cornea, providing temporary relief from swelling and improving vision, especially for mild oedema.
• Bandage contact lenses. If painful bullae are present, a soft bandage lens protects the cornea and relieves discomfort.
• Intraocular pressure–lowering medication. Reducing eye pressure can sometimes lessen corneal oedema.

Surgical management — definitive treatment

For persistent and visually significant PBK, corneal transplantation is usually necessary.

• DMEK is often the preferred procedure. It selectively replaces only the damaged Descemet’s membrane and endothelium with healthy donor tissue, offering rapid visual recovery and excellent outcomes for PBK.
• DSAEK/DSEK is another effective endothelial keratoplasty technique that replaces the posterior layers of the cornea.
• Penetrating keratoplasty may be considered if there is extensive corneal scarring in addition to endothelial failure, or if endothelial keratoplasty is not suitable.

While PBK can be a concerning complication after cataract surgery, advances in endothelial keratoplasty — particularly DMEK — have dramatically improved the prognosis. Careful pre-operative assessment of corneal health and meticulous surgical technique during cataract surgery are important in minimising the risk. For those who do develop PBK, effective treatment is available.