Endothelial keratoplasty is an advanced corneal transplant that replaces only the diseased inner layer of the cornea, known as the endothelium. This single layer of cells is responsible for pumping fluid out of the cornea to keep it clear. When these cells fail, the cornea becomes waterlogged and cloudy, impairing vision. By selectively replacing just this inner cell layer, the surgery restores corneal clarity and improves sight while leaving the healthy parts of the cornea intact, providing a targeted solution for issues originating specifically in the endothelium.
Conditions Treated by Endothelial Keratoplasty
The primary reason for endothelial keratoplasty is the failure of the corneal endothelium, which leads to a swollen cornea known as corneal edema. The most common cause is Fuchs’ Endothelial Corneal Dystrophy, a progressive genetic disorder that causes a gradual die-off of endothelial cells. As cell density decreases, the layer’s pumping function becomes insufficient, and vision deteriorates, often first noticed as morning misting that clears as the day progresses.
Another condition treated by this surgery is Pseudophakic Bullous Keratopathy. This occurs when the endothelium is damaged during a previous eye surgery, most often cataract removal, leading to irreversible corneal edema. Endothelial keratoplasty is also an effective treatment for failed previous corneal transplants where the donor endothelium has ceased to function over time, and for other less common endothelial disorders.
Types of Endothelial Keratoplasty
There are two main types of endothelial keratoplasty: Descemet’s Stripping Endothelial Keratoplasty (DSEK) and Descemet’s Membrane Endothelial Keratoplasty (DMEK). Both procedures involve removing the patient’s diseased endothelium and its adjoining membrane, called Descemet’s membrane. The difference between them is the composition and thickness of the donor tissue, which influences surgical complexity and visual outcomes.
In DSEK, the transplanted tissue includes the donor endothelium, Descemet’s membrane, and a thin supporting layer of corneal stroma. This makes the graft thicker, around 20-30% of the cornea’s total thickness, and easier for the surgeon to handle and position within the eye. Because of its relative ease, DSEK has been a widely adopted technique.
DMEK is a more advanced procedure that involves transplanting only the endothelial cells and Descemet’s membrane, without any stromal tissue. The resulting graft is exceptionally thin, at just 5 to 10 microns thick. This anatomical precision leads to better visual outcomes, with many patients achieving 20/20 vision. However, the fragility of the tissue makes the surgery more challenging and increases the risk of the graft dislocating, which may require a second procedure, known as re-bubbling, to reposition it.
The Surgical and Recovery Process
Endothelial keratoplasty is an outpatient procedure performed under local anesthesia that takes about an hour. The surgeon makes a small incision in the white of the eye, the sclera, to remove the patient’s diseased endothelial layer. The prepared donor tissue is then folded, inserted into the eye, and unfolded.
An important step is the injection of an air or gas bubble into the eye. This bubble presses the new donor tissue against the patient’s cornea, holding it in place so it can adhere. The small incision is self-sealing or may require a few stitches. Patient positioning after surgery is important for a successful outcome.
Recovery begins immediately, with patients required to lie flat on their backs for the first 24 to 48 hours. This positioning allows the bubble to provide maximum support to the graft. Post-operative care involves antibiotic and steroid eye drops to prevent infection and reduce inflammation. Patients are advised to avoid strenuous activities, heavy lifting, and anything that could cause a direct impact to the eye for several weeks. Vision is blurry at first but begins to clear within the first few weeks, with significant improvement over the next three to six months.
Comparing Endothelial Keratoplasty to Traditional Transplants
Endothelial keratoplasty offers several advantages over the traditional full-thickness corneal transplant, known as Penetrating Keratoplasty (PK). The primary difference is the wound size. EK uses a small, self-sealing incision, while PK requires a large, 360-degree incision secured with many sutures. This smaller incision in EK leads to a structurally stronger eye that is less prone to injury after surgery.
The preservation of the patient’s cornea in EK contributes to faster visual recovery. Traditional PK results in high levels of astigmatism from the sutures, which can delay clear vision for a year or more. In contrast, EK patients experience functional vision much more quickly, with less dependence on glasses or contacts to correct astigmatism.
Because EK involves transplanting a smaller amount of donor tissue, the risk of the body’s immune system rejecting the graft is significantly lower compared to PK, making this complication less frequent. These combined benefits have established endothelial keratoplasty as the preferred surgical approach for treating disorders confined to the corneal endothelium.