Endothelial keratoplasty (EK) is a surgical procedure to remove an endothelium (inner lining of the cornea) that is not functioning correctly and replace it with donor tissue. It can restore vision in conditions such as Fuchs’ dystrophy, iridocorneal endothelial syndrome, bullous keratopathy, and other endothelial disorders.
The procedure also treats other conditions such as keratoconus, graft failure from previous corneal transplant, swelling of the cornea after cataract surgery, the trauma that affects the cornea, and clouding of the cornea. EK is an alternative to the conventional type of corneal transplant, where the cornea’s whole thickness is replaced. In EK, only the diseased corneal layer is replaced while other areas remain intact.
Preparation & Expectation Before Surgery
The patient is advised to have a person drive them home after the procedure. The doctor will explain the risks and benefits associated with EK. The patient undergoes an ocular examination and patient history is taken.
Types, Purpose & Procedure
Three techniques are used in EK. These include Descemet’s stripping and automated endothelial keratoplasty (DSAEK), Descemet’s stripping endothelial keratoplasty (DSEK), and Descemet’s membrane endothelial keratoplasty (DMEK).
In partial-thickness DMEK, the surgeon partially removes the Descemet membrane and endothelium. The surgeon uses a very thin part of the endothelium, about 10-15 microns thick or just 5% of corneal thickness. This procedure does not make use of donor corneal stroma. Direct contact with the tissue can damage the endothelium and cause graft failure, therefore should be avoided.
In the procedure, the surgeon:
- Removes the diseased tissue after the patient has been prepped
- Puts the extracted donor tissue in a solution to have a better look at it
- Places the tissue in an insertion device (like a syringe)
- Inserts the device through the incision previously made to remove the diseased tissue
- Places the new tissue into the eye which often folds. The tissue can unfold on its own or the surgeon can unfold it
- Conducts tests by asking the patient questions to ensure the tissue is correctly placed
- Uses small air bubbles and surgical tools to ensure the graft is correctly placed
- Ensures the eye has the correct amounts of air to hold the tissue in place. Too little or too much can affect the eye
- Sutures the incision
DSEK procedure follows the same process as DMEK except that the surgeon implants back 20-30% of the donor cornea into the patient’s eye.
DSAEK involves the surgeon partially removing the patient’s endothelium and Descemet membrane to replace it with a donor corneal endothelium plus donor corneal stroma. The donor corneal endothelium measures 100-200 thick. No contact with the donor corneal endothelium should be allowed because it can lead to graft failure, and the donated tissue may get damaged.
- Makes a tunneled corneoscleral incision to remove the diseased Descemet membrane and endothelium
- Folds the graft and uses the non-coapting forceps to insert it
- Fills the anterior chamber with air to pressurize the eye
- Closes the wound using three uninterrupted sutures and leaves the tissue undisturbed for about 15 minutes
- Uses cautery to close the conjunctiva
- Removes enough air from the anterior chamber to ensure there is no air behind the iris
- Adds air back into the anterior chamber to achieve a freely mobile bubble and secure the graft
Risks, Side Effects & Complications
Although EK is considered safe for patients with corneal damage, side effects may include:
- Blurred vision
- Sensitivity to light
- Redness of the eye
There are fewer risks associated with endothelial keratoplasty because it utilizes a much smaller incision than in full-thickness transplantation. There are minimal complications involving sutures and fewer cases of astigmatism.
Before the procedure, graft preparation complications can occur, though rare. Because a very tiny part needs to be extracted from the donor cornea, the tissue can be torn, ending with tissue that has an irregular surface. Perforation can also damage the endothelium.
During the procedure, the following complications can arise:
- Endothelial trauma
- Cataract development
- Failure to maintain a full air-fill
- Graft tissue expulsion or flipping
Postoperatively, the following complications can arise:
- Epithelial ingrowth
- Secondary glaucoma
- Cystoid macular edema
- Though rare, endophthalmitis, interface keratitis, and suprachoroidal haemorrhage
- Primary graft failure which is treated with a new EK or penetrating keratoplasty
- Bubble-related complications such as endothelial toxicity, IOL opacification, or air bubble-related pupillary block
- Secondary graft failure in eyes with a significant loss of endothelial cells, such as in a patient who had a previous glaucoma surgery
- Graft dislocation that happens in the first few days. The endothelium will be repositioned with an air injection if it’s completely detached.
- Graft rejection, though rare in EK, with low rates of 4% at three years. The patient is often treated with topical steroids, oral, or subconjunctival steroids. If this fails, a repeat EK can be performed.
After Care, Recovery & Results
The patient will stay in the recovery room for monitoring before being allowed to go home. S/he is advised to lie down facing up for the next 24 hours. The patient has a protective shield placed over the eye. Medications which include antibiotics and steroid eye drops are prescribed and which must be taken during the next few days. A follow-up appointment is scheduled, usually on the next day, then one week, one month, and three months following the procedure.
Visual recovery is much faster in EK than in the conventional method, with most patients noticing vision improvements within the first two weeks of surgery. Vision gets better during the next four to six months compared to the traditional corneal transplant, where vision improvements can take up to 12 months for effective results to be achieved.
A patient achieves a vision of 20/30 or better within a few months, especially if they had no other eye problems. EK improves visual acuity, facilitates replacement of endothelial cell loss, and has recorded better donor corneal graft survival. There is also minimal change in the topography of the corneal curvature. This makes it easier to select an intraocular lens during simultaneous or staged cataract surgery. This also means the patient requires minimal change in glass prescriptions.