DSEK / DSAEK
DSEK (Descemet’s Stripping Endothelial Keratoplasty)
Suture-less Corneal Transplant
The cornea is the clear, living tissue on the very front part of the eye. Light passes through the clear cornea on its path toward the retina in the back part of the eye. Sometimes, the cornea is referred to as the "window" to the eye.
Occasionally, either through disease or injury, the corneal tissue is damaged to a point where light can no longer effectively pass through it, resulting in reduced vision. When indicated, an ophthalmologist can perform a corneal transplant procedure, to replace the damaged cornea with a clear donor cornea. This is an extremely delicate microsurgical procedure.
What is DSEK?
DSEK is a corneal transplant technique where the unhealthy, diseased, posterior portion of a patient’s cornea is removed and replaced with healthy donor tissue obtained from the eye bank. Unlike traditional corneal transplant surgery known as penetrating keratoplasty (PKP), the DSEK procedure utilizes a much smaller surgical incision and requires no corneal sutures. This usually results in more rapid visual rehabilitation for the DSEK patient. The alternative name for DSEK is DSAEK (Descemet’s Stripping Automated Endothelial Keratoplasty).
Who is a Candidate?
DSEK is indicated for those patients who have corneal disorder located on the backside of their cornea known as the endothelial layer. The endothelial layer of the cornea is a monolayer (single layer) of cells lining the back (interior) surface of the cornea. The cells are attached to a membrane called Descemet’s membrane. A healthy endothelial layer consists of small, hexagonally shaped cells with a density of 2500 to 3000 cells/mm2.
Figure 1a - Healthy monolayer of endothelial cells attached to Descemet’s membrane. Red line in the leftmost figure represents Descemet’s membrane and endothelium. The middle diagram represents an enlargement of a cross section from top to bottom that includes the epithelial layer (a), stromal layer (b), Descemet’s membrane with attached monolayer of endothelial cells (c) and anterior chamber (d). The rightmost diagram illustrates normal size and shape of healthy endothelial cells.
When endothelial cells are healthy, they pump fluid out of the cornea. You are born with a fixed number of endothelial cells, and cells are gradually lost with aging. They are also lost through injury, acute glaucoma, intraocular surgery (such as cataract surgery) or inflammation. Many patients have an inborn disease of the corneal endothelium known as Fuchs' Endothelial Dystrophy, where they are either born with a relatively low number of cells, or they are lost more rapidly than normal.
If not enough healthy cells are present the cornea will over-hydrate and become cloudy. Vision eventually deteriorates to a point where these patients feel like they are looking through wax paper. Such patients are good candidates for the DSEK procedure.
Figure 1b - Unhealthy monolayer of endothelial cells attached to Descemet’s membrane. The middle diagram illustrates a cross section of an over hydrated swollen cornea. The top layer of surface (epithelial) have become so swollen that small blisters (bullae) have formed (a). The stroma is thickened with fluid filled pockets (b). A sparse covering of stressed endothelial cells lies over a thickened Descemet’s membrane (c). The right figure depicts large, low density, irregularly shaped endothelial cells.
Traditional Penetrating Keratoplasty
The goal of surgery is to provide new, healthy endothelial cells from a donor cornea. In traditional corneal transplant surgery (PKP) the central portion of your cornea is removed and replaced with a similar portion from a donor eye, with healthy cells on the inner surface. The cornea is slow to heal, and sutures must be left in place for 1 year or longer. New glasses cannot be prescribed for 6 to 15 months. The shape of the corneal surface is altered, and that slows recovery of vision. It also usually means that you need strong glasses or a hard contact lens in order to see well.
Figure 2 - Traditional penetrating corneal transplant (PKP)
Description of the DSEK Corneal Transplantation Procedure
The first part of the DSEK procedure involves removal of the unhealthy endothelial cells and attached Descemet’s membrane. The second part of the procedure involves replacing this unhealthy tissue with a thin layer of corneal tissue with healthy endothelial cells from a donor eye.
The surgery is often done under numbing eye drops under anesthesia monitor. Sometimes local anesthesia is used. In this case the IV sedation renders the patient totally unconscious for about 1 to 2 minutes. During this time a local anesthetic is given to completely numb the eye. When the patient awakes, the sensory nerves of the eye have been blocked so the patient will not feel or see anything during the procedure.
After the local anesthetic has taken effect, the patient is taken to the operating room and the eye is draped in a sterile fashion. DSEK is a microsurgical technique that is performed under a special operating microscope. The first step of the operation involves making a very small (5mm) incision outside the edge of the cornea. Another instrument called an anterior chamber (AC) maintainer is also placed at the temporal aspect of the limbus (3 o’clock). The AC maintainer is an irrigating port that infuses sterile saline into the anterior chamber of the eye and maintains the eye’s shape during the operation. The inner most layer of the cornea is marked, stripped and removed from the eye. A thin layer of donor cornea is folded, inserted and unfolded by using air. It is left in place to hold the donor tissue in place.
Figure 3 - Left illustration depicts a keratome making a small incision at the 12 o’clock limbus and an AC maintainer at the 3 o’clock limbus. To the right, the cross sectional figure shows the opening of the AC maintainer within the small blue space which represents the anterior chamber.
Another instrument called an anterior chamber (AC) maintainer is also placed at the temporal aspect of the limbus (3 o’clock). The AC maintainer is an irrigating port that infuses sterile saline into the anterior chamber of the eye and maintains the eye’s shape during the operation.
Figure 4 - Shows a Sinsky hook scoring Descemet’s membrane in a circular motion. The bottom figure illustrates how the AC maintainer keeps the small anterior chamber space formed during the maneuver. The hook breaks or tears through Descemet’s membrane so that the 8mm circle of Descemet’s membrane and unhealthy endothelial cells can be removed.
Figure 5 (right) - Depiction of the delicate stripping of diseased Descemet’s membrane. The actual removal of the circle of Descemet’s tissue is done with a device called a Descemet’s stripper. This device looks like a small garden hoe or rake.
Figure 6 (left) - Illustration of removal of an 8mm circular disk of diseased Descemet’s membrane from the anterior chamber through the tiny incision site. The figure on the right is a cross sectional view of the same maneuver.
Preparation of the donor tissue has been greatly facilitated by the use of the microkeratome. The microkeratome has been used for decades in refractive surgery and is most commonly used today to cut the flap in LASIK surgery. The microkeratome works like a mini-carpenter’s plane. The microkeratome can be adjusted to cut various thicknesses of cornea.
For the DSEK procedure the thickness of the cut removes the top 80-90% of the cornea. The bottom 10-20% is then used to prepare an 8-9mm disc of donor tissue. This donor tissue is machine cut rather than hand cut and has a very smooth surface which enhances visual recovery. The endothelial cells of the donor tissue are coated with a protective gel and then the donor disc is folded like a taco with the endothelial cells on the inside.
Figure 7 - DSEK donor tissue has been inserted into the anterior chamber and the gentle flow of fluid from the AC maintainer is used to unfold the taco. The left figure shows a cross section of the same.
After the tissue has been unfolded it is positioned to cover the area of the previously stripped Descemet’s membrane. Then the anterior chamber is filled with air.
Figure 8 (right) - Shows a cross sectional view of the injection of air into the anterior chamber from a cross sectional view. The air filled anterior chamber is needed to hold the transplant tissue in position.
Figure 9 (right) - Depicts anterior chamber full of air with a well-positioned DSEK transplant.
The small incision site is self-sealed and often does not need sutures. The patient is then sent to the recovery room where the patient lies on his back, face up, for one hour so that the air in the anterior chamber can help fix the transplant into place. A small amount air bubble is left in the eye. The air is slowly absorbed over 1-2 days. The patient is then sent home with instructions to return the following day.
Figure 10 - The DSEK transplant is in excellent position with small incision. Note that there are no corneal sutures present which helps to minimize post-operative astigmatism.
Advantages and Disadvantages of the DSEK Procedure
The incision into the eye is smaller in DSEK than in traditional PKP. This incision heals more quickly and is a little safer, since it reduces the risk of sight threatening complications such as intra-operative expulsive hemorrhage or post-operative traumatic wound rupture. Typically after PKP you will need strong glasses or a hard contact lens to see well; this is not the case with DSEK. DSEK does little to change the pre-existing glass prescription.
However, there are some trade-offs: with DSEK vision is often slightly reduced by haze developing between the donor tissue and your cornea. Also there is about a 10% chance that the donor tissue will dislocate during the first night after surgery. If this occurs the donor tissue must be re-floated into position in the office.
Frequently Asked Questions About DSEK
Where is the procedure performed?
DSEK is performed in an outpatient surgery center. No hospitalization is required.
How long does the procedure last?
The total time the patient will be in the surgery center is approximately 2 to 3 hours. Once the patient is taken to the operating room the procedure is completed in about 45 minutes. Additional time may be necessary if other procedures are also planned ie cataract surgery or intraocular lens replacement. After the procedure is completed the patient is taken to the recovery room where they must lie on their back for 45 to 60 minutes. This allows the air that has been placed in the anterior chamber of their eye to fix the transplant into position.
When will I need to return for a follow-up office visit?
The first office visit is scheduled the day after the DSEK procedure has been completed. During this visit the health and position of the new transplant will be checked. If everything is in proper order you will start your post op eye drops as directed and return for a follow up visit in one weeks.
What type of eye drops will I need after surgery?
You will continue using antibiotic and anti-inflammatory(similar to motrin)eye drops that you started three days prior to surgery. You will also use a steroid eye drop until otherwise instructed. The steroid drops are required to prevent rejection of your new transplant. Most patient can stop after one year. Some will continue for the entire life. If you are also using glaucoma eye drops continue to use them after surgery unless otherwise instructed.
When will I see an improvement in my vision?
Visual recovery varies depending on the severity of your corneal cloudiness prior to surgery. Most patients notice improvement in their vision during the first two weeks after surgery with continued improvement during the next four to six weeks. This recovery represents a dramatic improvement over the time required following conventional corneal transplant surgery (PKP), which usually takes six to twelve months. Some DSEK patients may not notice visual improvement as quickly as they would like, because they have other ocular conditions such as cataract or retinal problems that must be addressed.
Can my DSEK transplant undergo rejection?
Although the rate of rejection with DSEK does not appear to be any higher than rejection rates with PKP, endothelial rejection can occur following DSEK. The signs and symptoms of such rejection episodes are the same as they are for PKP patients. Briefly, if you experience redness, photophobia (light sensitivity) and blurred vision assume that you are having a rejection episode and call my office so that you can be evaluated immediately. Most rejection episodes are successfully terminated by using steroid eye drops. The sooner a rejection is treated the better chance for transplant survival.