Description of the DSAEK Corneal Transplantation Procedure
The first part of the DSAEK procedure encompasses removal of the unhealthy
compromised endothelial cells and attached Descemet’s membrane. The second part
of the procedure involves replacing this unhealthy tissue with healthy cells from a donor cornea. The entire intraoperative procedure is performed in about 20 to 30 minutes.
Approximately 30 minutes before the DSAEK procedure the patient is sedated with
intravenous medication. 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. DSAEK is a microsurgical technique that is performed under a special operating microscope. The first step of the operation involves making a very small (4.5mm) incision at the 12 o’clock position of the corneal limbus using a device called a keratome.
Figure 2 - 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. It is within this small space known as the anterior chamber that the DSAEK procedure is performed. The average height of the anterior chamber is only 3.5mm which explains why the magnification of an operating microscope is needed to perform the delicate microsurgical maneuvers of the DSAEK procedure.
Figure 3 - Depicts 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.
An instrument called the reverse Sinsky hook is inserted through the tiny incision site and into the anterior chamber (Figure 3). The Sinsky hook is shaped like a small hockey stick and the tip of the hook is used to score an 8mm diameter circle on the back of the patient’s cornea. The hook actually breaks or tears through Descemet’s membrane so that the 8mm circle of Descemet’s membrane and unhealthy endothelial cells can be removed.
Figure 4 Depiction of the delicate stripping of diseased Descemet’s membrane with the microsurgical rake. The figure on the right is a cross sectional view of the same maneuver.
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. This microsurgical rake is used to delicately strip away an 8mm diameter circle of diseased Descemet’s membrane with attached endothelial cells. The anterior chamber
maintainer infuses sterile fluid into the eye as Descemet’s membrane is stripped
away. All of these maneuvers are done within the small space of the eye known as the anterior chamber. As Descemet’s membrane is stripped away it is pulled through the small incision site and removed from the eye. This delicate membrane with its attached endothelial cells is only 20 to 30 microns thick! As mentioned earlier the endothelial cells attached to this delicate membrane must function properly to maintain corneal clarity. So once the unhealthy tissue has been stripped off the back of the patient’s cornea it must be replaced with healthy tissue from a donor cornea.
Figure 5 - 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-carpenters plane. The microkeratome can be adjusted to cut various
thicknesses of cornea. For the DSAEK 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 6 - Illustration demonstrating the division of a full thickness cornea into two parts. The top 80% of this divided cornea can be used for anterior lamellar transplants and the bottom 20% is used to prepare donor tissue for DSAEK. This division of tissue is accomplished with a specialized instrument called a microkeratome. Protective gel is placed on the endothelial side of the DSAEK transplant and then it is folded like a taco.
The folded donor tissue is then inserted through the surgical incision site into the anterior chamber of the patient’s eye. Once the folded tissue is inside the eye the anterior chamber maintainer is used to deepen the front of the eye and unfold the tissue through gentle irrigation. The tissue is opened so that the donor endothelial cells are oriented to the posterior or backside of the tissue.
Figure 7 - The taco shaped DSAEK donor tissue is inserted into the anterior chamber through the tiny surgical incision.
Figure 8 - DSAEK 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 bottom 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 9 - 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 10 - Depicts anterior chamber full of air with a well-positioned DSAEK transplant.
The small incision site is closed with 2 or 3 sutures and 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. After one hour the patient returns to the clinic where the air bubble is removed. The patient is then sent home with instructions to return the following day.
Figure 11 - The DSAEK transplant is in excellent position and the small incision is closed with 3 sutures. Note that there are no corneal sutures present which helps to minimize post operative astigmatism.
Read more
What is DSAEK and who is a candidate?
Commonly asked questions about DSAEK
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