The DSAEK (or DSEK)procedure has quickly revolutionized the way in which cornea specialists both evaluate and treat patients with fuchs dystrophy and pseudophakic bullous keratopathy. Despite its rapidly increasing popularity, there is no consensus as to the best technique or best instrumentation to use. This article outlines several of the more common techniques and tools of the trade.
Regardless of technique, the basic tenets are the same; the original descemets membrane must be removed in a circular ring, new donor cornea must be trephined to remove excess stroma and to dissect the new button, this donor button must be delivered into the anterior chamber, and air must be injected to approximate the donor button to the host stroma.
For incisions, some surgeons prefer a small sutureless corneal incison. Others prefer larger corneal incisons, while still many others utilize an astigmatically neutral scleral incision. Removal of the patient's descemet's membrane can be performed over air, fluid, or viscoelastic. A blunt device, typically a reverse sinskey hook, can be used to to score descemet’s membrane. For those surgeons who prefer to dissect the membrane under fluid, the Gorovoy irrigating Descemet's Stripper (Harvey Precision Instruments) can be very useful. An Irrigation/Aspiration handpiece from a phaco setup can be used to remove the membrane/retained viscoelastic, or a blunt scraper can be used. Several examples include the Rosenwasser (Katena Eye Instruments) and Terry (MSI Precision Specialty Instruments) scrapers.
While many surgeons prefer to cut their own DSEK tissue from whole corneas (the standard device used today being the Moria microkeratome), eye banks have become very proficient at preparing pre-cut tissue. Studies performed to this date have not shown a significant change in outcome for patients receiving pre-cut vs physician-cut tissue. Given this data, pre-cut tissue will most likely become the commonplace in DSAEK surgery.
Insertion of the donor cornea is the most debated aspect of the surgery. If performed improperly, devastating endothelial cell loss and primary graft failure will ensue. What is not agreed upon, however, is the best way to manipulate the fragile graft. The original technique involved folding the tissue as a taco and directly inserting the cornea into the anterior chamber. An example of good folding forceps which minimize crush injury to the tissue are the Rosenwasser DSEK Donor Forceps(Katena Eye Instruments). Other surgeons prefer to deliver the tissue over a sheets glide, whether by push-through or suture pull-through. The Busin Endothelial Glide (Katena Eye Instruments) is a funnel shaped cannula which avoids folding of the cornea as well. The future in DSAEK button insertion, however, is likely to be via injection device. Once perfected, these tools will minimize inter-surgeon variability to allow a delivery of tissue via a:
- small incision
- proper orientation
- minimal cell loss
The most commonplace inserter in the US today is the Tan Endoglide (Angiotech)which should be used in conjunction with an anterior chamber maintainer for proper delivery of the tissue. A newer device, the Endoserter (Ocular Systems Inc) received FDA approval and may become the most popular device due to its ease of use.
Once the new corneal tissue is delivered into the eye, and air bubble is left to approximate the donor to the host stroma. Some surgeons leave a complete air bubble and perform a peripheral iridotomy, while others remove up to 70% of the air bubble after ten minutes of complete air fill. Some surgeons will allows place a drop of atropine at the conclusion of the case to minimize post-operative pupillary block.
In spite of all of these points of debate, there is no question that the DSAEK procedure is becoming more popular and surgical results are improving rapidly. With each of these breakthrough techniques and tools, our patients will reap tremendous visual benefits.