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A step-by-step guide to learning PDEK
These tips will help surgeons adopt this advanced procedure, from training to the first case.
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First performed in India in 2013, pre-Descemet’s endothelial keratoplasty is beginning to gain traction in the United States. In this procedure, the pre-Descemet’s layer, Descemet’s and endothelium are transplanted, resulting in a fast recovery similar to Descemet’s membrane endothelial keratoplasty. In addition, PDEK offers an expanded range of candidates and donor tissue compared with DMEK, as well as an easier procedure for surgeons. To offer my patients the advantages of PDEK, I followed this approach with success.
1. Get hands-on experience.
When I was learning DMEK, preparing the tissue myself, I could see that subtle differences in stripping technique could result in removing an extra microscopic layer, the pre-Descemet’s (Dua’s) layer. Years later, we are using this type of graft to perform PDEK. The surgery is the same, but the graft is stiffer and easier to unroll. If you have not transitioned from Descemet’s stripping automated endothelial keratoplasty to DMEK, your eye bank can ease the transition. Take the time to handle these grafts and get a feel for them. Loading, injecting and unrolling the grafts gave me a good feel for the procedure. My eye bank also has training seminars and wet labs, but most surgeons familiar with DMEK will see that there is no difference in technique — the procedure is just easier to perform and can be offered to a broader range of patients.
2. Identify PDEK candidates.
A lot of complex cases are referred to me for corneal transplant. The patients may have prior capsulotomy, vitrectomy or other surgeries that rule out DMEK. For DMEK to be successful, we must be able to make the anterior chamber very shallow without vitreous coming forward and entangling the graft. A PDEK graft unscrolls with less flattening of the anterior chamber, so we can perform it on patients with previous surgery. More patients than ever before are now candidates for corneal transplants that offer easier recovery.
3. Arrange the prepared tissue.
To prepare PDEK tissue myself would take an hour and present the financial risk of damaging the tissue. Prepared tissue eliminates that time and risk, as eye banks verify that the tissue is viable after the preparation process. My eye bank is Lions Eye Institute for Transplant and Research (LEITR), a Vision Share member facility. I tell LEITR a week in advance that I need tissue for PDEK, and it is delivered to me pre-cut, pre-loaded and stamped to show which side goes up, allowing me to focus on the procedure, not preparing the graft. Because the PDEK graft is thicker and stiffer than one for DMEK, I can use tissue from an expanded pool that includes younger donors. For DMEK, I have had to use donors over age 70. Younger donors often scroll too tightly. Now I can use very young donors. In theory, younger tissue may be healthier and have higher endothelial cell counts.
4. Begin performing PDEK.
The PDEK procedure is no different than DMEK. The patient gets a block. I make a peripheral corneal incision, paracenteses and inflate the anterior chamber with an anterior chamber maintainer. Using a Descemet’s stripper, I strip the host endothelium. I refill the eye with balanced salt solution to clear it of air. I open the bottle from the eye bank, remove the modified Jones tube with graft inside, and attach it to a syringe of my choice. Looking at the graft, I note which way it is rolled and remove the sponge cap. I inject the graft into the eye, suture the corneal wound, and tap to unroll and position it. A Fogla cannula works nicely. Postoperatively, the graft seems to attach more easily with less rebubbling, especially in complex cases. Because the tissue is thin, my patients have been less likely to need steroids in 6 months or a year.
In December 2016, I performed the first PDEK using prepared tissue in the United States. The graft was provided by LEITR/Vision Share, which prepared the tissue and delivered it preloaded in the injector, ready to use in surgery. My patient had three failed corneal transplants, vitrectomy, YAG capsulotomy, high-dose steroids for rejection and glaucoma uncontrolled on three medications. After months of follow-up, it is clear the procedure was successful. As you start performing PDEK, try using younger donor tissue, and perform the procedure on patients who would not be candidates for DMEK. It will quickly become clear why PDEK has earned the enthusiasm of a growing number of surgeons.
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- Ahad Mahootchi, MD, is medical director of the Eye Clinic of Florida. He can be reached at Eye Clinic of Florida, 6739 Gall Blvd., Zephyrhills, FL 33542; email: am@seebetterflorida.com.
Disclosure: Mahootchi reports no relevant financial disclosures.