DSEK vs PKP: Which Is Best, and Why?
Preparing the DSEK tissue is more complicated than preparing a PKP button, with potentially greater damage to the endothelium. Insertion of the DSEK tissue into the eye, whether it is being folded, pulled, or pushed through the incision, is more traumatic to the endothelium than suturing a PKP button. Centering the DSEK graft and then leaving an air bubble in the anterior chamber are also potentially damaging to the endothelium. Finally, rebubbling of a dislocated DSEK graft, which was more common in the early days of this procedure, increases the risk for endothelial cell loss. Consequently, it shouldn't be surprising that when I started doing DSEK almost 10 years ago, I shared with others the concern that this new procedure might result in surgical trauma to the endothelium.
Early research confirmed these suspicions. Many of the initial reports on DSEK showed very high rates of endothelial cell loss in the first 3-12 months after surgery. The 1-year data from the patients in this study also showed greater cell loss in the DSEK group vs the PKP group. To our amazement, this study now demonstrates less endothelial cell loss in the DSEK eyes than in the PKP eyes in the subsequent 2 years. This lower rate of endothelial cell loss in DSEK eyes (from earlier series) compared with the PKP eyes continues for 3-5 years. The reason for this phenomenon is still unknown.
This report and others have furnished more good news about DSEK. Compared with PKP, DSEK is associated with significantly lower immunologic graft rejection rates. The reasons for this are certainly multifactorial but probably involve, to a large degree, the lower antigenic load in the DSEK eyes.
The study by Price and colleagues reinforces the fact that squeezing tissue through small incisions causes more endothelial cell loss, seen at 1 year and continued at 3 years. The 5.0-mm incision used in the DSEK eyes was associated with significantly less endothelial cell loss than the PKP eyes at 3 years. Small incisions are advantageous for many reasons; they induce less astigmatism and lead to a more stable wound that is less resistant to accidental trauma. For this reason, new techniques and instruments, including glides and inserters, have been developed to more safely insert DSEK grafts through relatively smaller incisions. Although these products may increase the cost of the DSEK surgery, their aim is to make it a safer procedure by further reducing surgically induced endothelial cell loss.
Many corneal surgeons who converted relatively early from PKP to DSEK did so to achieve more rapid visual recovery, less induced refractive error (both astigmatism and spherical equivalent), less suture manipulation, and a much stronger wound. We assumed that the surgery itself would cause more endothelial cell loss than PKP, but the advantages outweighed this disadvantage. In fact, we believed that even if we needed to repeat the DSEK grafts more frequently, the advantages of DSEK still outweigh those of PKP. Corneal surgeons are excited to learn that the long-term endothelial cell loss after DSEK appears to be even lower than after PKP. We are all hoping that these new data indicate that DSEK grafts will survive as long as PKPs, if not longer.
Abstract
Viewpoint
Preparing the DSEK tissue is more complicated than preparing a PKP button, with potentially greater damage to the endothelium. Insertion of the DSEK tissue into the eye, whether it is being folded, pulled, or pushed through the incision, is more traumatic to the endothelium than suturing a PKP button. Centering the DSEK graft and then leaving an air bubble in the anterior chamber are also potentially damaging to the endothelium. Finally, rebubbling of a dislocated DSEK graft, which was more common in the early days of this procedure, increases the risk for endothelial cell loss. Consequently, it shouldn't be surprising that when I started doing DSEK almost 10 years ago, I shared with others the concern that this new procedure might result in surgical trauma to the endothelium.
Early research confirmed these suspicions. Many of the initial reports on DSEK showed very high rates of endothelial cell loss in the first 3-12 months after surgery. The 1-year data from the patients in this study also showed greater cell loss in the DSEK group vs the PKP group. To our amazement, this study now demonstrates less endothelial cell loss in the DSEK eyes than in the PKP eyes in the subsequent 2 years. This lower rate of endothelial cell loss in DSEK eyes (from earlier series) compared with the PKP eyes continues for 3-5 years. The reason for this phenomenon is still unknown.
This report and others have furnished more good news about DSEK. Compared with PKP, DSEK is associated with significantly lower immunologic graft rejection rates. The reasons for this are certainly multifactorial but probably involve, to a large degree, the lower antigenic load in the DSEK eyes.
A Smaller Incision: Pros and Cons
The study by Price and colleagues reinforces the fact that squeezing tissue through small incisions causes more endothelial cell loss, seen at 1 year and continued at 3 years. The 5.0-mm incision used in the DSEK eyes was associated with significantly less endothelial cell loss than the PKP eyes at 3 years. Small incisions are advantageous for many reasons; they induce less astigmatism and lead to a more stable wound that is less resistant to accidental trauma. For this reason, new techniques and instruments, including glides and inserters, have been developed to more safely insert DSEK grafts through relatively smaller incisions. Although these products may increase the cost of the DSEK surgery, their aim is to make it a safer procedure by further reducing surgically induced endothelial cell loss.
Many corneal surgeons who converted relatively early from PKP to DSEK did so to achieve more rapid visual recovery, less induced refractive error (both astigmatism and spherical equivalent), less suture manipulation, and a much stronger wound. We assumed that the surgery itself would cause more endothelial cell loss than PKP, but the advantages outweighed this disadvantage. In fact, we believed that even if we needed to repeat the DSEK grafts more frequently, the advantages of DSEK still outweigh those of PKP. Corneal surgeons are excited to learn that the long-term endothelial cell loss after DSEK appears to be even lower than after PKP. We are all hoping that these new data indicate that DSEK grafts will survive as long as PKPs, if not longer.
Abstract