Abstract
Purpose: :
To compare the rate of immunologic graft rejection episodes in four types of cornea transplants used for treatment of endothelial dysfunction: penetrating keratoplasty (PK), Descemet stripping endothelial keratoplasty (DSEK), Descemet membrane endothelial keratoplasty (DMEK) and Descemet membrane automated endothelial keratoplasty (DMAEK). All 4 transplant methods include corneal endothelium; in addition, PK has full-thickness donor stroma, whereas DSEK only has posterior stroma, DMAEK only has a 1-mm rim of posterior stroma, and DMEK does not have any donor stroma at all.
Methods: :
Data was collected prospectively on 200 consecutive DMEK and 100 consecutive DMAEK cases; rate and timing of rejection episodes was compared retrospectively with previously reported results in series of 598 DSEK cases and 30 PK cases performed at the same center, using the same postoperative corticosteroid regimen and the same evaluation criteria for rejection episodes. The standard corticosteroid regimen consisted of prednisolone acetate 1% eye drops instilled 4 times daily for 4 months, tapered by a 1 drop per month to once daily and continued indefinitely. The cumulative probability of a rejection episode within 2 years was assessed by Kaplan-Meier survival analysis and the log rank test, and the relative risk of rejection episodes was determined by proportional hazards analysis; these methods take length of follow up into consideration.
Results: :
Overall, 89% of the grafts were performed to treat Fuchs’ endothelial dystrophy, 62% of the graft recipients were female, and 96% were Caucasian; the relative proportions were comparable in all four transplant groups (P=0.20, P=0.08 and P=0.95, respectively, by analysis of variance). At 2 years, the Kaplan-Meier cumulative rejection-free survival rate was 99.4% for DMEK, 95% for DMAEK, 88% for DSEK and 82% for PK, P=0.0007. The relative risk of a rejection episode was substantially higher with PK than with any of the endothelial keratoplasty techniques. The relative risk of experiencing a rejection episode was 6 times lower with DMEK than DMAEK and 2.8 times lower with DMAEK than with DSEK.
Conclusions: :
The relative risk of experiencing an immunologic rejection episode decreased as the amount of donor stromal tissue in the graft decreased, and the risk of rejection was lowest when donor stromal tissue was eliminated. This finding is consistent with studies showing that the corneal endothelium may be relatively immune-privileged. As a result of these findings, a multi-center prospective randomized study has been initiated to determine if corticosteroid strength can be reduced after DMEK to avoid steroid-associated side effects without unduly increasing the risk of graft rejection.
Keywords: cornea: endothelium • immune tolerance/privilege