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Lower rejection rate with DMEK may allow reduced corticosteroid regimen
Relative risk ratio for immunological graft rejection is 15 times lower than DSEK and 20 times lower than PK, study shows.
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The significantly lower rejection rate of Descemet’s membrane endothelial keratoplasty compared to other allograft techniques improves patient care and management, potentially allowing administration of lower doses of corticosteroids, according to one surgeon.
Immunological rejection is a common cause of graft failure, accounting for 27% of the graft failures in his published series of almost 4,000 penetrating keratoplasties, according to Francis W. Price Jr., MD, speaking at the European Society of Cataract and Refractive Surgeons meeting in Milan. Several studies have shown that rejection rate is influenced by patient demographics, corticosteroid regimen and length of the follow-up.
A study by Price and colleagues further investigated probability and risk factors in relation to the layers of transplanted tissue. Full-thickness grafts, as in PK, were shown to have a significantly higher cumulative rate of initial immunologic rejection episodes (18%) through 2 years compared to lamellar grafts with partial stroma and endothelium, as in Descemet’s stripping endothelial keratoplasty (12%).
“The added value of our study was that we had a large cohort of patients with similar demographics and indications for transplant, operated in a single center, with the same corticosteroid regimen,” Price, an OSN Cornea/External Disease Board Member, said.
Francis W. Price Jr.
The next step was to investigate the rejection rate in patients undergoing transplantation of pure Descemet’s membrane and endothelium.
The study
Data of 141 consecutive DMEK eyes were prospectively collected over 2 years. Patients in the DMEK cohort were similar to those in the earlier DSEK and PK cohorts in terms of demographics, selection for transplantation and postoperative corticosteroid treatment.
The cumulative rate of initial rejection episodes was found to be significantly lower with DMEK compared to both PK and DSEK.
“Over a 2-year period, we had a rejection rate of less than 1% with DMEK. DSEK is better than PK to a significant extent, but DMEK is tremendously better than both the other procedures in regard to the incidence of immunologic graft rejection,” Price said.
By proportional hazard analysis, the relative risk ratio for immunological graft rejection at 2 years with DMEK was 15 times lower than DSEK and 20 times lower than PK.
“This makes us aware of the tremendous benefits that DMEK has compared to other techniques,” Price said. “We should now consider it the gold standard.”
Findings from other large series confirm a lower rejection rate with DMEK. Melles and colleagues found a less than 1% 2-year cumulative rejection rate with DMEK. The cumulative rate of initial rejection episodes after DSEK was found to be 10% by Li and colleagues at Devers Eye Institute and 14% by Wu and colleagues at New York Eye and Ear.
Hybrid techniques that leave a small rim of stroma, such as Descemet’s membrane automated endothelial keratoplasty, had a 4% cumulative rate of initial rejection episodes through 2 years, which was in between the rates seen with DMEK and DSEK when the same steroid was used with all three procedures, Price said.
In his more than 850 DMEK cases, Price has only had five rejection episodes, all related to discontinuation of steroids.
What it means
The diminished risk of rejection with DMEK has important implications in relation to the use of steroids.
“It may allow less use of corticosteroids postoperatively, with consequent reduction of side effects such as IOP elevation. With the steroid regimen we use for DSEK, one-third of our patients develop increased pressure in the first year. The onset of ocular hypertension occurs most commonly within the first 4 months, when we use a four-times-a-day topical corticosteroid dosing regimen, but additional patients continue to develop ocular hypertension even as the dosing frequency is reduced. The more steroids you use, the more rapidly the pressure increases,” Price said.
In a multicenter, prospective, randomized study, Price and colleagues are currently analyzing the effects of reduced steroid strength, comparing prednisolone acetate vs. fluorometholone. Outcome measures are the number of immunologic rejection episodes and IOP elevation. To date, 260 eyes have been randomized, with follow-up between 3 months and more than 12 months, and one rejection episode has been reported.
“We hope that DMEK will offer the opportunity to decrease the dose of topical steroids and therefore the incidence of steroid-associated glaucoma,” Price said. – by Michela Cimberle