This nonrandomized prospective study examined the incidence and causes of glaucoma after Descemet membrane endothelial keratoplasty (DMEK) in 275 consecutive eyes. The authors found that DMEK does not increase the risk of uncontrolled glaucoma compared to penetrating keratoplasty (PK) and Descemet stripping endothelial keratoplasty/Descemet stripping (automated) endothelial keratoplasty (DSEK/DSAEK).
However, they conclude based on their findings that eyes with pre-existing glaucoma undergoing DMEK may require close monitoring of postoperative IOP. In eyes without a history of glaucoma, they say that postoperative glaucoma may be avoided in most cases by adjustments in the management of the air bubble in phakic eyes, a steroid regime titrated to the patient population and proper graft positioning. Incidental cases may be related to the presence of an angle-supported (phakic) intraocular lens, or peripheral anterior synechiae formation in eyes with a decentered graft causing adhesions between the donor tissue and the iris.
The study included the initial 229 patients that underwent DMEK for Fuchs' endothelial dystrophy (260 eyes) or bullous keratopathy (15 eyes) at one tertiary referral center. Of this group, 18 eyes (6.5 percent) showed postoperative glaucoma after DMEK, two of which required surgery. Mean follow-up was 22 months.
Seven eyes (2.5 percent) experienced an exacerbation of pre-existing glaucoma. Eleven eyes (4 percent) presented with a de novo IOP elevation; this was associated with an air bubble-induced mechanical angle closure in 2 percent, steroid response in 0.7 percent and peripheral anterior synechiae in 0.4 percent.
At six months, all eyes had a BCVA of ≥20/40, and 81 percent reached ≥ 20/25. Mean endothelial cell density was 1,660 (± 554) cells/mm2 (n = 15) (P > 0.1).
The authors note that only 55 eyes (20 percent) were phakic, so air bubble-induced secondary angle-closure glaucoma may have occurred in a relatively high incidence of cases, that is, in 11 percent (6/55). They recommend pressurizing the anterior chamber with a complete air fill for about one hour at termination of DMEK, and then reducing the air fill to only 20 to 30 percent (instead of 50 percent) in phakic eyes. Since phakic eyes represent a younger age group and a Descemet graft may adhere more easily in younger patients, this change in protocol may better balance the risk of graft detachment with that of air bubble-induced angle-closure glaucoma.