Corneal Transplant With DMEK Faster and Possibly Better

CHICAGO, Illinois — Descemet membrane endothelial keratoplasty (DMEK) offers rapid and near-complete visual rehabilitation in patients with corneal endothelial disorders, according to a large prospective study presented here at the American Academy of Ophthalmology 2012 Annual Meeting.

DMEK is a new type of partial-thickness corneal graft in which only the innermost corneal layers are replaced, rather than the whole thickness of the cornea, as happens in a conventional full-thickness graft (i.e., penetrating keratoplasty [PK]). In this latest iteration of endothelial keratoplasty, DMEK replaces only the Descemet's membrane and endothelium, and leaves the patient's cornea closer to its original condition than other transplant techniques.

"DMEK offers near-perfect anatomical restoration of the recipient cornea," said Fayyaz Musa, MD, who did his fellowship at the Netherlands Institute for Innovative Ocular Surgery (NILOS), where the study was conducted. He is now at the Huddersfield and Calderdale NHS Trust in the United Kingdom.

"DMEK offers improved optical quality, fast and often complete visual rehabilitation, fast stabilization of refraction, and small refractive shift," he reported.

Dr. Musa led the study that evaluated visual rehabilitation and postoperative complications after DMEK in 300 eyes (248 patients) with corneal endothelial failure treated at NILOS, one of the centers pioneering the procedure. Of these, 237 eyes were pseudophakic, 63 were phakic, and the remainder had a variety of disorders.

After the exclusion of 79 eyes because of low visual potential, incomplete data, or nonfunctional or detached grafts, 221 eyes were available for the analysis.

Best Corrected Visual Acuity (BCVA) With DMEK

BCVA	Before DMEK, % of Eyes	1 Month After DMEK, % of Eyes	6 Months After DMEK, % of Eyes
≥0.5	38	87	98
≥0.8	7	57	79
≥1.0	1	24	46
≥1.2	0	3	14

"We found that 87% achieved 6/12 vision, or 20/40, which is a very high proportion achieving a good level of vision very early on in recovery," Dr. Musa noted. "By 6 months, nearly 60% were seeing the equivalent of 20/20."

How Does DMEK Compare With Other Transplant Methods?

He compared these outcomes with those reported for PK and for the newer Descemet's stripping automated endothelial keratoplasty (DSAEK), in which only the inner endothelial cell layer is replaced. Studies report that with PK, BCVA of at least 0.5 is achieved in 50% of eyes after 1 year; with DSAEK, BCVA of at least 0.5 is observed in 60% of patients or more after 6 months, he said.

"DMEK shows the potential to have 85% of patients seeing 20/40 and better after only 1 month," Dr. Musa reported.

He credits the "smooth stromal interface" that is created with DMEK as the reason for this. "With DSAEK, there is a clear demarcation line, although this lessens with time. With DMEK, I can hardly tell a graft has been done; it's that good," he said.

Refractive Changes With DMEK

Refractive outcomes were also good, with minimal changes from baseline in the spherical equivalent and cylinder observable at 6 months, he said.

Average spherical equivalent change from baseline to 3 months was an increase of 0.41, from baseline to 6 months was an increase of 0.33, and from 3 months to 6 months was a decrease of 0.08. Average cylinder decrease from baseline to 3 months was 0.34, from baseline to 6 months was 0.36, and from 3 months to 6 months was 0.03. No changes were statistically significant.

"Refractive changes from preoperative levels are about one third of a diopter. Patients are stabilizing their refractive outcomes at 3 months," Dr. Musa noted.

"You do get a refractive shift, but it is minimal compared with what we see with DSAEK," he said. He noted that there is a hyperopic shift of ±1.00 diopter with DSAEK and of ±0.38 diopter with DMEK.

"Initially, the cornea is more edematous, but it settles at 1 month and by 3 months we see complete corneal clearance. We have restored the cornea more or less to its normal anatomy," Dr. Musa explained.

"Graft detachment occurred in 10% of eyes, ocular hypertension occurred in 4%, and secondary cataract developed in 5% of phakic eyes," the researchers report.

Simplifying the Surgery

Bennie H. Jeng, MD, associate professor of clinical ophthalmology and codirector of the cornea service at the University of California, San Francisco, who was not involved in the study, moderated the cornea session and commented on the study for Medscape Medical News.

He explained that most cornea surgeons are not yet doing DMEK corneal transplants "because of the perception that this approach is more difficult and there is a steep learning curve." However, prominent research groups, such as those at NILOS, are demonstrating ways of performing DMEK more simply "so that it can be widely adopted."

"The outcomes with DMEK are encouraging. They show how well these patients can do in terms of vision, lack of complications, and a low rate of rejection," he said. "And it appears the surgery may not be as difficult as it seems," Dr. Jeng noted.

Dr. Musa and Dr. Jeng have disclosed no relevant financial relationships.

American Academy of Ophthalmology (AAO) 2012 Annual Meeting: Abstract PA031. Presented November 12, 2012.