Advances with DMEK

[caption id="attachment_5830" align="alignnone" width="180"] Donald Tan MD[/caption] New techniques and instruments are needed to make Descemet’s membrane endothelial keratoplasty (DMEK) less challenging and more reliable, Donald TH Tan FRCS told the 2016 ASCRS•ASOA Symposium & Congress in New Orleans, USA. Dr Tan, a corneal surgery pioneer and current President of the Asia Cornea Society, believes these advances will occur, and DMEK and other lamellar surgeries will continue to supplant full-thickness penetrating keratoplasty (PK) for many indications. “Lamellar surgery is a revolution, but it is still in evolution,” he said. DMEK is currently controversial. Because it adds no excess stroma, it generally delivers better visual outcomes – but at the cost of higher complications than Descemet’s stripping automated endothelial keratoplasty (DSAEK), Dr Tan said. “What’s more important, the extra line of visual acuity or endothelial cell loss?” IMPROVED OUTCOMES However, DMEK is currently in its infancy as a procedure while DSAEK is mature, benefitting from years of refinement dramatically improving outcomes, Dr Tan noted. For example, the Singapore National Eye Centre, where he practises with a series of improved DSAEK techniques and instruments, reduced endothelial cell loss from 60 per cent in early cases to 15 per cent now. The biggest problem in DMEK is handling donor Descemet’s tissue. Because it is so delicate and flimsy, it is hard to unscroll and place without damaging it using nothing more than an intraocular lens inserter BSS, and an air bubble, Dr Tan said. The solution may be to utilise a small amount of stroma to improve handling characteristics, and use inserters designed for DSAEK such as the EndoGlide to maintain better control during surgery – the stroma acts as a carrier, but only the donor DM graft is pulled into the eye – a procedure he calls hybrid DMEK. In his first 14 hybrid DMEK cases, Dr Tan saw a mean endothelial cell loss of 28 per cent, with no graft failures or dislocations. That compares with 60 per cent cell loss with one graft failure and three re-bubblings in his first 15 straight DMEK cases, and 40 per cent cell loss with no graft loss or re-bubbling in his second 15 straight DMEK cases. Dr Tan believes developments such as this hybrid approach could reduce DMEK complications, just as development dramatically reduced cell loss and graft rejection in DSAEK. As visual outcomes improve and complications recede, better procedures will drive greater acceptance of all types of lamellar surgery worldwide. “DMEK epitomises the current distillation of our ability to replace the corneal endothelium, but the surgery needs to evolve with improvements in surgical techniques or instrumentation before the tipping point for widespread adoption can be achieved,” Dr Tan concluded. Donald TH Tan: donald.tan.t.h@singhealth.com.sg