January 2018

COVER FEATURE

All you need to know about cornea transplants
Surgical pearls for DMEK


by Ellen Stodola EyeWorld Senior Staff Writer


A DMEK triple procedure, with cataract extraction, IOL implantation, and DMEK
Source: Peter Veldman, MD

Surgeons discuss their approach to DMEK to help improve outcomes

When performing Descemet’s membrane endothelial keratoplasty (DMEK), there are a number of details for surgeons to pay attention to for a successful surgery. Leejee H. Suh, MD, associate professor of clinical ophthalmology and director of the Laser Vision Correction Center, Edward S. Harkness Eye Institute, Columbia University, New York, W. Barry Lee, MD, Eye Consultants of Atlanta, and Peter Veldman, MD, assistant professor, residency program director, and vice chair for education, Department of Ophthalmology and Visual Science, University of Chicago Medicine & Biological Sciences, shared some of their surgical pearls for DMEK.

Matching the donor with recipient size

Dr. Suh will usually perform a slightly larger descemetorhexis, 8 mm for a 7.75 mm DMEK graft, so there is not much overlap between donor and host.
According to Dr. Veldman, it has been conclusively demonstrated that overstripping, or placing a graft that is smaller than the area of excised recipient Descemet’s membrane, reduces the rate of rebubble in DMEK due to the minimization of graft overlap with native Descemet’s membrane. “Because of this, I always remove slightly more Descemet’s membrane than I implant, typically a 7.5 mm graft inside of an 8 mm stripping,” he said. “I do adjust the graft size, typically smaller, in special circumstances such as under a failed penetrating keratoplasty or when replacing a DSAEK as the available recipient graft bed dictates.”
Dr. Lee uses an 8.5 mm trephine (Katena, Denville, New Jersey) to indent the epithelium of the recipient with centration around the pupil. This is stained with trypan blue. “I remove the Descemet’s membrane and endothelium under the stained epithelial mark and inject donor DMEK tissue trephined at 8 mm so I have a 0.5 mm difference between donor and recipient,” he said.

Pre-marked DMEK tissue

Dr. Veldman said he is a big proponent of pre-marked DMEK tissue, having been involved in the development of the S-stamp. “It has improved the safety margin in DMEK through a reduction in the rate of upside down graft implantations and importantly, in our studies, did not significantly impact clinical outcome parameters, including rebubble rate and 6-month endothelial cell loss.”1,2
He has been heartened by the number of physicians who have told him that the S-stamp enabled their successful and safe adoption of DMEK. “That said, there is some limited regional endothelial trauma induced secondary to the application of the S-stamp, so I will typically position the graft so that the S is superior, allowing more prolonged gas bubble coverage postoperatively,” he said.
Dr. Lee uses pre-marked tissue in all DMEK cases. The eye bank pre-strips the tissue, leaving one marked edge attached, and places an “S” mark on the Descemet’s membrane side.
“I think it is a godsend,” Dr. Suh said of pre-marked tissue. “It facilitates the surgery. For the beginning surgeons where the trypan blue can start to fade with longer unfolding times, the S-stamp will help with orientation.” She only uses S-stamp tissue at this point in her practice.

Cases to watch for early in the learning curve

Dr. Lee suggested avoiding young donor tissue, as it is hard to unscroll in the eye. “Start out with pseudophakic patients rather than combined cataract patients,” he said. Additionally, he suggested avoiding highly myopic eyes with high axial lengths, as well as patients with prior glaucoma surgery.
Dr. Suh said she would avoid any eyes that have very deep anterior chambers, as the tissue is more difficult to unfold. “Also, any eyes that have had glaucoma surgery and vitrectomized eyes are better DSAEK candidates,” she said.
“I stress to surgeons adopting DMEK to avoid eyes that have had prior vitrectomy,” Dr. Veldman said. “Vitrectomized eyes simply do not allow adequate anterior chamber shallowing for those of us who use external tapping techniques.” He added that if you ask experienced DMEK surgeons, they will tell you that some of their most stressful and extended DMEK experiences were on vitrectomized patients. “I am hopeful that this may change in the future with the emergence and ongoing validation of pull-through DMEK techniques that allow direct control of the graft,” he said. “Until then, DSAEK is a great procedure in these eyes in my opinion.”

How to manage the bubble

Dr. Lee makes an inferior iridectomy prior to tissue insertion. “I use 100% air fill once the DMEK tissue is centered and keep the patient flat for an hour in the recovery room, then check in the YAG laser room at the slit lamp and make sure the air clears the iridectomy,” he said. If it does, the patient is discharged. If it does not, he will release a small amount of air at the lamp and let the patient sit flat for 30 more minutes and recheck prior to discharge.
Dr. Veldman typically creates an iridectomy using a scratch down technique, which he subsequently enlarges with intraocular micro-scissors, including removal of a small piece of peripheral iris tissue. “A good peripheral inferior iridectomy allows me to place a large, approximately 90% fill of 20% concentration SF6 gas,” he said. “With an adequate bubble in place, I use my finger to apply pressure to the sclera, with resultant elevation of the intraocular pressure for a few 20–30 second cycles. I will typically have patients position for about 45 minutes, after which they sit up until I can check the adequacy and aqueous clearance of the iridectomy.” If there is not an inferior fluid meniscus that is contiguous with the iridectomy, Dr. Veldman will burp the smallest possible amount of gas from the inferior paracentesis and recheck the patient in 5 minutes, at which point there is typically a visible meniscus.
Dr. Suh uses 20% SF6 and fills up to a large bubble size. She uses the anterior vitrectomy unit to make the inferior iridectomy. “But make sure that when the patient is sitting up and facing forward, there is clearance of the inferior iridectomy,” she said.

References

1. Veldman PB, et al. Stamping an S on DMEK donor tissue to prevent upside-down grafts: laboratory validation and detailed preparation technique description. Cornea. 2015;34:1175–8.
2. Veldman PB, et al. The S-stamp in Descemet membrane endothelial keratoplasty safely eliminates upside-down graft implantation. Ophthalmology. 2016;123:161–4.

Editors’ note: The physicians have no financial interests related to their comments.

Contact information

Lee
: wblee@mac.com
Suh: lhs2118@cumc.columbia.edu
Veldman: peterbveldman@gmail.com

Surgical pearls for DMEK Surgical pearls for DMEK
Ophthalmology News - EyeWorld Magazine
283 110
220 118
,
2018-01-05T08:34:59Z
True, 1