How to perform DMEK: An introductory guide for young ophthalmologists

The challenges of the technique can be successfully overcome with a few simple maneuvers.

Corneal transplant techniques have been continuously evolving, and this has translated into patient benefits including quicker recovery, better vision and satisfaction. However, some new surgical techniques are particularly challenging and have a steep learning curve. This month, Martin Dirisamer and Ricarda Konder — who both worked closely with Gerrit Melles, the inventor of the procedure — tell us about endothelial keratoplasty techniques and tips for how to make the learning curve shorter and less stressful. – Anthony Khawaja, MB BS, MA(Cantab), MPhil, FRCOphth, Chair of the SOE Young Ophthalmologists committee

Various clinical procedures are available to the corneal surgeon when dealing with endothelial disease. For nearly a century, the most widely used surgical technique for treating conditions such as Fuchs’ endothelial dystrophy was penetrating keratoplasty. Later, posterior lamellar keratoplasty was developed and became known worldwide as Descemet’s stripping (automated) endothelial keratoplasty. The ultimate simplification of the procedure was Descemet’s membrane endothelial keratoplasty, which was first developed at the Netherlands Institute for Innovative Ocular Surgery by Gerrit Melles, MD, PhD, and is the first stroma-free transplant technique in keratoplasty. The key step of this procedure, and subsequently the inherent reason for its widespread success, is the replacement of only the endothelium and Descemet’s membrane, giving way to fast recovery, low rejection rates, minimal side effects, and the possibility of using the anterior donor tissue for other surgeries such as deep anterior lamellar keratoplasty.

For ophthalmologists just starting out, DMEK may present numerous challenges. The main complications are intraoperative, such as erroneously implanting the graft upside down when positioning it in the anterior chamber, and postoperative, such as partial or complete graft detachment. Because the operation may be accompanied by a significant elevation in IOP, a preoperative iridotomy should be performed before DMEK. To further minimize common risks, the anterior chamber is left with 100% air fill for 60 minutes after surgery; this promotes graft adhesion and, consequently, minimizes the risk of detachment.

Measures and precautions

Preoperative

1. Choose pseudophakic eyes with Fuchs’ endothelial dystrophy for first surgeries.

2. Orient the patient in the anti-Trendelenburg position.

3. Obtain a soft eye through manual massage for at least 2 minutes. A Honan balloon is also used for 10 to 15 minutes afterward.

Intraoperative

1. Stain the graft thoroughly at least two to three times; the disappearance of color intensity will set the time frame for the operation after insertion.

2. Use glass instruments for the surgery.

3. Check correct configuration (double roll) and orientation of the graft before and after insertion. Use Moutsouris sign to confirm that the graft flaps are pointing upward; if they are not, flip the graft through repeated bursts of balanced salt solution.

4. Maintain structural support of the anterior chamber with the air bubble; this also allows for better visualization.

Postoperative

1. Leave the anterior chamber with 100% air fill for 60 minutes.

2. Reduce the air fill after 60 minutes to 30% to 50%; the patient can then leave.

3. Conduct regular follow-ups to check graft attachment and visual acuity.

Results with DMEK

Postoperative visual acuity was groundbreaking for this surgical procedure: 77% of patients were reported to achieve a best corrected visual acuity of 20/25 or better. Often, a BCVA as good as 20/20 is achieved within 1 week of surgery. Graft detachment may be a complication, but it reaches clinical significance relatively infrequently, and it has been shown that even with large and central detachments, a BCVA of 20/40 can still be attained. Reintervention is required in only 11% of operated eyes. Rejection rates remain low after 2 years and are currently observed to occur in 1% to 2% of cases. This is likely due to the thin stroma-free graft, which, because of the reduced surface area, is less likely to provoke an autoimmune response.

Despite the risks involved in performing DMEK, a recent study showed that even a novice surgeon tended to obtain promising postoperative results. Out of 23 patients treated by the same ophthalmologist, 19 (83%) reached BCVA of 20/40 at 6 months after surgery, 11 (48%) reached 20/28 and seven (30%) reached 20/20. More interestingly, these results were obtained despite the lack of an in-house eye bank, thus adding to the stress of surgery by preparing the graft from scratch. It is therefore highly encouraged that young ophthalmologists familiarize themselves with the DMEK technique, which continuously provides exceptional quantitative and qualitative results.

As a result of the standardization of this surgical procedure, there is a continual effort toward providing worldwide access to the technique. Real-time instructional videos, narrated in a stepwise manner by corneal surgeons at NIIOS, are available online at www.youtube.com/user/NIIOSonVideo and www.niios.com. Furthermore, ophthalmologists from across the world are encouraged to attend regularly offered instructional sessions at NIIOS, and fellowship positions are available for ophthalmic surgeons who want to pursue specialization in the DMEK procedure.

• References:
• Dapena I, et al. Arch Ophthalmol. 2011;doi:10.1001/archophthalmol.2010.334.
• Dirisamer M, et al. Arch Ophthalmol. 2012;doi:10.1001/archophthalmol.2011.343.
• Droutsas K, et al. Cornea. 2013;doi:10.1097/ICO.0b013e31828f0e3c.
• Melles GRJ. Cornea. 2006;doi:10.1097/01.ico.0000243962.60392.4f.
• Parker J, et al. US Ophthalmic Review. 2013;6(1):29-32.
• Tan DT, et al. Lancet. 2012;doi:10.1016/S0140-6736(12)60437-1.
• van Dijk K, et al. Cont Lens Anterior Eye. 2013;doi:10.1016/j.clae.2012.10.066.
• Martin Dirisamer, MD, can be reached at Department of Ophthalmology, General Hospital Linz, Austria; email: dirisamer@me.com.
• Ricarda M. Konder can be reached at the Netherlands Institute for Innovative Ocular Surgery, Melles Cornea Clinic Rotterdam, The Netherlands; email: ricarda.konder@unb.ca.
• SOE Young Ophthalmologists website: http://soevision.org/yo

Disclosure: The authors have no relevant financial disclosures.