How to Avoid an Upside-Down Orientation of the Graft during Descemet Membrane Endothelial Keratoplasty?

DMEK surgical training: An instructional guide on various wet-lab methods

Descemet membrane endothelial keratoplasty (DMEK) is a partial-thickness corneal transplantation procedure that involves selective transplantation of the Descemet membrane and endothelium. DMEK offers significant advantages over other keratoplasty techniques, such as faster visual rehabilitation, better final visual acuity due to minimal optical interface effects, lower risk of allograft rejection, and less long-term dependence on topical steroids. Despite all its advantages, DMEK has been found to be more challenging than other corneal transplantation techniques, and its steep learning curve appears to be an obstacle to its widespread use and adoption by corneal surgeons worldwide. DMEK surgical training laboratories (wet labs) provide a window of opportunity for surgeons to learn, prepare, manipulate, and deliver these grafts in a risk-free environment. Wet labs are a significant learning tool, especially for those institutions that have limited tissue availability in their local centers. We provide a step-by-step guide for preparing DMEK grafts using different techniques on human and nonhuman models with instructional videos. This article should eventually help the trainees and the educators understand the requirements for performing DMEK and conducting a DMEK wet lab and develop their skills and interests from a wide variety of available techniques.

Automatic evaluation of graft orientation during Descemet membrane endothelial keratoplasty using intraoperative OCT

Correct Descemet Membrane Endothelial Keratoplasty (DMEK) graft orientation is imperative for success of DMEK surgery, but intraoperative evaluation can be challenging. We present a method for automatic evaluation of the graft orientation in intraoperative optical coherence tomography (iOCT), exploiting the natural rolling behavior of the graft. The method encompasses a deep learning model for graft segmentation, post-processing to obtain a smooth line representation, and curvature calculations to determine graft orientation. For an independent test set of 100 iOCT-frames, the automatic method correctly identified graft orientation in 78 frames and obtained an area under the receiver operating characteristic curve (AUC) of 0.84. When we replaced the automatic segmentation with the manual masks, the AUC increased to 0.92, corresponding to an accuracy of 86%. In comparison, two corneal specialists correctly identified graft orientation in 90% and 91% of the iOCT-frames.

Clinical results after single asymmetrical shark fin for graft orientation in DMEK

PURPOSE

Evaluating the effect of a single peripheral triangular mark to ensure the correct anterior-posterior graft orientation in DMEK.

METHODS

Retrospective study of patients scheduled for DMEK due to Fuchs endothelial dystrophy and divided into 2 study groups: Group -M (n = 184) had no mark of the EDM (Endothelial Descemet membrane) and group + M (n = 193) had a triangular peripheral mark. Follow-up time was 1 year after surgery.

RESULTS

The postoperative graft turning and Re-DMEK rate could be significantly reduced by the use of a peripheral mark (p = 0.002, p = 0.001, respectively). Re-DMEK due to primary graft failure was significantly associated with prior graft turning (p < 0.001). Both groups showed comparable values for visual acuity, central corneal thickness and endothelial cell count after a follow-up of 1 year.

CONCLUSION

Single peripheral triangular marking is a simple and cost-saving addition to EDM preparation to ensure the correct orientation of the graft intraoperatively and could lead to a significant reduction in graft turning and re-DMEK rate in this study.

Comparison of DMEK and DSAEK in Eyes With Endothelial Decompensation After Previous Penetrating Keratoplasty

PURPOSE

Posterior lamellar keratoplasty is increasingly applied in patients with endothelial decompensation after penetrating keratoplasty (PK). The aim of this study was to compare the results of Descemet membrane endothelial keratoplasty (DMEK) and Descemet stripping automated endothelial keratoplasty (DSAEK) after PK.

METHODS

In this retrospective study, clinical data of 30 patients who received DMEK (n = 19) or DSAEK (n = 11) for endothelial decompensation after PK were evaluated. All lamellar keratoplasties were performed at the Department of Ophthalmology at University Hospital Mainz, Germany. Primary end point included best-corrected visual acuity, and secondary end points included endothelial cell density, rebubbling, and rejection rates, all at 6 and 12 months.

RESULTS

After 6 months and 12 months, 89% of DMEK and 73% of DSAEK grafts and 63% of DMEK and 64% of DSAEK grafts provided sufficient corneal deturgescence, respectively, represented by improvement in best-corrected visual acuity. DMEK group median preoperative Logarithm of the Minimum Angle of Resolution visual acuity of 1 increased to 0.5 after 6 and 12 months. DSAEK group median Logarithm of the Minimum Angle of Resolution visual acuity increased from 3 to 2 and 1.3 after 6 and 12 months. After 12 months, graft endothelial cell density had decreased by 58% in the DMEK group and by 59% in the DSAEK group. The proportion of patients requiring a rebubbling were 63% in the DMEK and 64% in the DSAEK group. No lamellar graft rejection occurred in either trial arm.

CONCLUSIONS

Both DMEK and DSAEK significantly improved visual acuity in patients after PK. Lamellar graft survival, loss of endothelial cells, and mean rebubbling rates were similar in both groups.

Ink Retention and Endothelial Cell Viability After the Application of an Orientation Stamp Over an Air Bubble During Descemet Membrane Endothelial Keratoplasty Graft Preparation

PURPOSE

To investigate stamp visibility and endothelial cell loss (ECL) after the application of an orientation mark to Descemet membrane endothelial keratoplasty (DMEK) grafts supported by an air bubble.

METHODS

Eighteen DMEK grafts were prepared at an eye bank using a technique where an orientation mark was applied to the stromal surface of a DMEK graft that was supported by a small air bubble placed at the edge of the 2 endothelial surfaces of the graft. Grafts were evaluated at 2 and 5 days for stamp visibility and at 5 days with calcein-AM staining for ECL. Nine grafts underwent cross-country shipping, and the ECL of shipped and nonshipped grafts was compared using unpaired t test.

RESULTS

All 18 DMEK grafts exhibited a single, solid, readily visible orientation mark 2 and 5 days after preparation with a mean ECL of 13.5% ± 4.9%. Shipping conditions had no effect on stain retention or ECL.

CONCLUSIONS

The application of an orientation stamp to a DMEK graft over an air bubble in an eye bank setting results in a single, solid orientation mark that is readily visible within the period in which most eye bank-prepared tissue is used. This technique produces no further ECL compared with the methods where the orientation stamp is applied through a stromal window. Eye bank technicians and surgeons can be confident that this modified preparation technique results in transplant-quality DMEK grafts with the additional benefit of conserving the stromal cap for use in other anterior lamellar procedures, thereby making efficient use of donor tissue.

A Novel Marking Technique for Descemet Membrane Endothelial Graft Using an Ophthalmic Viscoelastic Device

PURPOSE

To describe the viscoelastic marking technique, a novel marking technique of Descemet membrane endothelial keratoplasty (DMEK) grafts that enables usage of a single donor cornea for 2 surgeries-one that uses Descemet membrane and endothelium (DMEK) and the other using the stroma and Bowman layer.

METHODS

A retrospective case analysis was performed on 26 eyes of 26 consecutive patients who underwent DMEK using the "viscoelastic marking technique." In this novel technique, an ophthalmic viscoelastic device (Healon 5) is placed over the endothelial side. Descemet membrane is then folded in half over the ophthalmic viscoelastic device with the stromal side up, and the F mark is drawn on the stromal side of the folded Descemet membrane. Primary outcome was best spectacle-corrected visual acuity, and secondary outcomes included graft detachment and rebubble rate, graft failure, and endothelial cell density.

RESULTS

Mean best spectacle-corrected visual acuity improved significantly from 1.0 ± 0.7 logarithm of the minimum angle of resolution (LogMAR) before the surgery to 0.9 ± 0.7 LogMAR, 0.5 ± 0.6 LogMAR, 0.4 ± 0.2 LogMAR, and 0.4 ± 0.4 LogMAR at 1, 3, 6, and 12 months after surgery, respectively. Seven eyes (27%) had partial graft detachment that required air injection. Primary failure occurred in 3 eyes (11%). There were no free-floating donors or recognized inverted donors. The endothelial cell density loss at 12 months after surgery was a cell-loss rate of 38.3%.

CONCLUSIONS

The viscoelastic marking technique is a simple, approachable, and safe technique for marking DMEK grafts while preserving the anterior cornea for additional surgery.