1. Hemi-DMEK Transplantation: Novel Method to Increase the Pool of Endothelial Graft Tissue Lam FC 1-4, Baydoun L 2-4, Dirisamer M 2-4, Lie J 2-4, Dapena I 2-4 and Melles GRJ 2-4 1- Netherlands Institute for Innovative Ocular Surgery (NIIOS), 2- Melles Cornea Clinic (MHR), 3- Amnitrans Eye Bank (AER), Rotterdam, The Netherlands, 4- Western Sussex NHS Foundation Trust Author 6 is a consultant for D.O.R.C International/Dutch Ophthalmic USA. Author 1, 2, 3, 4, and 5 have no financial interest in the subject matter of this poster

2. Background Current preparation techniques aim to harvest central part of Descemet membrane & endothelium (8.5-9.5mm) The peripheral rim, i.e. about 1/2 of the graft surface area, is discarded Demand for corneal endothelial grafts is increasing, while there is still a significant shortage of donor corneal tissue 1

3. The Concept The Descemet membrane graft is very thin, for DMEK there is no optical or technical reason to only utilize the central portion of the donor tissue in contrast to PK and DSEK/DSAEK By reducing wastage, there is enough endothelial tissue to provide 2 DMEK grafts from a single donor cornea (the circle with dashed lines represent a standard 9.5mm diameter DMEK for comparison)

4. Aim, Materials & Methods Aim To describe the feasibility of harvesting and transplanting a half-moon shaped ´Hemi-DMEK´ graft with its outcomes up to 6 months Study Design Prospective case series study 3 pseudophakic eyes with corneal decompensation (Fuchs endothelial dystrophy). Ages: 66, 72, 75 years. All female. One amblyopic Outcome Measures Best Corrected Visual Acuity Endothelial Cell Density (ECD) Complications

5. Methods: Hemi-DMEK graft preparation 1. DM loosened from the scleral spur 2. Corneoscleral button divided into 2 equal halves 3. DM completely stripped off from posterior stroma 4. DM roll forms after immersion in saline

6. Methods: Hemi-DMEK Surgery Previously described standard DMEK techniques 2,3 were used with adjustments 9mm circular Descemetorhexis Centering done with the longer graft dimension placed eccentrically Air bubble injected underneath the graft & anterior chamber air fill for 60 min

7. Results Hemi-DMEK was uneventful in all cases All 3 grafts were fully attached except for a small persistent peripheral detachment in Case 1 (orange arrows). No re-bubbling was required Corneal clarity and best corrected visual acuity improved in all cases Due to the difference in shape between the semicircular DMEK graft & the circular DM-rhexis, areas of bare stroma were present in all cases (Figure 1, middle column)

8. Results Areas where the hemi-DMEK graft was situated were the first areas of cornea to clear The bare corneal stromal areas adjacent to the hemi-DMEK grafts and the corneal periphery were initially edematous However, these areas cleared starting from the area of the graft spreading outwards to the bare stromal areas and then to the peripheral cornea (Figure 2, left to right)

9. Results Most of the ECD decrease after hemi-DMEK was by one month. ECD decrease thereafter were smaller. In contrast, the average ECD decrease after standard DMEK is 30-35% at 6 months postop followed by yearly decrease of 7%. 4

10. Results This difference in the ECD decrease may be due to a different migratory pattern in hemi- DMEK with endothelial cells having migrated from the graft (Left) to previously denuded bare stromal area (right) Figure 3: Postop. Specular microscopy images: Case 3 at 6 months Central Previously bare stroma – previously devoid of cells

11. Conclusion Hemi-DMEK (half-moon) graft preparation and surgery was technically feasible with slight modifications to standard technique for DMEK surgery Hemi-DMEK may mimic visual outcomes of standard (full- moon) DMEK If so, hemi-DMEK may have the potential to double the availability of donor endothelial tissue for DMEK Await larger series with outcomes on allograft rejection and graft survival

12. References 1.Gaum L, Reynold I, Jones MN et al. Tissue and corneal donation & transplantation in the UK. Br J Anaesth. 2012;10:i43-i47. 2.Dapena I, Moutsouris K, Droutsas K et al. Standardized Standardized “No-Touch” Technique for DMEK: Arch Ophthalmol. 2011;129(1):88-94. 3.Liarakos V, Dapena I, Ham L et.al. Intraocular graft unfolding techniques in DMEK. JAMA Ophthalmol. 2013 Jan;131(1):29-35. 4.Baydoun L, Tong CM, Tse WW et al. ECD after DMEK: 1-5-Year Follow-up. AJO 2012;154(4):762- 3.