Update on Descemet membrane endothelial keratoplasty.

PURPOSE OF REVIEW: To provide an update on new perspectives on Descemet membrane endothelial keratoplasty (DMEK). RECENT FINDINGS: Preloaded DMEK grafts allow optimization of DMEK surgery time and reduce costs of the procedure, which is allowing the procedure to become more easily performed as reflected in the increasing number of cases. The surgical technique in the United States differs from the technique in Europe, but outcomes have been similar. Hemi-DMEK and quarter-DMEK have shown similar outcomes to conventional DMEK with respect to corneal transparency and visual acuity. Three-year follow-up of hemi-DMEK has also shown stability in endothelial cell count while maintaining corneal transparency. SUMMARY: DMEK is becoming more accepted as the procedure of choice for treating endothelial failure. However, challenges with the surgical technique have limited wider implementation of this lamellar corneal transplantation. Preloaded DMEK provides one solution for the surgical challenges associated with the procedure while also reducing costs. Variations in the surgical technique for DMEK, including hemi-DMEK and quarter-DMEK, allow for central corneal clarity similar to traditional DMEK, but both result in lower endothelial cell density (ECD).

Human placenta aneurysm model for training neurosurgeons in vascular microsurgery.

BACKGROUND: Neurosurgery, a demanding specialty, involves many microsurgical procedures that require complex skills, including open surgical treatment of intracranial aneurysms. Simulation or practice models may be useful for acquiring these skills before trainees perform surgery on human patients. OBJECTIVE: To describe a human placenta model for the creation and clipping of aneurysms. METHODS: Placental vessels from 40 human placentas that were dimensionally comparable to the sizes of appropriate cerebral vessels were isolated to create aneurysms of different shapes. The placentas were then prepared for vascular microsurgery exercises. Sylvian fissure--like dissection technique and clipping of large- and small-necked aneurysms were practiced on human placentas with and without pulsatile flow. A surgical field designed to resemble a real craniotomy was reproduced in the model. RESULTS: The human placenta has a plethora of vessels that are of the proper dimensions to allow the creation of aneurysms with dome and neck dimensions similar to those of human saccular and fusiform cerebral aneurysms. These anatomic scenarios allowed aneurysm inspection, manipulation, and clipping practice. Technical microsurgical procedures include simulation of sylvian fissure dissection, unruptured aneurysm clipping, ruptured aneurysm clipping, and wrapping; all were reproduced with high fidelity to the haptics of live human surgery. Skill-training exercises realistically reproduced aneurysm clipping. CONCLUSION: Human placenta provides an inexpensive, widely available, convenient biological tissue that can be used to create models of cerebral aneurysms of different morphologies. Neurosurgical trainees may benefit from the preoperative use of a realistic model to gain familiarity and practice with critical surgical techniques for treating aneurysms.