Endothelium-in hydrodissection (Muraine) versus endothelium-out stripping graft preparation for Descemet Membrane Endothelial Keratoplasty: a prospective two-centre cohort study
This prospective two-centre cohort study found that while the Muraine endothelium-in hydrodissection technique for DMEK offers faster graft unfolding and equivalent early visual and endothelial outcomes compared to the standard endothelium-out method, it is associated with longer dissection times, higher rates of partial tissue loss, increased 6-month endothelial cell loss, and a significantly greater need for rebubbling due to air-only tamponade.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The human eye relies on a clear window at the front called the cornea to focus light and create sharp vision. Behind this window lies a delicate layer of cells known as the endothelium, which acts like a microscopic pump, constantly pushing fluid out of the cornea to keep it transparent. When these cells die or stop working due to disease or injury, the cornea swells with fluid, becoming cloudy and painful, a condition that can lead to blindness. For decades, the solution was to replace the entire cornea, but modern surgery has refined this process to replace only the damaged inner layer. This procedure, called Descemet membrane endothelial keratoplasty, involves peeling away the sick tissue and gluing a thin, healthy sheet of donor cells onto the back of the eye. The success of this surgery depends entirely on how well the surgeon can prepare that tiny, fragile sheet of tissue and get it to stick flat against the eye without damaging the precious cells.
In the operating room, surgeons face a tricky choice when preparing this donor tissue. They can peel the layer off so that the living cells face outward, like the skin of a fruit, or they can fold it so the cells face inward, tucked safely inside a roll. For years, the outward-facing method was the standard, but a newer technique emerged that folds the tissue inward using water pressure to separate the layers, hoping to protect the cells and make the surgery smoother. Researchers in Spain set out to test whether this newer, inward-facing approach was truly better than the traditional method in real-world hospital settings. They followed two groups of patients who had lost their corneal clarity, comparing those who received the traditional graft against those who received the folded, inward-facing graft. The goal was to see if the new method saved more cells, restored vision faster, or caused fewer complications.
The study involved surgeons at two different hospitals, each sticking to their preferred method. One team used the traditional technique on twenty-seven eyes, while the other team used the newer water-pressure method on forty-two eyes. Both groups of patients had already undergone cataract surgery in the past, and all were suffering from corneal swelling. The researchers carefully measured how many cells survived the surgery, how quickly patients could see again, and how often the grafts needed to be re-attached. They also timed the surgery, noting how long it took to prepare the tissue and how long it took for the graft to unfold and settle inside the eye.
The results showed that both methods worked well in the short term. One month after surgery, the number of surviving cells and the clarity of vision were nearly identical between the two groups. Patients in both groups saw significant improvement, and the grafts held up well initially. However, as time passed, a clear difference emerged. In the group that received the traditional graft, the number of cells remained stable after the first month. In contrast, the group with the inward-facing grafts continued to lose cells over the next five months. By six months, the inward-facing group had lost significantly more cells than the traditional group, dropping to a level that was nearly sixteen percent lower, though the difference in absolute numbers was not statistically significant.
The way the surgery was performed also revealed distinct trade-offs. The newer, inward-facing technique took longer to prepare the tissue, adding an average of twelve and a half minutes to the dissection phase. However, once the tissue was inside the eye, it unfolded more quickly and predictably, especially in eyes that had not suffered complications during previous cataract surgery. Despite this speed advantage during the unfolding phase, the newer method came with a higher risk of tearing the delicate tissue during preparation. In about twenty-six percent of the cases using the inward-facing method, a small piece of the graft was lost during the process, though surgeons were still able to implant the remaining tissue in every single case.
The most striking difference appeared in the need for follow-up procedures. In the traditional group, not a single patient needed a second injection of air to re-attach the graft. In the inward-facing group, nearly half of the patients required a second surgery to push the graft back into place. The researchers found that this high rate of re-attachment was largely due to the type of gas used to hold the graft in place. The traditional group received a specific gas mixture that lasted longer, while many in the newer group received only air, which dissipated quickly. When the gas bubble disappeared, the graft often detached, requiring a return to the operating room. Additionally, the newer technique saw more cases of partial tissue loss and a higher rate of re-attachment, suggesting that the way the tissue was handled and the type of gas used played a bigger role than the direction the cells were facing.
Ultimately, the study concluded that while the inward-facing technique offers a faster unfolding process and equivalent vision results in the first month, it carries a higher risk of tissue loss and a much greater need for re-attachment surgeries. The researchers noted that these issues were not necessarily caused by the direction the cells faced, but rather by the specific choices made during the surgery, such as using only air instead of a longer-lasting gas. They suggested that if surgeons choose to use this newer method, they should adopt specific protocols, such as using a longer-lasting gas and taking extra steps to prevent pressure buildup, to match the safety and stability of the traditional approach. The findings highlight that in the delicate world of corneal surgery, the tools and techniques used to hold the graft in place may matter just as much as the method used to prepare it.
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