A single-use, disposable device implants donor allograft tissue during endothelial keratoplasty.
Corneal endothelial failure is a common cause of corneal transplants. According to the Eye Bank Association of America, transplant tissue distributed for endothelial keratoplasty accounted for 18,221 (43%) of all keratoplasties performed in the US during 2009. Fuchs dystrophy, “other” causes, and post-cataract surgery edema were identified as the leading indications for endothelial replacement surgery. The leading indicator, Fuchs endothelial dystrophy, is an inheritable genetic condition that results in loss of endothelial cells and formation of an abnormal extracellular matrix.
Beginning in 2005, selective endothelial replacement gained momentum as the treatment of choice for endothelial pathologies. While a successful surgery, penetrating keratoplasty for primarily endothelial failure removes a significant amount of otherwise normal corneal tissue. Risk factors, including challenging intraoperative events, can complicate penetrating keratoplasties and unpredictable postoperative astigmatism may compromise outcomes and patient satisfaction. Allogenic graft rejection is more common in penetrating than endothelial keratoplasties.
Endothelial keratoplasty is the targeted removal of pathologic host endothelium and Descemet membrane, and replacement with a donor allograft consisting of a stroma-Descemet-endothelium complex created manually or using microkeratome dissection. The donor posterior “button” is trephined in the operating room to fit the recipient bed, most often from 7.5–9 mm in diameter. Thickness of the donor allograft varies, and one study has demonstrated better postoperative visual acuity occurs when tissue thickness is less than or equal to 131 μm. After the donor posterior lamella is coated with a small amount of cohesive ophthalmic viscoelastic, it is separated from the anterior cap, 60-40 folded, and inserted with forceps into the anterior chamber. The forceps are opened and gently removed from the anterior chamber while carefully avoiding damage to the graft endothelium or changing its stroma-to-stroma orientation. Once the graft is unfolded and positioned near the posterior stroma, an air bubble is injected to affix the donor tissue to the host. After a short time, the bubble is partially drained and the patient is assessed for adequate graft attachment. In most cases, the graft adheres to the host and the remaining air bubble resorbs in a few days. The pump action of the healthy donor endothelium begins to restore corneal transparency. The critical techniques are inserting the donor button while maintaining endothelial integrity, controlling graft position, and central deployment.
Existing techniques for inserting the donor endothelium can be divided into several categories: forceps; pullthrough; and, custom-device assisted delivery methods. Single-point fixation forceps attempt to minimize creasing and compression force along the length of the blades. When the forceps are closed the tips coapt, and the blades remain slightly separated while securing the folded tissue. Forceps insertion does not protect tissue from compressing during passage through the wound.
Pull-through techniques use a “guide” that holds folded or unfolded tissue, depending on which device is used. Trephined donor tissue is loaded on the guide and placed at the wound to hold it agape. Through a second wound, opposite from the first, specialized long-arm forceps are inserted across the anterior chamber and used to pull the graft into position.
In many instances, donor tissue is passed through a 5-mm wound, which has been shown to cause less postoperative endothelial cell loss than smaller wounds. Forceps and pull-through guides can be used with wounds sized approximately from 3–5 mm. While smaller incisions provide more anterior chamber stability, less iris prolapse, and less astigmatism than 5-mm incisions, they result in significant donor endothelial damage. A vital dye study demonstrated that smaller wound size contributed to decreased endothelial cell density when using either forceps or pull-through techniques. These techniques, while technically challenging, have contributed to the successful advancement of endothelial keratoplasty.
The EndoSerter™ is a single-use, disposable device used to efficiently and precisely implant donor allograft tissue during endothelial keratoplasty. It is designed to carry graft tissue equal to or less than 175 μm thick, and 8.5 mm or less in diameter. The patented tissue loading and deployment system gently retracts the graft with minimal manipulation into the insertion sheath, and then deploys it through a 4-mm wound without plunging, pulling, or folding. Tissue is deployed in the anterior chamber by putting the tip of the insertion sheath at the far edge of the recipient bed, then moving the EndoSerter finger control to uncover the graft. As the graft is gently deployed, the surgeon controls its precise placement without any instrument interference. Accurate placement occurs as the insertion sheath withdraws back through the wound, centering the graft in the bed. The luer connection allows irrigation through the device to control chamber depth.
The EndoSerter is capable of a small incision clear cornea surgery that requires no additional instrumentation. Advantages of topical EndoSerter endothelial keratoplasty include a smaller wound and no needle for retrobulbar block, thereby eliminating risk of hemorrhage or globe perforation. Efficiency and cost saving are accomplished because there is no need for sutures, conjunctival incision, or cautery. Accordingly, this results in reduced surgical risks and decreased operating room when compared to the costs required for forceps insertion. The device simplifies the surgical procedure, accurately delivers and places tissue through a small wound, and offers integral irrigation to maintain a deep chamber.
This technology was done by Ocular Systems, Winston-Salem, NC. For more information, visit http://info.hotims.com/34453-197.