This article is more than 5 years old. Information may no longer be current.
Performing DMEK in the presence of an open-loop anterior chamber IOL
OSN Surgical Maneuvers Editor, Thomas “TJ” John, MD, provides surgical pearls for this procedure.
Click Here to Manage Email Alerts
Corneal transplantation for endothelial decompensation has moved rapidly away from full-thickness penetrating keratoplasty and toward endothelial keratoplasty, which offers premium transplantation techniques by which corneal circular wounds and sutures to hold the corneal graft are eliminated. An added bonus of endothelial keratoplasty is the elimination of iatrogenically induced corneal astigmatism, which often requires contact lens fitting for visual rehabilitation.
Descemet’s stripping endothelial keratoplasty is the surgery that is performed by the majority of corneal surgeons. The gap between DSEK and Descemet’s membrane endothelial keratoplasty surgery is the incremental learning curve of handling non-stromal, delicate, highly flexible tissue within the anterior chamber and the added challenge of harvesting the donor Descemet’s membrane in DMEK. However, the final outcome of DMEK appears to be somewhat superior to DSEK in terms of better visual outcomes and lower rates of corneal graft rejection. The interest in DMEK continues to rise among corneal surgeons.
Currently, various attempts are being made to make DMEK surgery less complex and within the reach of the corneal surgeon’s comfort zone. This requires significant simplification of the DMEK surgical procedure, introduction of new surgical instrumentation and lowering the bar of complexity to match the surgical skill set of the majority of corneal surgeons.
I suspect this conversion from DSEK to DMEK will continue in the near future, as newer instrumentation and simplification of the procedure take place. Further, tissue preparation by eye banks can remove the surgeon’s task of harvesting the Descemet’s membrane in the operating room. All of these and other developments in this arena of newer corneal transplantation techniques will ultimately benefit our patients with quicker surgical recovery and better quality of vision after corneal endothelial replacement surgery.
There is some added complexity to a DMEK procedure in the presence of a space-occupying anterior chamber IOL. In this column, the technique of DMEK surgery in the presence of an open-loop anterior chamber IOL is described, and some surgical pearls are provided.
Surgical technique
The surgical procedure is performed under monitored anesthesia care, along with supplemental topical 2% lidocaine jelly applied to the ocular surface at the beginning of the procedure. A temporal approach is elected.
When the corneal epithelium is edematous (Figure 1), it compromises the view of the anterior chamber and the anterior segment of the eye. If this visual degradation were interfering with proper visualization of the anterior segment, one option would be to gently remove the epithelium, leaving an intact, undamaged Bowman’s layer. In this case, the open-loop anterior chamber IOL and a pre-existing, large peripheral iridectomy are visible through the cloudy cornea (Figure 1). The open-loop anterior chamber IOL is stable, with the haptics anchored with focal, fibrous tissue (Figure 1).
Figure 1. Broad (left) and slit beam (right) views of pseudophakic bullous keratopathy with diffuse corneal stromal and epithelial edema with irregular epithelial surface and scattered light reflex on the central corneal surface. Also seen is an open-loop anterior chamber IOL that is in a stable position and a large peripheral iridectomy.
Images: John T
Figure 2. An 8-mm circular mark is made on the corneal surface and serves as a guide for descemetorrhexis.
Figure 3. Surgeon’s view from a temporal approach showing descemetorrhexis and complete detachment of the patient’s Descemet’s membrane using the John Dexatome spatula, taking care not to contact the anterior chamber IOL. The unique curvature of the John Dexatome spatula is well suited for removal of the patient’s central Descemet’s membrane.
Figure 4. After scoring, the cut edge of the Descemet’s membrane is lifted using the John DMEK Separator.
Figure 5. Descemet’s membrane is lifted using the John DMEK Lifting Forceps.
An 8-mm diameter circular mark is made on the corneal surface, which will serve as a guide for the descemetorrhexis (Figure 2). Descemetorrhexis is carried out using the John Dexatome DMEK/DSAEK Spatula (ASICO), and the central Descemet’s membrane is removed as a single disc (Figure 3). The unique curvature of the Dexatome spatula is specially suited for this segment of DMEK surgery (Figure 3).
Attention is then directed to the donor cornea. The donor cornea is scored 360° on a John DMEK Base (Storz, Bausch + Lomb) using the John DMEK Scroller (Storz, Bausch + Lomb), and the cut edge of the Descemet’s membrane is gently lifted using the John DMEK Separator (Storz, Bausch + Lomb; Figure 4), thus initiating the separation of the donor Descemet’s membrane from the inner surface of the donor corneal stroma. After this initial separation, the donor Descemet’s membrane is then progressively lifted toward the central cornea (Figure 5), taking care not to tear the Descemet’s membrane.
After partial trephination of the donor cornea from the endothelial side using a disposable trephine, the Descemet’s membrane is progressively detached until the entire Descemet’s membrane, with a diameter of 8 mm, is removed (Figure 6). The Descemet’s membrane is then stained with trypan blue (Figure 7) in the right well of a John DMEK Cutting Block (Storz, Bausch + Lomb) and introduced into the recipient anterior chamber (Figure 7). Gentle fluid irrigation partially opens Descemet’s scroll (Figure 8).
The intraoperative slit-lamp examination reveals the limited space within the anterior chamber due to the presence of an anterior chamber IOL (Figure 8). It is important to center the Descemet’s membrane within the circular mark, as shown in Figure 8. The pyramid sign (Figure 8) is a welcome sign, as further unfolding of Descemet’s membrane is usually less cumbersome. The John DMEK Smoother (Storz, Bausch + Lomb; Figure 9) has a highly polished sphere at the terminal end, which facilitates proper centration of the Descemet’s membrane and permits unrolling of the Descemet’s membrane without the use of any small air bubble within the anterior chamber (Figure 9). This is especially useful in the presence of an anterior chamber IOL.
Figure 6. Descemet’s membrane is then peeled off as a single post-trephination disc from the donor cornea using the John DMEK Lifting Forceps.
Figure 7. Donor Descemet’s membrane is stained with trypan blue (left) and then introduced into the recipient anterior chamber (right).
Figure 8. Sterile balanced salt solution is used to gently open Descemet’s membrane scoll (left), and the slit beam shows the limited space within the anterior chamber due to the presence of the anterior chamber IOL (right).
Figure 9. Using the John DMEK Smoother, the donor Descemet’s membrane scroll is gently unrolled.
Figure 10. Donor Descemet’s membrane is then attached to the recipient cornea with an air bubble. The slit view shows the uniform attachment of the donor Descemet’s membrane to the recipient cornea and the clear space between the cornea and the anterior chamber IOL.
Figure 10 shows the endpoint of this procedure with a uniformly attached donor Descemet’s membrane that is properly centered within the circular mark on the corneal surface. The slit beam (Figure 10) confirms uniform Descemet’s membrane attachment without any folds. The anterior chamber IOL is clearly visible in Figure 10.
Surgical pearls
- It is important to be cognizant of the limited space in the anterior chamber with the presence of an anterior chamber IOL. Hence, all unfolding attempts need to be gentle, keeping the Descemet’s membrane within the confined space between the anterior surface of the anterior chamber IOL and the inner surface of the patient’s cornea at all times.
- Avoid any aggressive fluid irrigation that would flush the Descemet’s membrane into areas such as the region between the anterior chamber IOL and the iris, or into the pupillary space.
- Gentle corneal surface massage and nudging motions with the John DMEK Smoother greatly facilitate the unfolding of the Descemet’s membrane in its resting position.
- Before the final air injection, ensure that the tip of the cannula is positioned centrally between the anterior chamber IOL anterior surface and the cornea and not between the anterior chamber IOL and the iris.
- Take care not to move the anterior chamber IOL with the tip of the cannula.
- Final air injection should be slow and steady, avoiding any sudden bursts of air that could dislodge and push the Descemet’s membrane into the peripheral space of the anterior chamber.
- Ensure uniform attachment of a well-centered Descemet’s membrane using an intraoperative slit lamp when available.
- Ascertain adequate pupillary dilation and peripheral iridectomy.