Preserving the lens important in young phakic patients undergoing DMEK
A step-by-step guide details the procedure, and surgical pearls help to ensure a successful outcome.
Endothelial keratoplasty, or EK, appears to be the epicenter of the corneal transplantation scene, and it has surpassed penetrating keratoplasty for the surgical correction of endothelial decompensation and corneal edema in the United States. This preferred choice of EK over PK is largely due to the superior quality of vision that returns relatively quickly after EK surgery and the lowest endothelial rejection rate as compared with other forms of corneal transplantation; in addition, the majority of the patient’s own cornea is retained without any full-thickness corneal wound, and the use of conventional sutures, for the most part, is eliminated in EK.
All three segments of ophthalmic surgical care — the patient, the corneal surgeon and industry — have seemed to contribute in a positive way to make EK prominent in the corneal transplantation arena. The patient wishes for a better quality of vision to match an active lifestyle; the surgeon seeks an improved surgical procedure; and industry develops new EK instruments to facilitate the transition from full-thickness surgery to selective tissue corneal transplantation. In addition, eye banks have embraced EK procedures and are providing ready-to-use EK donor tissues for corneal surgeons. These efforts from all sides have helped EK move to the preferred procedure of choice when dealing with endothelial decompensation and corneal edema with or without associated Fuchs’ corneal dystrophy.
Although, most EK procedures are usually performed in the pseudophakic eye, there is a subset of patients with Fuchs’ dystrophy who are phakic with a clear lens and are symptomatic due to endothelial decompensation and require an EK procedure for their visual rehabilitation. Because these patients are young, preservation of the lens and useful accommodation becomes an important factor, and phakic Descemet’s membrane endothelial keratoplasty needs to be considered. It is, however, important to inform the patient about the possibility of lens removal and IOL implantation if there is intraoperative lens damage or postoperative lens clouding.
In this column, I describe the surgical technique of DMEK in a phakic eye and point out some of the surgical pearls to keep in mind while performing this procedure.
Viewing the anterior chamber through a cloudy cornea can be a challenge in this phakic eye with Fuchs’ corneal dystrophy and endothelial decompensation that is more pronounced in the central region (Figure 1). Removing the surface corneal epithelium will help improve visualization of the anterior chamber, and this can be achieved by using a dry Weck-Cel spear, followed by the use of smooth non-toothed forceps and curved Vannas scissors to remove most of the epithelium, except for the most peripheral epithelium (Figure 1). This helps retain corneal stem cells.
Next, using the John DMEK marker (ASICO), an 8-mm circular mark is made on the surface of the de-epithelialized cornea (Figure 2). This provides a guide mark for the descemetorrhexis. The anterior chamber is entered via a stab incision using a 15° super blade close to the limbus via the clear cornea, and Miostat (carbachol, Alcon) is injected to further constrict the pupil to afford lens protection. Healon (sodium hyaluronate, Abbott Medical Optics) is then injected to fill the anterior chamber. The John DMEK Dexatome (Bausch + Lomb) is used to perform the descemetorrhexis without damaging the patient’s corneal stroma (Figure 2). The Dexatome is largely used over the anterior iris surface, thus avoiding any potential damage to the crystalline lens (Figure 2). Initially, a 180° descemetorrhexis is performed in a counterclockwise direction (Figure 2), followed by a second 180° descemetorrhexis in a clockwise fashion to complete the circular descemetorrhexis.
Descemet’s membrane is detached as a single disc without causing any iatrogenic corneal stromal damage by making all contact with the folded Descemet’s membrane and not the exposed inner corneal stroma. The detached Descemet’s membrane is removed as a single disc (Figure 2). The tip of the Healon cannula is introduced into the anterior chamber via a temporal clear corneal incision and gently placed between the anterior lens capsule and the posterior iris surface through the pupil, and Healon is gently injected to anteriorly raise the iris away from the lens surface (Figure 3).
Next, an inferior peripheral iridectomy is performed using micro scissors, avoiding any damage to the crystalline lens (Figure 3). A plastic soft-tipped irrigation and aspiration unit (Bausch + Lomb) is used to aspirate and remove all Healon from the anterior chamber and from behind the iris (Figure 4). The soft tip is less traumatic compared with a metal tip, which is well suited to rub and scrub the inner corneal stromal surface (Figure 4).
The trypan blue-stained donor Descemet’s membrane with healthy donor endothelial cells is introduced into the recipient anterior chamber (Figure 5). Using a 30-gauge blunt-tipped cannula, sterile balanced salt solution is injected into the anterior chamber to partially unroll the donor Descemet’s membrane (Figure 5). An intraoperative slit lamp view helps identify the donor Descemet’s membrane orientation (Figure 6). This is repeated as needed during the surgical procedure until the Descemet’s membrane is fully unrolled and attached. Fluidics helps unroll the donor Descemet’s membrane within the patient’s anterior chamber (Figure 7).
The John DMEK Smoother (Bausch + Lomb) (Figure 8) is an extremely useful DMEK instrument for both unrolling the Descemet’s membrane and moving the Descemet’s membrane in any desired direction for proper centration and attachment to the recipient inner corneal surface. The John DMEK Smoother is used to progressively unroll the donor Descemet’s membrane within the patient’s anterior chamber (Figure 9), and it is used to move the donor Descemet’s membrane to match the circular mark on the anterior corneal surface for the final resting position (Figure 10) with perfect centration of the donor Descemet’s membrane to the recipient cornea. A blunt cannula is introduced into the anterior chamber, and air is gently and steadily injected to fill the anterior chamber (Figure 11). A muscle hook is used to iron the anterior corneal surface to ensure uniform attachment of the donor Descemet’s membrane to the recipient cornea against the air bubble support (Figure 11).
Figure 12 displays the completed view of the DMEK procedure in this phakic eye. Intraoperative slit lamp examination helps confirm uniform attachment of the donor Descemet’s membrane to the patient’s cornea without any interface debris or air bubble (Figure 12).
1. The primary difference in this case compared with others is the presence of a crystalline lens. Every step should be taken to protect the lens and not cause any iatrogenic damage to the lens.
2. Pupillary constriction using Miostat helps provide significant lens protection.
3. Fill the anterior chamber to the maximum with Healon, thus providing adequate space within the anterior chamber to complete the required surgical procedures without causing any lens damage.
4. Introduce instruments over the iris surface off-center and work in areas away from the pupillary region.
5. Use a soft-tip plastic I&A unit and avoid a metal I&A unit if possible to provide added safety during the procedure.
6. Raise the iris away from the anterior lens surface before performing surgical inferior peripheral iridectomy.
7. DMEK instruments help simplify the procedure. The DMEK Dexatome curvature is well suited to work in any region of the inner corneal surface. This is surgically superior to any straight instrument to work on the inner concave surface of the patient’s cornea.
8. The DMEK Smoother helps in both unrolling the donor Descemet’s membrane and easily centering the Descemet’s membrane disc to the recipient cornea.
9. Use an intraoperative slit lamp, if available, for both Descemet’s membrane orientation and also to evaluate the donor-recipient interface.
- Burkhart ZN, et al. J Cataract Refract Surg. 2014;doi:10.1016/j.jcrs.2013.08.047.
- John T, ed. Endothelial Transplant, DSAEK, DMEK, & DLEK. Panama City, Panama: Jaypee-Highlights Medical Publishers; 2010.
- John T, ed. Surgical Techniques in Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006.
- John T, ed. Lamellar Corneal Surgery. New York: McGraw-Hill Companies; 2008.
- Rodríguez-Calvo-de-Mora M, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2014.09.004.
- For more information:
- Thomas “TJ” John, MD, is a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at email: email@example.com.
Disclosure: John reports he is a consultant to ASICO and Bausch + Lomb.