corneal diseases

Surgeons weigh merits of transplant techniques for unstable corneas

Welcome to another edition of CEDARS/ASPENS Debates. CEDARS/ASPENS is a society of cornea, cataract and refractive surgery specialists, here to discuss some of the latest hot topics in ophthalmology.

Kenneth A. Beckman, MD, FACS
Kenneth A. Beckman

This month, W. Barry Lee, MD, FACS, shares his experience using deep anterior lamellar keratoplasty in patients with unstable corneas, while Jack S. Parker, MD, PhD, discusses the benefits of Bowman’s layer onlay in patients with post-RK ectasia. We hope you enjoy the discussion.

Kenneth A. Beckman, MD, FACS


Deep anterior lamellar keratoplasty has seen a resurgence in the new millennium. The most common indication is keratoconus and corneal ectasia, in addition to stromal corneal dystrophies and corneal scars following infections or trauma. In essence, any corneal condition with normal endothelium and diseased stroma in the setting of poor best corrected vision with spectacles or contact lenses remains a good candidate for DALK.

W. Barry Lee, MD, FACS
W. Barry Lee

In the mid-20th century, DALK became a popular technique to use over penetrating keratoplasty grafts given the higher rate of failure with PK without microsurgical instruments, fine sutures and lack of anti-rejection medications. The challenge remained vision reduction from interface scarring and haze given the absence of lasers and appropriate blades to make lamellar cuts, as well as a lack of instruments and techniques to remove all the stroma and leave bare Descemet’s membrane. DALK techniques were abandoned as PK took over with modern instrumentation, microscopes, technique standardization and anti-rejection medications. Procedures such as femtosecond laser-assisted DALK and Anwar’s big bubble DALK have afforded major advantages for DALK over PK. It also allows the use of tissue without excellent endothelium, a major advantage internationally or where eye banking systems are not as well developed as in the United States.

Adoption of DALK in the U.S. has been slower than international countries due to our well-developed eye banking system in which donor corneas with excellent endothelium remain abundant. Many corneal surgeons also find PK more efficient in the operating room compared with DALK, likely because of experience and training that favored PK. Having said that, the advantages of DALK over PK are the main reason I choose it as my primary procedure for unstable corneas with healthy endothelium.

Completely eliminating the risk for endothelial graft rejection and open sky suprachoroidal hemorrhages is the biggest advantage over PK. In addition, numerous publications have shown secondary potential advantages over PK, including less endothelial cell loss, quicker time to vision stability, quicker time to steroid discontinuation, and less risk for glaucoma, iris synechiae and cataract formation. The development of standardization with big bubble Descemet’s baring techniques, as well as abundant publications on outcomes and long-term complications, have made me prefer DALK over techniques such as Bowman’s layer transplantation, which currently lacks the volume of publications of DALK and long-term complication comparisons to DALK.

Given the abundance of cornea fellowship training programs, online surgical training videos and live courses in concert with the numerous advantages of DALK over PK, it baffles me as to why more surgeons do not use DALK over PK when appropriate. Weighing all the intraoperative and postoperative advantages of DALK in combination with the volume of peer-reviewed literature and the numerous opportunities to learn DALK, there is no reason to choose PK for diseased corneas that need surgery with healthy endothelium.

Bowman’s layer onlay

Bowman’s layer is regarded as one of the strongest parts of a native cornea and the layer of the cornea that has been identified as being pathological in some diseases in which the cornea is weak, for example, keratoconus. About 10 years ago, there was a brilliant Dutch ophthalmologist, Gerrit Melles, MD, PhD, who had the idea of performing a Bowman’s layer transplant to try to restore some of the mechanical strength of a keratoconic cornea. For years, he performed an operation called Bowman’s layer inlay. This is an operation in which a pocket is dissected within the keratoconic cornea. The Bowman’s layer graft is placed in the pocket, and the recipient cornea heals around that layer. This splints the recipient cornea and stabilizes and strengthens its shape. It also has the additional benefit of flattening the cornea.

Jack S. Parker, MD, PhD
Jack S. Parker

Since then, Melles has refined the technique to a modified version called Bowman’s layer onlay, in which the graft is placed on top of the cornea instead of within a pocket. Placing the graft on top of the cornea seems to be much easier and equally effective in corneas with mechanical strength limitations.

Bowman’s layer onlay was designed for patients who could not have the inlay or patients with corneal weakness from prior RK. If a patient had prior RK, the cornea is weak, flexible, flimsy and protruding. Melles figured out that placing the Bowman’s layer graft on top of the recipient cornea restores the mechanical strengths of the cornea, making it much less pathologically flexible. These patients with prior RK not only have warped corneas, but they have unstable corneas. The corneas flex in and out, and that makes the patient’s vision unstable. You cannot correct it with anything. However, with Bowman’s layer onlay, it basically becomes a static target. The cornea is no longer moving up and down. It assumes a fixed shape, which allows you to provide some refractive correction. Bowman’s layer onlay surgery has become a great thing for patients with post-RK ectasia.

Read the article on Healio.

Abandoning stamp can make DMEK better

S- or F-stamping donor tissue for Descemet’s membrane endothelial keratoplasty is widely practiced to guard against DMEK’s most embarrassing potential complication: accidental upside-down graft implantation.

These orientation marks are so common, in fact, that many DMEK surgeons have never even attempted the operation without them. However, the originally described DMEK technique was stamp-free, and that is still the way the operation is performed today at the Netherlands Institute for Innovative Ocular Surgery, where DMEK was invented. So, rather than a necessary feature, tissue stamps might be more appropriately regarded as “accessories,” with definite yet unmentioned drawbacks.

Figure 1. DMEK graft immediately after injection. Unfolding must initially proceed without use of the S-stamp. Figure 2. S-stamp only partially visible secondary to inadequate/overly tentative application. Figure 3. Anterior segment OCT sections 1 day after DMEK and corresponding slit lamp photos. In the superior cornea, the graft is well attached, and the overlying stroma is thin and clear. However, inferiorly in the location of the S-stamp, the stroma is edematous, suggesting local dysfunction of the graft/endothelium.

Admittedly, a certain emotional sense of security accompanies the use of stamped tissue. It feels like the safe thing to do. And if applied by the eye bank, it also requires no extra time, effort or expense. Finally, when not using stamps, the inevitable occurrence of an upside-down graft is so chastening and humiliating that it is enough to send any reasonable person searching for a “never again” solution.

But, in practice, the stamp is just not that useful. The DMEK graft is almost always injected as a scroll, then opened and manipulated, even before the stamp is remotely discernable (Figure 1). Consequently, the stamp has no role in the critical part of the surgery (unfolding the graft); it only offers a final check against mistakes. But even this function is often thwarted because, frequently, the stamp is only partially applied, such that half of the common “S” or “F” is missing, rendering it nearly impossible to read (Figure 2). The reason these stamps are often so poorly retained is that eye banks are typically tentative in applying them because the process (ie, stamping with a metallic instrument dipped in ink and alcohol) is unquestionably damaging, resulting in a circular swath of dead graft. These areas are additionally liable to local detachment and delayed corneal clearance (Figure 3), and the ink marks remain faintly visible for years after the surgery. As a result, the typical outcome is a poor stamp, useless for determining orientation but visible forever in the patient’s eye in a region of dead cells.

Jack S. Parker

It is also worth remembering that upside-down graft implantation is rare, occurring in fewer than 5% of operations, even without the use of tissue stamps and even during initial learning curves. So, because the potential benefit is (at most) one out of 20 cases, that means 19 out of 20 cases can only be harmed by the application of the stamp, which destroys cells every single time.

Finally, one of the most personally satisfying elements of DMEK is the beauty and elegance of the operation, which is partially spoiled by an unseemly purple tattoo. Abandoning the stamp might not make the operation easier, but it does make it better, and if DMEK surgeons did not care about that, then they would not have switched over from Descemet’s stripping automated endothelial keratoplasty in the first place.


Dirisamer M, et al. Am J Ophthalmol. 2011;doi:10.1016/j.ajo.2011.03.031.

Surgeon offers tips to avoid straight haptic during lens implantation

Ultrasert is the name of Alcon’s delivery system for its preloaded AcrySof IQ IOLs. These lenses arrive already packaged inside their injector and need only priming with viscoelastic before delivery.

Still, the process is not entirely foolproof, and some amount of technical skill is nevertheless required. One common problem is failure of the leading haptic to curl backward over the optic face. If so, it may exit the injector sticking straight out, twisted in the wrong direction. This misconfiguration may increase the difficulty and danger of lens implantation. Here, we describe, first, tips for lens priming to avoid the straight haptic and, second, a simple rescue maneuver that enables a straight haptic IOL to be safely injected regardless.

Ultrasert priming begins with injection of an ophthalmic viscosurgical device through the fill port in the front of the device. Then, the lens stop and plunger lock are removed, and the plunger is advanced. The trick for avoiding a straight haptic is simply to advance the plunger slowly (over the span of at least 7 seconds) in one smooth and continuous motion using the palm of the hand (Figure 1, Video 1). Slow forward advancement permits the haptic time to curl in the proper direction, and pushing with the palm avoids imparting any rotational twist to the plunger, which may be inadvertently administered when using a thumb. Going slow and palm pushing are enough to prevent 99% of straight haptics. For the remaining 1%, any blunt-tipped secondary instrument can be inserted into the mouth of the injector and gently used to tease the straight haptic back, over the optic face. This is easily done by a technician assistant and without the use of a microscope. As a result, the lens may be handed off to the surgeon properly curled, ready for injection, in virtually 100% of cases.

Nevertheless, if a surgeon should encounter a straight haptic, a simple modification to the standard lens insertion technique permits a normal delivery. After placement through the main wound, the injector should be rotated clockwise, so its bevel/nozzle opening faces to the left. Advance the plunger and inject the lens slowly, watching the leading haptic. Just before the optic exits, rotate the injector back (counterclockwise) into its normal position to complete lens delivery. This little trick of clockwise then counterclockwise rotation can compensate for the twisted geometry of the straight haptic and facilitate normal lens insertion even when the lens is misloaded.

An even simpler, if less elegant, compensatory technique is to initially deliver the IOL into the anterior chamber (where there is more room and the visibility is better), and only after unfolding is complete, then manipulate the lens down into the capsular bag.

With these tactics or their combination, most straight/twisted haptics can be prevented, and the lingering few may be solved without difficulty.