There has been a plethora of advances in the field of keratoplasty over the past 15 years, taking us from an era dominated by full-thickness penetrating keratoplasty to the era of lamellar keratoplasty—a technique that minimizes replacement of the recipient cornea by selectively replacing only diseased corneal stroma. One such technique is warranted in eyes in which the corne- al disease does not involve the endothelium, as it minimizes unnecessary replacement of the healthy endothelial layer: deep anterior lamellar keratoplasty (DALK). The main advantage of the DALK technique is that the eye retains its own endothelium, so that the risk of endothelial rejection—a major cause of graft failure—is eliminated. Today, my lamellar keratoplasty technique of choice is DALK. Because DALK is an extraocular procedure, the eye is much stronger after the procedure than it would be after penetrating keratoplasty. It is also not associated with the sort of intraoperative and long-term complications that are seen with conventional penetrating keratoplasty.

THE PROBLEM AND THE SOLUTION
So why is DALK not enjoying more widespread use around the world? The problem is that DALK is a difficult and long procedure to perform. If it’s not done well, the patient’s visu-al acuity results are worse than they would have been with full-thickness penetrating keratoplasty. One way for DALK to gain more traction as a surgical alternative to penetrating keratoplasty is to try to de-skill the surgical procedure, so that more surgeons can do this safely and effectively. A solution, which has been recently envi- sioned, is to use femtosecond laser technology during the DALK procedure to help creation of the big bubble. I have been using the Femto LDV Z8 (Ziemer) for DALK for the past 6 month in this manner. With the DALK software module on the Ziemer femtosec- ond laser, I use the system’s built-in, intraoperative OCT to guide the depth of the lamellar dissection. This module has a separate corneal patient interface to the one that is used during laser cataract surgery. The module also can be used to make a tunnel incision to easily facilitate creation of the big bubble, allowing me to place the DALK cannula easily through the tunnel (Figure 1). Because of the intraoperative
OCT guidance (Figure 2), these maneuvers are very accurate and more consistent than if performed manually.

ADVANTAGES
Prior to the availability of the DALK software module on the Femto LDV Z8, OCT could only be performed preoperatively to help guide the femtosecond laser depth for the lamellar cut and the sidecut. This limited the usefulness of femtosecond laser technology in the procedure, as the surgeon did not have any real-time data to help guide him or her through the cru- cial steps in DALK. But by having the availability of intraopera- tive OCT, the accuracy of the tunnel incision and the depth of the lamellar dissection is performed in real-time. Following our wet lab studies, I have confidence that the laser will perform these maneuvers with extreme accuracy, and therefore I know
exactly what’s happening to the patient at every point during the procedure. And of course, from one patient to the next, I do not have to worry about varying accuracies in the depth of the dissection and in the creation of the tunnel incision and the big bubble.

Another advantage of the DALK module on the Femto LDV Z8 is that it produces a guided tunnel. What that means is that the tunnel is made with extreme precision, from the lamellar cut to the area in which the tip of the cannula will be. (This is the space in which the surgeon starts injecting air inside the eye to formulate the big bubble—or the separation of the stroma from the Descemet membrane/Dua layer).

The guided tunnel allows me to program the depth of the tunnel, including the starting and the ending depth; the angulation of the tunnel; and the length of the tunnel. Due to the fragility of endothelial cells, one of the issues with per-forming femtosecond DALK is to ensure that the laser pulses
are not too close to the endothelium. During tunnel cre-ation, the ending depth of the tunnel is about 80 to 100 μm away from the corneal endothelium. The Femto LDV Z8 is the only femtosecond laser available today that can be used to produce a guided DALK tunnel. This is because the
laser uses a very low energy laser pulse, making it safe to use so close to the corneal endothelium. With other laser platforms, the energy needed to produce the tunnel at this depth can potentially damage the endothelium.
Another reason that the Ziemer femtosecond laser system can support a DALK software module is because the shots of the laser are fired very closely together, thus producing a smooth tunnel. This enables easy entry of the cannula into and out of the tunnel in order to achieve air separation.

START SLOWLY

The learning curve with the DALK module on the Femto LDV Z8 is relatively straightforward. With that said, it is important for surgeons to keep in mind that they must understandthe entire DALK procedure prior to initiating treatment with this software. Once the procedure is understood and the surgeon is confident enough to begin, the Femto LDV Z8 laser platform is a huge asset to the surgeon in terms of achieving a big bubblea crucial step in the DALK procedure. But there is still the remaining part of the surgery to complete, which involves removing the stroma once the bubble is created and then suturing the graft, which also has to be
performed carefully since there is still a risk of perforation during this part of the procedure. So the Femto LDV Z8 makes a difficult part of the procedure much easier, but the rest of the procedure still must be performed with extreme care. I think that having access to the Femto LDV Z8 DALK software module will significantly cut down on the learning curve of DALK, and it can help most surgeons to achieve a big bubble more frequently than they’re currently achieving. At Singapore National Eye Centre, which is where I work, our conversion rate to full-thickness penetrating keratoplasty from DALK is approximately 0.37%. For comparison, conversion rates in the literature vary from 5% to 30%. Hence, there is a huge variation in the number of cases in which surgeons are able to achieve a successful DALK procedure. I am confident that having the availability of the DALK module on the Femto LDV Z8 would benefit any surgeon and increase his or her success rate with the procedure.
A VERSATILE PLATFORM
I perform a significant number of anterior lamellar keratoplasties at Singapore National Eye Centre, and anterior lamellar keratoplasty accounts for more than 30% of all the corneal transplants that I do every year. That is, however, very high compared to the percentage of anterior lamellar
keratoplasties performed in other centers across the world. In the United States, for example, anterior lamellar keratoplasty accounts for about 2% to 3% of the annual volume of corneal transplant procedures. 1 With this in mind, another nice thing about the Femto LDV Z8 platform is its versatility. The same laser system can be used for cataract surgery as well as corneal surgery—all that is required is switching from one module and patient interface to another. This takes between 5 and 8 minutes to achieve, and it can be done by anyone on the surgical team, not just the surgeon.
CONCLUSION
Applying the functionality of a femtosecond laser to corneal surgery is a big advantage to the field of corneal transplantation, and speaking as a corneal surgeon, I think this has become a reality thanks to all of the many advances being made in laser cataract surgery. Having the availability of one machine that can do multiple procedures, from laser cataract surgery to refractive surgery to corneal surgery, is advantageous to us as surgeons as well as to our patients. Now adding the adjunctive DALK module software onto the Femto LDV Z8 is another step in the evolution of enhanced patient care and de-skilling this procedure. n

1. Eye Bank Association of America. Statistical report. https://restoresight.org/what-we-do/publications/statistical-report/.
   Accessed August 20, 2018.
   JODHBIR S. MEHTA, BS c (HONS), MBBS, P h D, FRCO phth , FRCS(E d ), FAMS
   Head, Corneal and External Eye Disease Department; Senior Consultant,
   Refractive Surgery Department, Singapore National Eye Centre
   Head, Tissue Engineering and Stem Cells Group, Singapore Eye Research
   Institute
   odmehta@gmail.com
   Financial disclosure: Travel support (Ziemer)

BY OZANA MORARU, MD

As anyone who performs cataract and corneal refractive surgeries knows, it is crucial today to have a plethora of procedures and technologies available to patients. This is because there is not one single procedure that fits the needs of every patient. The benefit to offering a variety of corrective procedures, from refractive cataract surgery, to refractive lens exchange, to LASIK, to corneal transplantation, is that you can appeal to a larger patient
base. The drawback, however, can be that your practice requires a lot of different instrumentation in order to carry out the variety of procedures you offer.
One reason our center decided to purchase the Femto LDV Z8 (Ziemer) is because it is a versatile platform capable of performing both corneal and cataract surgeries. Due to the Ziemer femtosecond laser’s relatively small size, we are able to house it in our OR the whole day, during all procedures—even the ones we perform without femtosecond assistance. In this regard, not only do we eliminate the loss of time wheeling equipment in and out of the OR, but it is more comfortable for the patient because we avoid the need to change ORs or even for patients to move between surgical beds in the same OR. Moreover, it allows us to perform both standard cataract surgeries and laser cataract surgeries on the same day, in the same OR, and, in terms of scheduling patients for surgery, it doesn’t matter who has phacoemulsification cataract surgery and who has laser cataract surgery. In other words, we can schedule surgeries in any order, according to the patient’s appointment.

WORKFLOW WITH THE FEMTO LDV Z8
For laser cataract surgery, the patient comes into the OR, we drape him or her, and then we initiate the laser part of surgery. Immediately afterward, we wheel the Femto LDV Z8 a few centimeters away and continue with the manual portions of the cataract procedure. We lower the surgical microscope (which hangs from the ceiling) and start with phacoemulsification; the phaco machine is already close to the surgeon, and the patient is already draped. For corneal transplant surgeries, our workflow is very similar in that all aspects of the procedure can be done in the same OR. First, we prepare the donor cornea with the Femto LDV Z8, and then we perform the transplantation on the recipient cornea with the Z8.

For refractive surgery, most specifically LASIK, we do still need to move the patient to another OR after the Femto LDV Z8 is used to cut the flap, as our excimer laser is housed in another OR. In this scenario, we have one surgeon perform the corneal flap with the Z8 in our main OR and another surgeon immediately afterward perform the LASIK procedure in a secondary OR. This is our typical LASIK work flow because the excimer laser is quite large and cannot fit in our main OR, where we perform cataract and other anterior segment surgeries, and where we have our Z8. In our new clinic, which is about to be finished next year, we will then be
able to update our workflow and house all of our machines in the same OR: one Femto LDV Z8, one excimer laser, and two phaco machines. Thus, all of the cataract and corneal procedures that we perform will be done in the same OR, with a better workflow for all the procedures and for all
patients. Right now, we use the Femto LDV Z8 for the following procedures: cataract surgery, penetrating keratoplasty (mushroom and top-hat designs), deep anterior lamellar keratoplasty (DALK), corneal flaps in LASIK procedures, and tunnel creation for implantation of intrastromal corneal ring segments for keratoconus and corneal ectasia.

MAJOR BENEFITS
Having the possibility to use only one laser machine for all types of procedures has two major benefits: First, the initial investment can be allotted for several patients and surgeries, thus being easier to cover in time and more justifiable, and, second, the laser’s small footprint allows us to be more organized in the OR, in comparison with having several different
lasers for different surgeries. I don’t have clinical experience with every femtosecond laser on the market, but, between the experience I have had
with a couple of other platforms and as far as I have seen during presentations and read in articles, the Femto LDV Z8 seems to be the most versatile femtosecond laser available today worldwide. I previously used the LenSx femtosecond laser (Alcon) for 5 years, but because it can be used for cataract surgery only, such an expensive machine was not feasible in our practice, and we could not justify the investment.
Moreover, it is a big machine and it requires permanent air conditioning, a continuous low temperature, and a certain humidity, all of which made our surgical costs even higher.

Figure 1. The Femto LDV Z8 used during nucleus fragmentation (left and right).

On the other hand, the Z8 has a smaller footprint, it is easy to handle, it is mobile, and there are no environmental necessities.
Above all, it allows better cutting precision and safety during surgery. Therefore, it can be used as often and for as many procedures as possible. We have found that it is easy to dock; there are few patient complaints; it produces perfect corneal incisions and capsulotomies; and we have experienced no vacuum loss, no miosis, nor conjunctival hemorrhages. In terms of corneal surgery, we noticed precision in cutting the clear corneal tissue, both in LASIK cases and in corneal transplant procedures.

CASES IN POINT
White cataracts. Nuclear fragmentation is very well performed with the Femto LDV Z8, even in hard nuclei and white cataracts (although the fragmentation pattern is not always visible from the beginning). For this reason, we almost exclusively perform laser cataract surgery in white cataracts, as it brings a lot of advantages. First, most of these cataracts are
intumescent, with a flat anterior chamber and liquefied cortex. With the subsequently narrow angle, an accidental puncture of the iris or anterior
capsule is more likely with conventional phacoemulsification cataract surgery requiring limbal or clear corneal incisions; this complication is avoided using the femtosecond laser, where OCT technology warns of this possibility and helps the surgeon set proper incision placement.

Figure 2. Mushroom keratoplasty with the Femto LDV Z8
(top, center, and bottom).

Second, the prominent dome of the anterior capsule and the liquefied pressurized cortex in the white intumescent cataract often predispose capsular run-out

(ie, Argentinian flag syndrome) in conventional phacoemulsification with manual capsulotomy. On the contrary, by performing the capsulotomy with the Femto LDV Z8, we can avoid the high possibility of an Argentinian flag syndrome, and we also can safely create the capsulotomy in the desired size and position.
Third, the Femto LDV Z8 brilliantly cuts the nucleus of a white cataract. This can easily be seen when attempting to split the nucleus into pieces: The nucleus pieces exhibit a straight and vertical cut and are very easy to separate during phacoemulsification, which is a sign of an efficient laser precut. Posterior polar cataracts (PPC). When fragmentation is already done by the laser (Figure 1), it avoids the necessity to chop or sculpt the nucleus manually by rotating and splitting it. The surgeon is no longer required to separate the fragments with lateral movements; thus, we avoid the dangerous rotational and lateral forces needed for manual nucleus fragmentation and separation—forces that would put the weakened central zone of the posterior capsule in PPC eyes at risk for major complications.
In these cases, I recommend use of a femtosecond laser pattern with several radial cuts in the nucleus (16, for example).
This results in several smaller fragments that can easily be emulsified and aspirated, without any dangerous force exerted on the posterior capsule. Moreover, because the polar posterior opacities can be seen on OCT, the surgeon can precisely set the depth of the radial nucleus cuts, very close to the posterior capsule, making fragmentation even more complete and efficient.

Lamellar keratoplasty. I consider femtosecond technology very useful in corneal transplant surgeries. In DALK, the Femto LDV Z8 brings more precision in performing the circular cut at the correct depth and in tunnel creation in the big-bubble technique. However, it is equally useful in penetrating keratoplasties. For example, in very advanced keratoconus,
central leucomas, and scars, or in an eye with hydrops, the Femto LDV Z8 allows one to make a large graft to better cover the ectasia and to reduce postoperative astigmatism.

How can we obtain all these requirements? By performing a mushroom keratoplasty with the Femto LDV Z8, which can be safely tailored to the patient’s ectatic cornea (Figure 2) and by the use of integrated intraoperative OCT.

CONCLUSION
The Femto LDV Z8 is a versatile, compact, and precise platform capable of performing both cataract and corneal refractive surgeries. We have found it to be a welcomed addition in our OR as well as useful in not just routine cases but also complex cases as well.
OZANA MORARU, MD
Medical Director, Oculus Private Eye Clinic, Bucharest, Romania
ozana@eye.ro
Financial disclosure: None

Early signs of corneal asymmetries are often visible on the posterior surface first – and that’s why the reliable measurement of both anterior and posterior surfaces is vitally impor tant. GALILEI, a diagnostic device from Ziemer, is able to make all the measurements required for cataract and refractive surgery planning in a single session, making it a truly complete solution for ophthalmic surgeons.

Placido topography, Dual-Scheimpflug tomography, and optical biometry, with all measurements aligned to first Purkinje reflex, are combined within the GALILEI device to assist surgeons in reliably measuring the anterior and posterior surfaces, as well as the eye’s axial length. The system’s two Scheimpflug cameras provide precise pachymetry and elevation data, which aid in the early detection of asymmetry and bulging.

Figure 1. The Ziemer GALILEI device.

Renowned cornea and refractive surgeon Shady Awwad, Associate Professor of Clinical Ophthalmology and Director of the Refractive Surgery Center at the American University of Beirut, uses GALILEI’s Dual-Scheimpflug to screen candidates for laser vision correction. For the last few months he has been using GALILEI’s latest report, to be added shortly: the Corneal Thickness Progression Report. The report, which consists of three x/y graphs, four maps, and a set of indices, compares the patient’s measured data with data from the normal population, and shows the change in corneal thickness towards the periphery relative to the thinnest point. Awwad says, “I believe the Corneal Thickness Progression Report is one of the most sensitive tools to help detect early ectasia. I start the analysis by looking at the captured image, to make sure the measurement is unobstructed and centered, and to assess the position of the measurement center vis-à-vis the center of the cornea.” Awwad then evaluates the “Quadmap” (the anterior and posterior instantaneous curvature, posterior Best Fit Sphere, and pachymetry maps, see Figure 2) before checking the Corneal Thickness Progression Report. Awwad says the report is invaluable when planning his surgeries: “The Corneal Thickness Progression Report is key in identifying very early ectatic corneas (keratoconus suspects), and I have found it to be very sensitive and capable of producing specific data. It often shows values positive for early ectasia when other traditional parameters show normal to borderline levels. I believe it provides an extra safety net in making the decision whether or not to proceed with laser vision correction.” (see Figure 3) In addition to the x/y graphs, the Report includes a Corneal Thickness Progression map, which visualizes the data in an easy-to-read map. It is unique, as it provides surgeons with the precise location of suspicious regions within the cornea. Awwad says, “The Corneal Thickness Progression map displays the rate of change in corneal pachymetry with respect to the thinnest point at any given point in the cornea. Whereas the x/y graphs average corneal thickness change at a given distance from the thinnest point and over all meridians. The problem with the latter approach is that early abnormal pachymetric changes, typically focal, will be diluted by the system, averaging them with other areas in the cornea. Instead, the Corneal Thickness Progression map can help the clinician depict an early focal pachymetric change, typically infero-temporal or inferior, that is faster than in the rest of the corneal areas, and potentially faster than the expected normal range. This has been shown to be one of the earliest manifestations of ectasia.”

In summary, the additional information provided by the GALILEI helps clinicians with diagnosis and decision making – thus offering solid support in refractive surgery planning. Shady Awwad draws a strong conclusion: “The Corneal Thickness Progression Report is a boon for ophthalmologists involved in laser vision correction. Used in combination with other parameters, it allows us to make confident surgical decisions.”

Figure 2. “Quadmap” tomography of the right eye of a patient with left eye
keratoconus. The patient’s right eye shows no obvious signs of the disease.

Figure 3. Corneal Thickness Progression Report of the same patient’s
right eye. The rate of pachymetry change is highest at the
inferotemporal quadrant, as opposed to the other sectors, specifically
the superonasal quadrant, signaling early ectatic disease in the
seemingly normal right eye.

The GALILEI G4 is CE marked and FDA cleared. The GALILEI G6 is CE marked and pending FDA clearance. For some countries, availability may be restricted due to regulatory requirements. Please contact Ziemer for details.