Femtosecond DALK with added technique successful in pediatric patients

Technology may offer the possibility of a safer, more reproducible technique, rendering DALK a feasible option for children.

Issue: September 2011

Luca Buzzonetti

A femtosecond laser-assisted variation of the classic big-bubble technique in deep anterior lamellar keratoplasty showed a high degree of reproducibility and easier management in pediatric patients, according to a surgeon.

There are several indications for primary keratoplasty in pediatric patients, Luca Buzzonetti, MD, said at the winter meeting of the European Society of Cataract and Refractive Surgeons in Istanbul. Congenital opacities account for 62% of cases, acquired nontraumatic opacities for 21% and traumatic opacities for 17%. The most commonly performed technique is penetrating keratoplasty, but the main problem with this technique, as reported in the literature, is graft rejection.

“Graft survival in children after PK is 50% at 1 year,” Dr. Buzzonetti said.

Options

Theoretically, lamellar keratoplasty offers an alternative, but technical difficulties are even greater in very young eyes. As a result, there are few published studies on deep anterior lamellar keratoplasty (DALK) for pediatric patients.

The eye is immobilized with four sutures in the conjunctiva.

“As a pediatric ophthalmologist and IntraLase user, I wondered if the femtosecond laser might not be the answer that makes DALK safer, more reproducible and therefore more feasible to use in children,” Dr. Buzzonetti said. “Of course, this answer could not be straightforward, because femtosecond lasers are conceived for adults. The suction ring is too large, and we don’t know how suction in general might affect small eyes. Another thing we didn’t know was if the gas anesthesia could affect the efficacy of the femtosecond laser. I thought that with some adjustments of the machine and the technique, it was worth trying.”

Under general anesthesia, using the 60-kHz IntraLase femtosecond laser (Abbott Medical Optics) loaded with the Intra-Lase-enabled keratoplasty computer program for zigzag incisions, DALK was performed in nine eyes of pediatric patients with keratoconus or corneal opacities.

Technique

In the smallest eyes, no suction ring was used because its size was too big. The laser cone was applied directly onto the eye surface. To avoid unwanted eye movements, silk sutures were fixed through the skin (Figure 1).

The IntraLase femtosecond laser creates the intrastromal channel 50 µm above the thinnest point of the cornea.

A variation of the classic big-bubble technique was applied. The “IntraBubble” technique entails the preparation by femtosecond laser of a pre-Descemet dissection plane, 100 µm from the endothelium, and the creation of a small channel in the posterior stroma (Figure 2), 50 µm from the endothelium, into which a smooth, flat 27-gauge cannula for air injection can be introduced. A zigzag lamella is then created, again using the femtosecond laser, reaching in depth the 100-µm dissection plane. Before inserting the air cannula, the channel is lengthened using a pointed dissector.

Air is inflated to create a big bubble (Figure 3), after which the procedure continues according to classic big-bubble technique.

“I perform the bubble test to confirm the presence of the big bubble. Then I perforate the bubble and refill the space with viscoelastic to push down the Descemet’s and protect it while I complete the stromal removal by scissors. The donor lamella, previously prepared by the IntraLase using the same technique, is positioned and secured with single sutures,” Dr. Buzzonetti said.

Results

Using this method, the big bubble was achieved in 100% of cases. Six months after surgery, with sutures in place, best corrected visual acuity was 20/25, spherical equivalent was –2.5 D and topographic astigmatism was 4.5 D.

The big bubble is achieved.

Image: Buzzonetti L

At the Bambino Gesù Hospital in Rome, where Dr. Buzzonetti practices, 24 pediatric keratoplasties were performed in the past year. Twenty of them were DALK, nine of which were assisted by femtosecond laser. The mean age was 8 years (range: 1 year to 15 years).

“Of course, more patients and a longer follow-up are needed, but we have been able to prove that the femtosecond laser can be successfully used in selected pediatric cases, using specific precautions and a specific technique,” Dr. Buzzonetti said.

The femtosecond laser offers the opportunity to standardize the procedure using a predefined corneal depth. Surgical time is shorter and safety is greater, with a decreased risk of inadvertent perforation. The technique can be available to more surgeons, with a shorter learning curve compared to standard DALK.

“There are still a few disadvantages and problems, such as the cost of the laser and the need to adapt the machine and software to small eyes,” Dr. Buzzonetti said. – by Michela Cimberle

Luca Buzzonetti, MD, can be reached at Bambino Gesù Children’s Hospital, Piazza Sant’Onofrio 4, 00165 Rome, Italy; email: luca.buzzonetti@opbg.net.
Disclosure: Dr. Buzzonetti has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.

Corneal opacities in children are commonly treated by penetrating keratoplasty. Because of the high rate of graft rejection, deep anterior lamellar keratoplasty assisted by femtosecond laser appears to be an interesting alternative. As the author said, technical characteristics must be adjusted to children.

The IntraBubble technique described by the author offers a safer alternative for small eyes because it creates the bubble through a pre-Descemet, small-channel laser dissection. This procedure may well be worth the additional cost, because it is safer than big-bubble and needs a shorter learning curve.

Further studies with longer evaluation of the young patient grafts are needed and additional selected pediatric cases must be performed, hopefully using new dedicated laser software and hardware parts adapted to the specific needs of small eyes. In this way, we could obtain a standard DALK procedure, reproducible for pediatric corneal opacities.

— Dominique Brémond-Gignac, MD, PhD
OSN Europe Edition Editorial Board Member
Disclosure: Dr. Brémond-Gignac has no relevant financial interests.