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Refractive Surgery | Sep 2010

The IntraBubble: A Variant of the Big Bubble

A femtosecond-assisted deep anterior lamellar keratoplasty technique.

Deep anterior lamellar keratoplasty (DALK) is a proposed alternative to penetrating keratoplasty (PKP) for the treatment of various corneal diseases not affecting the endothelium. 1,2 This surgical procedure selectively removes pathologic corneal stromal tissue down to Descemet's membrane, preserving the patient's own endothelium and reducing the risk of immunologic reactions and graft failure. However, the technical difficulties, protracted operating times, and risk for intraoperative corneal perforation historically limit the success of DALK.

After the introduction of the femtosecond solid-state laser to ophthalmology,3 surgeons began successfully incorporating this technology into corneal surgical procedures. 4-6 We propose a variant of the big-bubble technique for DALK, the IntraBubble, using the IntraLase femtosecond laser (Abbott Medical Optics Inc., Santa Ana, California). This technique may help to partially standardize the big-bubble technique and, in cases with intraoperative complications, simplify conversion to PKP, resulting in better fit of the donor cornea and positive refractive outcomes.

TECHNIQUE
The procedure begins with marking the center of the recipient cornea. The femtosecond laser then creates an intrastromal channel 50 μm above the thinnest corneal point, as measured by the Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), with a 30° angle and 25° arc length. Then, a 9.5-mm lamellar cut is performed 100 µm above the thinnest corneal point. At the same depth, the laser immediately creates a zigzag lamella. The recipient lamella is then removed, and a Fogla pointed dissector (Bausch + Lomb, Rochester, New York) is used to lengthen the stromal channel. A Fogla 27-gauge air injection cannula (Bausch + Lomb; Figure 1), attached to a 5-mL syringe filled with air, is inserted and slightly advanced into the channel. The air is forcefully injected into the stroma, forming a big bubble (Figure 2).

A peripheral paracentesis is performed, allowing some aqueous to escape so that the intraocular pressure decreases. A small air bubble is injected into the anterior chamber to verify that Descemet's membrane has been bared. A 15° disposable knife is then used to perforate the bubble, and an ophthalmic viscosurgical device (OVD) is injected to refill the space and protect Descemet's membrane. The residual stroma is excised down to Descemet's membrane with corneal scissors. Lastly, the donor lamella, previously prepared by IntraLase, is fitted into place and sutured with 16 interrupted 10-0 monofilament nylon sutures.

RESULTS
Our IntraBubble technique has been performed in 20 patients with keratoconus (mean follow-up, 1 month). All patients were consecutively operated on by one surgeon (LB) using the IntraLase Enabled Keratoplasty (IEK) computer program for zigzag incisions.

All procedures were completed as DALK. The big bubble was achieved in 17 eyes (85%). In three eyes, intraoperative microperforations required transition to hand dissection.

Results with this technique are promising. In our opinion, the access created by the femtosecond laser allows the maintenance of a predefined corneal depth very close to the endothelium and provides a good chance for success in achieving the bubble (85%) compared with the manual technique (approximately 60–65%).7-9 No case in this series required conversion to PKP.

CONCLUSION
Further long-term study of this approach is warranted. Our preliminary results indicate that the IntraBubble technique may assist in standardization of the big-bubble technique for DALK, reducing the learning curve and the risk of intraoperative complications. Our new technique should greatly decrease intraoperative perforations, which are the largest risk with manual big-bubble techniques. The IntraBubble technique should produce good refractive outcomes.

Luca Buzzonetti, MD, practices in the Ophthalmology Department, Bambino Gesù Children's Hospital, Rome. Dr. Buzzonetti states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +39 3386899038; fax: +39 0668593281; e-mail: lucabuzzonetti@yahoo.it.

Antonio Laborante, MD, practices in the Ophthalmology Department, Casa Sollievo della Sofferenza Hospital, San Giovanni Rotondo (Foggia), Italy. Dr. Laborante states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: antoniolaborante@virgilio.it.

Gianni Petrocelli, MD, practices in the Ophthalmology Department, Bambino Gesù, Children's Hospital, Rome. Dr. Petrocelli states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: gpetrocelli@tin.it

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