Big bubble technique offers variation of anterior lamellar keratoplasty

Surgeons explain how a blunt cannula is used to inject air and create the big bubble.

Issue: November 1, 2007

Introduction

Anterior lamellar keratoplasty is a useful surgical technique that retains the patient’s healthy endothelium and hence eliminates corneal endothelial graft rejection. The surgeon has to be skilled and experienced in lamellar corneal surgery, especially when performing a deep or total ALK, to prevent or minimize the risk of Descemet’s membrane tear. There are several surgical techniques to perform ALK. My guests in this column, Pierre Fournié, MD, and Jean-Louis Arné, MD, of Purpan Hospital in France, describe how to use air to perform ALK. They use a blunt cannula instead of a sharp needle and use a layered approach in performing ALK.

Thomas John, MD
OSN Corneal Dissection Editor

The technique can be performed under general or peribulbar anesthesia.

A host corneal trephination is performed with a Hanna suction trephine (Moria) to a corneal depth of 50% to 75% of the preoperative pachymetric measurement of the central corneal thickness. A 30.5-gauge disposable needle attached to a 5 mL sterile airtight syringe (Figure 1a) is inserted from the limiting circular cut made by the trephine. Air is injected with the needle bevel oriented downward (Figures 1a and 1b). The purpose of the first air injection, compared with the original technique, is to obtain a corneal emphysema (Figures 1a and 1b) and not a big bubble. A big bubble, however, sometimes forms at this stage, as is described in the previous technique, depending on the depth of the needle tip, which is difficult to assess under the operating microscope. The stromal emphysema that is formed by separating the collagen lamellae facilitates the anterior lamellar keratectomy with a rounded blade (Beaver blade, BD sclerotome multi-sided blade, #375700) (Figures 1c and 1d). The thickness of the anterior corneal lamella should not exceed two-thirds of the corneal thickness at this stage of the operation.

Air is injected through a 30.5-gauge disposable needle from the limiting ring of the partial-thickness trephination (1a). A white corneal emphysema, separating the collagen lamellae, spreads from the tip of the needle (1a) to the limiting ring (1b). The emphysema is contained to the limiting ring (1b), provided that the needle is not inserted too deeply. Disruption of collagen lamellae by air facilitates dissection (1c) and excision (1d) of an anterior corneal lamella that should not exceed two-thirds of the corneal thickness.

Images: Fournié P

A nonpenetrating stromal corneal “nick” is then performed, slightly inside the limiting ring, with the sharp tip of a 15° disposable knife (Sharpoint 15° stab knife straight, #721501, Angiotech) (Figure 2a). We recommend making the corneal stromal nick slightly oblique and not perpendicular to the corneal surface in order to extend the intrastromal trajectory and facilitate the insertion of a blunt cannula (Rycroft-type, BD Visitec anterior chamber cannula, 40 × 22 mm, 27-gauge, #581280) through this nick (Figure 2b). Intrastromal swelling and diffuse disruption of the corneal stromal tissue along different planes after the first air injection facilitate the progression of the blunt cannula by rotating the air-filled syringe, onto which the cannula is mounted (Figure 2b). Air is injected with the tip of the cannula oriented downward, in occlusion against the corneal stroma (Figure 2c). Air injection will either result in a big bubble formation (Figure 2c) or in a corneal, stromal emphysema in a deeper plane. In this case, another manual lamellar keratectomy can be performed and the later steps are repeated until a big bubble forms. The appearance of the big bubble can be either “explosive,” as described by Anwar and Teichmann, with a peripheral whitish, semi-opaque disc, or more progressive. The centrifugal progression of the bubble can often be controlled by the surgeon depending on the rate of air injection (Figures 2c and 2d).



A nonpenetrating stromal corneal nick is placed (2a) inside the limiting ring with the sharp tip of a knife oriented slightly oblique and not perpendicular to the surface. A blunt cannula is inserted through the nick by firmly grabbing the inner edge of the nick with forceps (2b). With the tip of the blunt cannula sufficiently inserted and oriented downward, air injection often results in the formation of a big bubble, progressing centrifugally (arrows) from the tip of the cannula (2c) to the limiting ring (2d). We recommend against interrupting air injection until the bubble is complete (2d).

Obtaining the big bubble

Once an air bubble is obtained, air is exchanged for viscoelastic, namely Healon GV (sodium hyaluronate 1.4%, Advanced Medical Optics). Some pressure is exerted on the blunt cannula to penetrate the remaining stroma. A slight cut can also be made to the remaining stroma to “open the bubble.” In either case, the air bubble collapses. The bubble is recreated by injection of viscoelastic. It is important to inject the viscoelastic slowly and in small quantities in order to not see any unusual distension of the bubble or increased IOP. If necessary, a sideport incision can be made to control the IOP. However, we recommend not making this incision before a big bubble is obtained, to maintain the natural counter-pressure of the eye when inserting the cannula and injecting air. Viscoelastic progression can easily be followed within the bubble. Viscoelastic is allowed to reach the diameter of the trephination, while detaching residual adherences between Descemet’s membrane and the corneal stroma. It also facilitates pre-Descemetic manipulations. The stroma is incised along the body of the cannula (Figure 3a on page 120) and the remaining stroma is excised with curved microscissors along the limiting ring cut made by the trephination (Figures 3b and 3c on page 120). After washing out the viscoelastic (Figure 3d on page 120), the corneal graft, stripped of Descemet’s membrane and endothelium (Figure 4a on page 120), is sutured in the uniform recipient surface (Figures 4b and 4c).



After air has been replaced by viscoelastic, the body of the cannula is inserted within the bubble and guides the cut of the overlying stroma (3a). The remaining stroma is then cut along the limiting ring with curved microscissors (3b) and excised (3c). A smooth and uniform surface is obtained after washing out the viscoelastic (3d).

Pearls

The initial trephination with the Hanna suction trephine should not be greater than 75% (preferably less) to prevent inadvertent full-thickness trephination of the patient’s cornea.

The use of a blunt cannula reduces the risk of accidental intraoperative corneal perforation while inducing a big bubble.

It is important to maintain a safe distance from the posterior corneal surface to limit the risk of perforating or tearing Descemet’s membrane.


	The corneal donor button is stripped of Descemet’s membrane and endothelium with forceps (4a) and sutured in the recipient’s corneal bed (4b and 4c).

Treatment

Antibiotic drop such as Zymar (gatifloxacin, Allergan) or Vigamox (moxifloxacin, Alcon) may be used 3 days before surgery.

Celluvisc lubricant eye drops (carboxymethylcellulose sodium 1%, Allergan) and a topical combination of 0.1% dexamethasone and neomycin four times a day each are prescribed after surgery. Alternatively, Pred Forte 1% (prednisolone acetate 1%, Allergan) and gatifloxacin or moxifloxacin one drop four times a day may be used during the preoperative and postoperative period and then discontinued. For graft protection, the patient is asked to wear glasses or an eye shield during the day and a shield at night. Postoperative suture adjustment is performed at the slit lamp approximately 3 to 6 months after surgery.

For more information:
Thomas, John, MD, is a clinical associate professor at Loyola University in Chicago and in private practice in Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; e-mail: tjcornea@gmail.com. Dr. John has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
Pierre Fournié, MD, and Jean-Louis Arné, MD, can be reached at Department of Ophthalmology, Purpan Hospital, Toulouse 31000, France.

References:

Anwar M, Teichmann KD. Big-bubble technique to bare Descemet’s membrane in anterior lamellar keratoplasty. J Cataract Refract Surg. 2002;28(3):398-403.
Anwar M, Teichmann KD. Deep lamellar keratoplasty: surgical techniques for anterior lamellar keratoplasty with and without baring of the Descemet’s membrane. Cornea. 2002;21(4):374-383.
Fournié P, Malecaze F, Coullet J, Arné JL. Variant of the big bubble technique in deep anterior lamellar keratoplasty. J Cataract Refract Surg. 2007;33(3):371-375.
John T. Selective tissue corneal transplantation: a great step forward in global visual restoration. Expert Rev Ophthalmol. 1:5-7;2006.
John T, ed. Step by Step Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006.
John T, ed. Surgical Techniques in Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006.