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ALK useful for corneal perforations

In this new OSN column, a surgeon explains the preparation and intraoperative techniques of automated anterior lamellar keratoplasty.

Issue: July 1, 2007

ByThomas TJ John, MD

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Anterior lamellar keratoplasty is a useful surgical procedure in the management of corneal perforation (Figures 1-13). It may be preferred over therapeutic penetrating keratoplasty, thus avoiding opening the globe in an inflamed eye and risking the potential loss of intraocular contents in a possible expulsive hemorrhage during surgery or introducing infective organisms into the interior of the globe and converting a corneal infection into potential endophthalmitis. Surgeons should avoid doing anterior lamellar keratoplasty, or ALK, in the presence of an active corneal infection. ALK may be combined with human amniotic membrane transplantation.

Anesthesia

General anesthesia is preferred for ALK, especially if there is a large corneal perforation of more than 2 mm in diameter.

In a small corneal perforation of less than 2 mm in diameter, either general anesthesia or topical anesthesia with monitored anesthesia care can be used. Xylocaine 2% jelly (lidocaine HCL, AstraZeneca) is applied to the ocular surface (Figure 4).

Surgeons should avoid putting any undue pressure on the globe during surgery.

Donor corneal preparation

The donor corneal button is obtained from a local eye bank. It is essential to request that the donor corneal rim has a uniform scleral width of 4 mm, or at least more than 3.6 mm, to prevent potential donor button slippage within the artificial anterior chamber. If available, obtain a backup donor cornea. The donor corneal button may be prepared manually or automated, namely microkeratome-assisted preparation. I prefer to use an automated technique, which will be described in this article.

For the automated dissection of the donor corneal disc, a Moria anterior lamellar therapeutic keratoplasty unit and a Moria disposable 130-µm CB-head are required (Figure 3). The microkeratome pass is performed slowly, resulting in a donor disc of about 160 µm to 170 µm thickness. Before trephination, it is essential to increase the intra-chamber pressure above 65 mm Hg, so that the cornea is firm to palpation, in the artificial anterior chamber. Palpation is adequate, and a tonometer is not essential for this step of the surgery. It is important to tighten the rings in the artificial anterior chamber for proper fixation of the donor corneal button within the artificial anterior chamber. Remove the donor corneal epithelium in combined ALK-amniotic membrane transplantation procedures. Moisten the microkeratome and the donor cornea in the artificial anterior chamber with sterile balanced salt solution. Alternatively, ALK can be performed using a manual dissection technique.

The prepared donor corneal disc may be placed in the Optisol GS solution (Bausch & Lomb) provided by the eye bank and kept in a secure location on the side table until ready to use on the host cornea.

Host corneal surgery

In cases with a corneal perforation (Figure 1), fluorescein staining of the cornea will usually demonstrate a positive Seidel test (Figure 2). It is important to remove the host corneal epithelium surrounding the ulceration to facilitate donor corneal disc adherence. A straight crescent blade from Alcon is used (Figures 5a and 5b). The prepared donor lamellar corneal disc (Figure 6) is attached to the host globe at the 6 o’clock position using a single 10-0 nylon suture (Figure 7). The donor lamellar disc is then partially flipped to expose the stromal side of the disc. For tissue adhesive (Tisseel VH fibrin sealant, Baxter), component 1 is applied to the host corneal surface (Figure 8), and component 2 is applied to the stromal surface of the donor lamellar disc (Figure 9). The lamellar donor corneal disc is then attached to the host cornea by flipping the disc back in place to cover the host corneal ulceration/perforation site and the area of descemetocele, using the anchoring suture to facilitate this motion of donor cap attachment. Gentle, even pressure is then applied to the donor corneal surface to enhance approximation and donor-host corneal adhesion as the two components, fibrin and thrombin, interact (Figure 10).

Amniotic membrane use in these cases is optional and of surgeon preference. I use amniotic membrane, as a single layer on the ocular surface, primarily to decrease ocular inflammation and help facilitate the healing process. The amniotic membrane is tacked at three points using interrupted 10-0 Vicryl sutures. The amniotic membrane is then flipped on itself to expose the stromal connective tissue surface of the amniotic membrane (Figure 11). For tissue adhesive, component 1 is applied to the cornea and the surrounding conjunctiva (Figure 12), and component 2 is applied to the exposed stromal surface of the amniotic membrane (Figure 13). It is of no consequence which component is used first. Excess amniotic membrane is trimmed using Vannas or Westcott scissors (Figure 13, page 55). Subconjunctival antibiotic and corticosteroid injections are administered. Antibiotic-steroid combination ophthalmic ointment is applied to the ocular surface and the eye is patched, and then, a Fox eye shield is taped in place.

Treatment

Preoperatively, place an eye shield for ocular protection at all times. Continue preop antibiotic drop, and do not use topical corticosteroid drops.

Intraoperatively, use the normal surgical prep that is used for any intraocular surgery.

Postoperatively, topical steroid and latest-generation fluoroquinolone ophthalmic drops are applied four times a day. For globe protection, the patient is asked to wear glasses or an eye shield during the day and a shield at night. There should be the usual limitations on postoperative activity.

At a later date, when the eye has fully healed and is no longer inflamed, additional surgery may be planned for visual restoration.

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., and Hammond, Ind. He can be reached at 708-429-2223; fax: 708-429-2226; e-mail: tjcornea@gmail.com. Dr. John has no proprietary interest in any aspect of this article.

References:

• John T. Surgical Techniques in Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006:1-687.
• John T. Step by Step Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006:1-297.
• John T. Selective tissue corneal transplantation: a great step forward in global visual restoration. Expert Rev Ophthalmol. 2006:1(1);5-7.
• John T. Human amniotic membrane transplantation: past, present, and future. Ophthalmol Clin North Am. 2003;16(1):43-65.
• Selvadurai D, John T, et al. The ideal size of human donor corneoscleral explants from eye banks used in artificial anterior chambers. Presented at: Annual Meeting of the Association for Research in Vision and Ophthalmology; 2005; Fort Lauderdale, Fla.