Using the techniques for visualizing stromal dissection depth as described in Chapter 2, deep anterior lamellar keratoplasty procedures were performed in a series of 68 patients, after an Institutional Review Board-approved informed consent was obtained from each patient (Figure 4.1).

Figure 4.1: Diagrammatic representation of the deep, anterior lamellar keratoplasty technique. (a) After dissection of a deep stromal pocket through a scleral incision, (b and c) visco-elastic is injected into the pocket, and an anterior corneal lamella is trephinated from the recipient cornea. (d) After stripping Descemets membrane, a full-thickness donor corneal button is sutured into the recipient stromal bed. Compare to Figures 2a-c and 3a-f. (Source: Br J Ophthalmol 1999;83:327-333)

In recipient eyes, a self-sealing side port was made at the 9 o clock limbus, to aspirate the aqueous using a blunt canula, and to completely fill the anterior chamber with air. At the 12 o clock limbus, the conjunctiva was opened and a superficial scleral incision was made, 5.0 mm in length, 1 mm outside the limbus. With a custom made dissection blade (DORC, Zuidland, The Netherlands), a lamellar dissection was made to just within the superior cornea.

At this point, the tip of the blade was slightly tilted downward to visualize the interface between the air bubble in the anterior chamber and the corneal endothelium; underneath the corneal dimple, the air-to-endothelium interface was seen as a specular light-reflex localized at the tip of the blade (Figure 4.2a). Between the blade tip and the light-reflex, a non-reflective, dark band was seen, representing the non-incised corneal tissue between the blade and the air-to-endothelium interface. Because the dark band became thinner with advancement of the blade into the deeper stromal layers, the corneal depth of the blade could be judged from the thickness of the dark band (Figure 4.2b).

When the tip of the blade appeared to touch the air-to-endothelium light-reflex (Figure 4.2c), i.e. the posterior corneal surface, the blade was positioned parallel to the posterior surface, for dissection of a stromal pocket across the cornea, just anterior to the posterior corneal surface (Figures 4.1a and 4.3a).

Figure 4.2: Demonstration of the surgical technique in a human eye bank eye. (a) The anterior chamber has been filled with air. In between the blade tip and the air-to-endothelial interface light-reflex, a dark band is visible. (b) Because the dark band reflects unincised posterior corneal tissue, the dark band decreases in width when the blade is advanced into the deeper stromal layers. (c) When the blade appears to touch the air-to-endothelium interface, a stromal dissection level just anterior to the posterior corneal surface is reached. (Source: Br J Ophthalmol 1999;83:327-333)

After a deep stromal pocket was created up to the limbus over 360°, the air was removed from the anterior chamber, and a visco-elastic (Hydroxypropylmethylcellulose, Ocucoat, Storz, Clearwater, FL, USA) was injected through the scleral incision into the stromal pocket (Figures 4.1b and 4.3b). Thus, the posterior corneal lamella was separated from the overlying anterior stroma, to avoid perforation of the posterior corneal surface during trephination. Then, a Hessburg-Barron suction trephine was centered over the anterior corneal surface (Figure 4.3c). The blade was turned downward until the stromal pocket was just entered, i.e. until visco-elastic was seen to escape from the pocket through the trephine incision. Remaining, unincised stromal attachments of the anterior lamella were cut with curved microscissors, the anterior corneal lamella was removed, and the recipient bed was thoroughly irrigated to remove all visco-elastic and debris (Figures 4.1c and 4.3d).

Figure 4.3: Demonstration of the surgical technique in a human eye bank eye. (a) The pocket is dissected first across the vertical meridian, and then extended sideways up to the limbus over 360 degrees, with the same spatula. Note that the anterior chamber is completely filled with air, and that the dissection depth can be monitored by the width of the dark band (arrowheads) in between the spatula and the air-to-endothelium light-reflex. Note also the wrinkling of the posterior corneal tissue (arrow). (b) After most air has been removed from the anterior chamber, the stromal pocket is filled with visco-elastic. Note the step-ladder configuration of the relaxed posterior corneal tissue (arrow) that is pushed downward. (c) After trephination with a Hessburg-Barron trephine (d) an anterior corneal lamella is excised. Note the smooth recipient bed (asterisk) with some residual posterior stroma overlying the pupillary border (arrowheads). (e) After stripping Descemets membrane, a full-thickness donor button (arrow) is placed onto the recipient bed, and the donor and recipient corneal surfaces are marked with an eight incision radial keratotomy marker. (f) The donor button sutured in place with two running sutures. (Source: Br J Ophthalmol 1999;83:327-333)

After removal of Descemets membrane (see Chapter 6), the donor button was transferred to the recipient stromal bed, and the donor and recipient corneal surfaces were marked with an eight incision radial keratotomy marker (Figure 4.3e). The button was sutured into the recipient bed with two running, 10-0 monofilament nylon sutures (Alcon, Gorinchem, The Netherlands) (Figure 4.3f). The tension of the sutures was adjusted until the anterior, donor corneal surface reflected a spherical image of a Placido-disc held about 3 cm above the recipient eye.

Figure 4.4: Light microscopy of a deep lamellar dissection through a scleral incision in a human eye bank eye. A deep stromal dissection level is seen (98% corneal depth). Few stromal lamellae are visible between the stromal dissection and Descemets membrane (Hematoxylin-eosin, original magnification x35 and x450).

Figure 4.5: Slit-lamp photograph six months after DALK. A clear lamellar corneal transplant is visible, with a deep stromal donor-to-recipient interface.