**4. Surgical techniques**

The superiorities of DALK over penetrating keratoplasty cannot be overemphasized. However, for obtaining best results, a corneal surgeon must be familiar with different surgical maneuvers used for performing DALK. In this overview of some techniques for performing DALK, some surgical "pearls" will enrich our repertoire of skills.

## **4.1 Using air to perform DALK**

In 1984, Arenas introduced the concept of injecting air into the corneal stroma for performing DALK and the technique was named air-deep lamellar keratoplasty (AD–LKP) (Arenas, 1985). He injected air into superficial corneal stromal tissues at the peripheral cornea. Then a partial-thickness trephination cut of about 400 µm was performed in the resultant emphysematous, white corneal tissue. The superficial corneal layers were removed using sharp blades and deep stromal layers were removed using blunt spatulas until reaching the pre-Descemet level. The movement of the spatulas was centripetally starting at the wound margins and ending at the center or thinnest part of the cornea. He described the pre-Descemet layer as a black and shiny surface devoid of air. The DM was not exposed by this technique; however, after long-term follow-up, the visual results were better than those for penetrating keratoplasty.

#### **4.2 Using shearing and traction force instead of cutting to perform DALK**

Malbran introduced the peeling-off technique (Malbran, 1966). His concept of a peeling rather than a cutting action for removing the recipient's corneal stromal tissues provided a smoother surface that served as the bed for transplantation. In this technique, the stromal tissues are pooled in a direction that is perpendicular to the corneal surface and a semisharp instrument leads the direction of shearing of tissue through the corneal stromal layers. He also modified his technique by combining it with intrastromal air injection. The intrastromal air facilitates tissue removal and also provides some assistance for differentiating the pre-Descemet layer from more superficial stromal layers. He used the pre-Descemet layer as the bed for the FTDG while he did the DALK procedure. He performed large-diameter grafts (9-10 mm) and reported that the astigmatism was usually regular from the first postoperative day. It seems that large-diameter grafts provide enough distance between suture sites and the visual axis to protect it from cold winds of irregularity (Factor 9 above). In my experience, regular astigmatism on the first postoperative day can be obtained with an 8-mm wound area if the center of the trephination wound has been set over the pupil center.

#### **4.3 Using fluid to perform DALK**

58 Keratoplasties – Surgical Techniques and Complications

DALK is indicated for conditions associated with opacification of the corneal stromal tissues over the central area of the cornea while the DM and endothelium are normal and not involved. The opacification may be due to trauma, infections, iatrogenic causes, chemical

DALK is also used for ectatic corneal disorders with normal DM and endothelium, such as keratoconus, keratoglobus, pellucid marginal degeneration, or ectasia occurring after LASIK

The superiorities of DALK over penetrating keratoplasty cannot be overemphasized. However, for obtaining best results, a corneal surgeon must be familiar with different surgical maneuvers used for performing DALK. In this overview of some techniques for

In 1984, Arenas introduced the concept of injecting air into the corneal stroma for performing DALK and the technique was named air-deep lamellar keratoplasty (AD–LKP) (Arenas, 1985). He injected air into superficial corneal stromal tissues at the peripheral cornea. Then a partial-thickness trephination cut of about 400 µm was performed in the resultant emphysematous, white corneal tissue. The superficial corneal layers were removed using sharp blades and deep stromal layers were removed using blunt spatulas until reaching the pre-Descemet level. The movement of the spatulas was centripetally starting at the wound margins and ending at the center or thinnest part of the cornea. He described the pre-Descemet layer as a black and shiny surface devoid of air. The DM was not exposed by this technique; however, after long-term follow-up, the visual results were better than those

performing DALK, some surgical "pearls" will enrich our repertoire of skills.

**4.2 Using shearing and traction force instead of cutting to perform DALK** 

Malbran introduced the peeling-off technique (Malbran, 1966). His concept of a peeling rather than a cutting action for removing the recipient's corneal stromal tissues provided a smoother surface that served as the bed for transplantation. In this technique, the stromal tissues are pooled in a direction that is perpendicular to the corneal surface and a semisharp instrument leads the direction of shearing of tissue through the corneal stromal layers. He also modified his technique by combining it with intrastromal air injection. The intrastromal air facilitates tissue removal and also provides some assistance for differentiating the pre-Descemet layer from more superficial stromal layers. He used the pre-Descemet layer as the bed for the FTDG while he did the DALK procedure. He performed large-diameter grafts (9-10 mm) and reported that the astigmatism was usually regular from the first postoperative day. It seems that large-diameter grafts provide enough distance between suture sites and the visual axis to protect it from cold winds of irregularity (Factor 9 above). In my experience, regular astigmatism on the first postoperative day can be obtained with an 8-mm wound area if the center of the trephination wound has been set

**3. Indications for optical DALK surgery** 

insults, dystrophies, or degenerations.

**4. Surgical techniques** 

**4.1 Using air to perform DALK**

for penetrating keratoplasty.

over the pupil center.

surgery.

Sugita and Kondo introduced the technique of hydrodelamination (Sugita & Kondo, 1997). They injected a balanced salt solution (BSS) into the stromal bed after a lamellar dissection of the cornea. The injection made the stromal collagen fibers swell. A spatula was introduced into the hydrated area and the stroma was dissected by moving the spatula in a fanlike motion. They called this maneuver "spatula delamination." The overlying dissected tissues were removed and the maneuver was repeated until the bare DM was reached in the central cornea. This technique has the advantage of discriminating between normal and pathologic cornea because the pathologic cornea (usually scar) does not swell as well as the normal cornea when being hydrated. This allows the surgeon to determine the depth of the pathology in the corneal stroma.

#### **4.4 Using air and fluid to perform DALK**

Anwar and Teichmann combined the use of air and fluid for planned near-Descemet membrane dissection for performing DALK (Anwar & Teichmann, 2002). They recommended that this technique be used in patients in whom exposing the DM carries a high risk of DM perforation. Such conditions include deep corneal scars involving the DM, patients with keratoconus who have experienced hydrops, those with known DM fragility such as macular dystrophy, and inexperienced corneal surgeons performing occasional lamellar grafts. They created some swelling in the stromal bed after a lamellar dissection by hydrating the stromal collagen fibers. They injected air into the swollen area and removed the resultant emphysematous tissues using Anwar's keratoplasty spatula and repeated the maneuver until they reached the pre-Descemet layer. They described the layer as a semitransparent tissue with the pupil and iris pattern visible through the layer. They concluded that the risk of DM rupture is lower with this technique compared to injecting air alone because the hydrated tissues are thickened and introducing the needle and spatula into the thickened tissue carries a lower risk of violating the DM.

#### **4.5 Using viscoelastic material for performing DALK**

Manche and colleagues used viscoelastic material for separating the DM from the overlying stromal tissues (Manche et al., 1999). They used forceful injection of the viscoelastic material into a pocket incision to make a cleavage plane between the DM and posterior stroma. The pocket was made by a Paufique knife and was parallel to the stromal collagen fibers. Melles and coworkers described the "air-to-endothelium" light reflex as a guide for approaching the DM—stroma interface (Melles et al., 1999). They described a "dark band" between the blade tip and a specular light reflex as the non-incised stromal tissue before reaching the DM—stroma interface. By advancing the blade tip through the dark band the custom-made blade reached the DM—stroma interface and they redirected the blade parallel to the interface to separate the overlying tissues. In 2002, Melles and colleagues introduced the visco-dissection DALK (Melles et al., 2002). They injected viscoelastic material directly over the DM using the air-to-endothelium light reflex as a guide for precise location of the injection for making a DM detachment over an area that was going to be cut by a vacuum trephine. In fact, a TALK procedure has been performed by removing the overlying tissues and using the FTDG.

#### **4.6 Using dye for performing DALK**

Balestrazzi and colleagues used a 0.02% solution of trypan blue for staining the stromal collagen fibers (Balestrazzi et al., 2002). This facilitated the discrimination of the stromal

Manual Deep Anterior Lamellar Keratoplasty 61

Fig. 3. Depth of the trephination wound is checked using a fine toothed forceps.

Fig. 4. Sunny side up sign, red arrows point at a circular furrow encircling the air bubble at

A 27-gauge needle attached to an air-filled syringe is inserted bevel down into the deep stroma in the paracentral cornea as in the big-bubble technique. After air is injected, a paracentesis wound is performed using a stab knife (Eagle Laboratories, Rancho Cucamonga, CA) in a semivertical direction to drain aqueous fluid. A crescent blade (Eagle Laboratories) is used to excise emphysematous stromal tissues as in lamellar keratectomy. The paracentesis wound is widened to 3 mm with the stab knife and the posterior lip of the wound is depressed to drain some aqueous fluid to make the anterior chamber obviously hypotensive. A dry Weck-Cel® sponge is used to depress the cornea. When a big bubble

the DM\_ stroma interface.

fibers from underlying DM. John used indocyanine green and forced hydrodissection for performing TALK (John, 2004). This technique benefits from both hydrating the collagen fibers to create stromal swelling for introducing spatulas into the stromal tissues safely and using dye for discriminating the stromal fibers from the underlying DM.
