**2.5 Smooth anterior surface of recipient's tissue**

The smoothest surface of recipient's bed is provided when the bare DM is exposed in the recipient's cornea.

#### **2.6 Clear interface**

The interface between donor and recipient tissues should be washed thoroughly to eliminate the risk of any retained material in the interface, such as viscoelastic material or filaments especially over the optical zone of the cornea.

#### **2.7 Uniform thickness of donor tissue throughout the graft area**

Because the normal corneal thickness gradually increases from the central area toward the peripheral area, great care must be taken to avoid any decentration of the donor tissue when it is cut by a corneal punch. Decentered punching of the donor cornea will result in a donor button that has different thicknesses around the edge of its circumference.

#### **2.8 Uniform thickness of recipient's tissue throughout the graft area**

Many corneal surgeons focus their attention on removing the corneal stromal tissues over the central area to expose the bare DM. They may pay little attention to removing adequate stromal tissues near the trephination wound to make a uniform thickness recipient bed for

Lamellar corneal grafts are classified according to the depth of dissection through the

The dissection plane is from 160 to 400 µm or about 30% to 70% of corneal thickness from

The dissection plane is 400 µm from the surface to the DM. However, from the terminology viewpoint, the term maximum-depth anterior lamellar keratoplasty (MD–ALK) is used when the bare DM is exposed in the recipient's cornea and the term total anterior lamellar keratoplasty (TALK) is used when the bare DM is exposed in the recipient's entire corneal bed and no remaining corneal stromal tissue is present within the trephination wound area. Generally, the wound repair process is accompanied by more scar formation and opacification in the superficial corneal stromal layers compared to the deep corneal stromal layers. So the deeper the dissection plane in the recipient's corneal stromal tissues, the lower

The smoothest posterior surface of the donor tissue is provided when no dissection cuts through the stromal tissues, FTDG is used, and the DM and endothelial cells are wiped out

The smoothest surface of recipient's bed is provided when the bare DM is exposed in the

The interface between donor and recipient tissues should be washed thoroughly to eliminate the risk of any retained material in the interface, such as viscoelastic material or

Because the normal corneal thickness gradually increases from the central area toward the peripheral area, great care must be taken to avoid any decentration of the donor tissue when it is cut by a corneal punch. Decentered punching of the donor cornea will result in a donor

Many corneal surgeons focus their attention on removing the corneal stromal tissues over the central area to expose the bare DM. They may pay little attention to removing adequate stromal tissues near the trephination wound to make a uniform thickness recipient bed for

The dissection plane is up to 160 µm or about 30% of corneal thickness from the surface.

**2.3 Deep plane of recipient's corneal stromal dissection** 

**2.3.1 Superficial anterior lamellar keratoplasty (SALK)** 

**2.3.2 Mid-anterior lamellar keratoplasty (MALK)**

**2.3.3 Deep anterior lamellar keratoplasty (DALK)** 

is the risk of irregularities and scarring in the interface.

**2.4 Smooth posterior surface of donor tissue** 

**2.5 Smooth anterior surface of recipient's tissue** 

filaments especially over the optical zone of the cornea.

**2.7 Uniform thickness of donor tissue throughout the graft area** 

button that has different thicknesses around the edge of its circumference.

**2.8 Uniform thickness of recipient's tissue throughout the graft area** 

recipient's corneal stromal tissues.

the surface.

gently.

recipient's cornea.

**2.6 Clear interface** 

transplantation. It should be emphasized that removing adequate stromal tissues near the trephination wound is as important, if not more important, than doing so in the central cornea. If the task is not performed, the Bowman-to-Bowman opposition of the donor and recipient will occur by excessive force over the sutures and unpredictable visual results will occur when sutures are removed or when sutures lose their tensile strength. The ideal situation is provided by the TALK procedure in which the DM is exposed in the entire trephination wound area. In TALK cases, early removal of corneal sutures can be accompanied with good visual results.

#### **2.9 Minimal irregularities of the anterior surface of the donor tissue over the optical zone**

Given a donor cornea devoid of any preexisting pathology, the corneal sutures will be the major source of irregularities of the anterior corneal surface. In fact, the irregularities originate from the suture sites and radiate over the corneal surface vanishing toward the central area. So the further the distance between a given point over the corneal surface and a suture site, the less the amount of irregularity at the specific point.

If we liken the irregularities that originate from the sutures to the cold winds and the optical zone to a freezing man, it could be said that cold wind of irregularities blow from the suture sites toward the optical zone so the best way to protect the freezing man in the optical zone from the cold wind of irregularities will be to put it at the center of the circle (Figure 1)

Hence, selection of the pupil center as the center of the trephination wound protects the optical zone from adverse effects of the sutures all around the wound.

Fig. 1. Visual axis can be kept away from the sutures at the center of the circle just as the Freezing man keep himself away from the cold winds.

Manual Deep Anterior Lamellar Keratoplasty 59

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

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

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

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

**4.3 Using fluid to perform DALK** 

pathology in the corneal stroma.

and using the FTDG.

**4.6 Using dye for performing DALK** 

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

into the thickened tissue carries a lower risk of violating the DM.

**4.5 Using viscoelastic material for performing DALK** 
