**2. Historical background**

#### **2.1. DALK**

The firts anterior lamellar keratoplasty was performed in 1905 [1]. In the second half of the twentieth century [1], PK became the surgical gold standard to treat the majority of the axial diseases in the cornea. Meanwhile in Colombia at the start of the 1950s, José Barraquer et al. began dissecting two-thirds of the stroma in both the donor and the recipient's cornea [2], but the technique did not gain popularity due to the poor final visual acuity in patients due to irregularities of the interphase.

Beginning in 1984, Eduardo Arenas Archila created the term *deep anterior lamellar keratoplasty* (DALK) by using intrastromal air to dissect the corneal tissue [3]. This technique has evolved over time, and currently surgical techniques achieve the complete separation of the stroma-Descemet interphase with few risks, maintaining the integrity of the Descemet with no stromal residue, which is extremely important to reach a high-quality visual acuity.

In 2002, Anwar developed the *Big Bubble* technique, which is the most widely used one nowadays [2]. This technique allows the separation of the corneal stroma and Descemet with an injection of air into the deep stroma with a #30 cannula after a partial trepanation (80% deep), in this way modifying Archila's technique [4]. The key step in this procedure is the correct injection of air into the recipient's pre-Descemet space to facilitate the removal of the stromal tissue. This technique has been widely accepted worldwide due to its easy reproducibility and high success rate. Nevertheless, it has a steep learning curve that has slowed its adoption [5]. In 2012, Ghanem describes the *pachy-bubble* technique, in which he used transurgical pachymetry to penetrate 90% of the corneal thickness with a diamond scalpel to reach with the air the pre-Descemet space with a higher success rate [6].

#### **2.2. DSAEK**

to trauma, anatomic integrity maintenance, better refractive stability, a quicker rehabilitation and a surgery with fewer risks. Anterior lamellar transplants have evolved into the deep anterior lamellar keratoplasty (DALK), which is the substitution of the entire stroma while maintaining the recipient's Descemet membrane and endothelium. Endothelial transplants have also seen a wide range of changes throughout the years. In the present day, the most widely performed techniques are Descemet stripping automated endothelial keratoplasty (DSAEK), in which the recipient's endothelium and a thin layer of posterior stroma are replaced, and Descemet membrane endothelial keratoplasty (DMEK), in which only the Descemet and endothelium are replaced. Even though lamellar transplants have a wide array of advantages, these techniques are not always offered by the ophthalmologist due to the complexity and the difficult learning curve of the surgical technique, which requires a precise dissection of the corneal anatomic layers. The use of a transurgical optical coherence tomography (OCT) may help the surgeon to visualize the corneal layers and hence increase the rate of success in

The firts anterior lamellar keratoplasty was performed in 1905 [1]. In the second half of the twentieth century [1], PK became the surgical gold standard to treat the majority of the axial diseases in the cornea. Meanwhile in Colombia at the start of the 1950s, José Barraquer et al. began dissecting two-thirds of the stroma in both the donor and the recipient's cornea [2], but the technique did not gain popularity due to the poor final visual acuity in patients due to

Beginning in 1984, Eduardo Arenas Archila created the term *deep anterior lamellar keratoplasty* (DALK) by using intrastromal air to dissect the corneal tissue [3]. This technique has evolved over time, and currently surgical techniques achieve the complete separation of the stroma-Descemet interphase with few risks, maintaining the integrity of the Descemet with no stromal residue, which is extremely important to reach a high-quality

In 2002, Anwar developed the *Big Bubble* technique, which is the most widely used one nowadays [2]. This technique allows the separation of the corneal stroma and Descemet with an injection of air into the deep stroma with a #30 cannula after a partial trepanation (80% deep), in this way modifying Archila's technique [4]. The key step in this procedure is the correct injection of air into the recipient's pre-Descemet space to facilitate the removal of the stromal tissue. This technique has been widely accepted worldwide due to its easy reproducibility and high success rate. Nevertheless, it has a steep learning curve that has slowed its adoption [5]. In 2012, Ghanem describes the *pachy-bubble* technique, in which he used transurgical pachymetry to penetrate 90% of the corneal thickness with a diamond scalpel to reach with

the air the pre-Descemet space with a higher success rate [6].

lamellar transplants.

98 OCT - Applications in Ophthalmology

**2.1. DALK**

visual acuity.

**2. Historical background**

irregularities of the interphase.

In 1956, Tillen introduced the concept of replacing the corneal endothelium by describing the first case of a posterior lamellar keratoplasty [7]. He described how he performed a lamellar dissection of the recipient's cornea and afterward inserted the donor's endothelium to the anterior chamber, suturing it to the recipient's cornea and finally injecting air to apply pressure on the donor endothelium. In 1980, Barraquer modified this technique and trepanated the posterior stroma and sutured to it a posterior lenticule from the donor [8].

Melles is credited with the current success of the endothelial transplant and with the concept of posterior lamellar keratoplasties through a posterior approach [8]. He was the first surgeon to successfully place an endothelial graft to the recipient's stroma without the use of sutures, which allowed better visual results. The procedure was adapted, modified and popularized by Price, which named it *Descemet stripping endothelial keratoplasty* (DSEK). Gorovoy modified this technique by dissecting the donor cornea with a microkeratome, hence the name *descemet stripping automated endothelial keratoplasty* (DSAEK) and is nowadays the most popular technique for endothelial transplants. With the wide acceptance of these techniques, eye banks have begun offering precut donor tissue, facilitating the procedure for surgeons into a onestep procedure.

#### **2.3. DMEK**

In 2002, Melles introduced the concept of DMEK [9]. He reported a simpler method for dissecting the stroma of the recipient, by just removing the Descemet and endothelium and placing the endothelium graft behind the recipient's stroma and injecting air into the anterior chamber to hold the graft in place.
