**6. Overview of optical coherence tomography (OCT)**

The OCT is based on the principle of low coherence interferometry to measure distances. A light source is used, typically a superluminescent infrared diode with a wavelength between 830 and 1325 nm. OCT has revolutionized clinical ophthalmology, and its development continues providing opportunities for a better diagnosis and even management of eye diseases. Originally introduced in the 1990´s at the Massachusetts Institute of Technology in 1991 as a technique for noninvasive transverse imaging of biological systems, the image of the retina was the first application of this technology [11]. OCT devices have undergone modifications in their original technique to see and measure anterior segment structures such as the cornea, iris, and the lens [12]. In 1994, Izatt described the use of OCT for the anterior segment with a resolution close to histological level [13]. Since then, it has been used for the diagnosis and

**Figure 5.** OPMI LUMERA & RESCAN 700 microscope, where OCT images can be observed in real time.

Transplant and Research, Tampa, Florida, USA). In this technique, balanced saline solution is injected to achieve separation of the Descemet membrane (**Figure 4**). Currently, it is possible to get the tissue prepared and preloaded by the staff of some eye banks, which facilitates the

Once the donor tissue is obtained, surgery is performed on the recipient, initiating with the introduction of trypan blue to improve Descemet visualization, then the circular descemetorhexis of an average of 8.25 mm is performed. The Descemet can be extracted using the irrigation-aspiration piece of the phacoemulsification equipment, through a previously performed 3 mm incision. An iridectomy is performed in MVI, and the donor tissue is introduced and unfolded with delicate hydraulic and pressure-counter-pressure maneuvers, finally introducing the air/gas in the anterior chamber once the correct unfolding of the graft

Currently, the number of surgeons performing DMEK is on the rise because of its better visual

The OCT is based on the principle of low coherence interferometry to measure distances. A light source is used, typically a superluminescent infrared diode with a wavelength between

procedure and eliminates the risks of tissue preparation in the operating room.

**Figure 4.** Blister technique for the isolation of corneal Descemet-endothelium prior to a DMEK surgery.

has been ensured. The eye must be completely sealed with or without sutures.

The DMEK procedure has some complications including:

• endothelial dysfunction secondary to surgical trauma

**6. Overview of optical coherence tomography (OCT)**

• lack of adherence of the donor tissue • foldings or tears in the donated tissue

acuity results when compared to DSAEK.

• inverted positioning of the tissue

• pneumatic pupillary block

104 OCT - Applications in Ophthalmology

**Figure 6.** OPMI LUMERA & RESCAN 700 microscope, OCT images can be appreciated for all members of the surgical team.

management of various corneal conditions. Now that it is one of the most important diagnostic tests in ophthalmology, it is natural to use this technology in the operating room, as it provides a unique feedback mechanism in real time and helps facilitate the achievement of surgical objectives.

trepanation seems to be useful to determine if the depth is adequate or there is a need for

Intraoperative OCT in Lamellar Corneal Transplants (DALK, DSAEK, DMEK)

http://dx.doi.org/10.5772/intechopen.79322

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Once air is injected to create the bubble that will separate the Descemet membrane and stroma, OCT images are captured to verify the extent of the dissection, and to check whether it reached the trepanation mark limit. These images will help the surgeon assess if there is risk of perforation or if there exists an inadequate separation of the stroma and the Descemet

In cases of poor visibility secondary to injected intrastromal air, the OCT helps to see the extension of the big bubble in the anterior chamber to ensure it is complete and to prevent

**Figure 8.** The red arrow points to the Descemet membrane separated from the stroma by air forming the big bubble.

**Figure 9.** Descemet membrane (red arrow) returning to its original location. This is after the perforation of the stroma.

further dissection to reach the ideal depth for an air injection.

perforation when removing the stroma (**Figure 11**).

membrane (**Figures 8**–**10**).

The authors use the OPMI Lumera® 700 and RESCAN™ microscope from Zeiss (**Figures 5** and **6**), and this microscope includes an integrated OCT system, which optimizes the procedure of deep anterior lamellar keratoplasty and endothelial keratoplasty.
