Ординатура / Офтальмология / Английские материалы / Corneal Endothelial Transplant (DSAEK, DMEK & DLEK)_John_2010

Introduction

The earliest evidence of image magnification utilizing a magnifying glass dates back to the Book of Optics that was published by Ibn al-Haytham (Alhazen) in the year 1021. Since 1860 loupe magnification was used for surgical intervention. However, it was not until the year 1921, when Nylén from Sweeden transformed an ordinary laboratory microscope into a monocular operating microscope for ear surgery, that the first operating microscope was introduced.1,2 In the same year Holmgren first used the binocular operating microscope.1 These technological advances led to the development of true microsurgery. Ophthalmologists were the second group of physicians to use microscope in the operating theatre during the years 1940-1950.1 Since 1953, highly professional operating microscopes were made available and in the 1960s developments in the areas of microsurgical techniques, microinstruments and suture materials took place.

The modern day operating microscope provides a wide range of magnifications and has the capability of zoom function, all of which are controlled by the foot pedals. This allows the surgeon’s hands to be free to perform surgery. This change in the way eye surgery was done forced the eye surgeons to use all four limbs during surgery. Thus, the introduction of the binocular operating microscope resulted in a paradigm shift in the way ophthalmic surgeons performed eye surgery. The operating microscope has served us well over several decades. During this time much of the surgical procedures in the anterior segment required only gross, full-field view with depth perception for both corneal and cataract surgeries. This scene is currently in a process of continual change as surgeons are slowly moving away from full-thickness, penetrating keratoplasty (PKP) to selective tissue corneal transplantation (STCT).3-5 STCT selectively replaces diseased parts of the cornea with similar donor tissue, while retaining the healthy portions of the patient’s cornea. With the increasing use of lamellar keratoplasty (LKP) techniques, the corneal surgeons require the ability to visualize the corneal thickness, and perceive the various corneal depths while doing surgery. In the absence of a cross-sectional view of the cornea, surgeons in the past have injected air into the anterior chamber (AC) and viewed the dark band between the reflective surface of the airbubble within the AC and the corneal surface blade edge, as the estimate of the remaining corneal thickness. This technique is laborious, and at best a rough estimate of the corneal thickness.

At the present time we need the ability to directly view the corneal thickness in real-time with the aid of a slit-

view, much like the way we examine the anterior segment in a clinical setting. In order to meet this surgical need, the surgeon may consider the use of an intra-operative surgical slit-lamp. Over time, the use of an intra-operative surgical slit-lamp would possibly become the gold standard for ophthalmic microsurgery. Other areas of continued development in surgical viewing of the operative field include the ongoing experiments with video-assisted systems to further miniaturize the instruments for magnification and to gain a more comfortable working position for the surgeon.

In this chapter, various surgical cases are presented to illustrate the use of an intra-operative surgical slit-lamp, demonstrating the usefulness of such a devise in corneal and anterior segment surgeries.

Surgical Cases

Case 1 (Figure 10-1)

In Descemet’s stripping automated endothelial keratoplasty (DSAEK), there is a surgical concern as to fluid being trapped within the donor-recipient interface that may contribute to post-operative donor disc detachment. In an attempt to eliminate potential fluid within this interface, various techniques have been described. One technique is to create “venting” incisions on the recipient cornea up to, and inclusive of, the interface without detaching the donor corneal disc. Four such incisions are usually made per eye. These incisions are routinely made on all cases undergoing DSAEK, since the interface is not visible with the conventional view provided by standard operating microscopes. With the use of a surgical slit-lamp the interface is clearly visible (Figure 10-1) and there is no fluid seen in the donorrecipient interface. Hence, no venting incisions are required. Surgical slit-lamp is beneficial in DSAEK surgery.

Case 2 (Figure 10-2)

Patient was referred by his ophthalmologist with a large Descemet’s membrane (DM) detachment that occurred as a complication of clear cornea, phacoemulsification. This DM detachment resulted in significant corneal edema (Figure 10-2) and blurred vision following the cataract surgery. Large air bubble was used to attach the DM to the inner stromal surface of the patient’s cornea (Figure 10-2). Lindstrom roller is used to compress the corneal dome to facilitate a uniform attachment of the DM to the inner corneal stroma (Figure 10-2). Unlike the conventional, full-field view that does not allow adequate visualization of the DMstromal interface, the slit-view of the surgical slit-lamp

confirms good, uniform attachment of the DM in this case (Figure 10-2) and intra-operative clearance of the corneal stromal edema that is visible by the decreasing stromal thickness seen with the surgical slit-beam (Figure 10-2).

lens remnants without damaging the posterior lens capsule (Figure 10-3). The surgical slit-lamp view helps to assess this region during surgery (Figure 10-3).

Case 3 (Figure 10-3)

Two weeks following an uneventful, clear cornea phacoemulsification, cortical lens remnants left behind in the superior, equatorial portion of the lens capsule migrated inferiorly and presented as cloudy lens material in the retrointraocular lens (IOL) potential space between the IOL and the posterior lens capsule, causing blurred vision. A bimanual surgical technique is used to clear the cortical

Case 4 (Figure 10-4)

Figure 10-4 displays the surgical steps in managing pseudophakic bullous keratopathy caused by a closed-loop IOL. The procedure included a PKP, removal of the closedloop IOL, automated, anterior vitrectomy, and scleralfixated Posterior Chamber IOL (Figure 10-4). The junction between the donor corneal graft and the rim of the recipient cornea is important, since there may be a step, where the edge of the donor graft may be slightly higher as compared

to the edge of the recipient cornea causing surface irregularities. Additionally, very tight sutures may also contribute to irregularities at this donor-recipient circular junction. The slit-beam allows proper evaluation of this junction. In this case, a uniform, smooth junction is seen (Figure 10-4) confirming a good end-point for this surgery.

Case 5 (Figure 10-5)

This is a case of advanced keratoconus with significant corneal thinning, apical cone scarring, and contact lens failure (per history) and the patient was referred for surgical management. The surgical options include full-thickness PKP, use of an intra-stromal Intacs (Addition Technology,

Inc.), and LKP. Of these three surgical options, LKP may be considered as the best option, since the patient’s endothelium is retained, and no prosthetic device is introduced into a very thin cornea. However, total lamellar keratoplasty (TALK) is a very challenging surgical procedure, where the surgeon needs to dissect the cornea and remove all the corneal stroma from a very thin cornea and not cause any tear or DM perforation during the TALK procedure. This challenging technique becomes even more difficult with the full-field view provided by the conventional, operating microscopes. The surgical slit-lamp provides direct visualization of the corneal thickness throughout the surgical procedure and helps prevent or decrease the chance of DM perforation during TALK procedure (Figure 10-5).

Case 6 (Figure 10-6)

DSAEK is soon becoming the preferred surgical procedure over a PKP in the surgical management of corneal endothelial decompensation. However, DSAEK can also result in endothelial graft rejection and graft failure. This is a case of DSAEK graft failure following graft rejection that did not fully resolve with standard medical management. Hence, a disc-exchange is required that is superior to a full-thickness PKP. Figure 10-6 demonstrates the surgical steps in this case of DSAEK disc-exchange. The surgical slit-lamp view aids in fully assessing the donor-recipient interface and no “venting” incisions on the recipient cornea is required (See also Figure 10-1).

Case 7 (Figure 10-7)

This is an example of an intra-operative donor disc that “flipped” or unfolded in the wrong direction during a DSAEK procedure resulting in the donor endothelium facing the host, inner corneal stroma (Figure 10-7). Removal of the donor disc and reinsertion with the proper orientation is required. It may be difficult in such a case to clearly confirm the endothelial surface from the stromal surface using the full-field view afforded by conventional operating microscope. Here, the surgical slit-beam clearly identified the endothelial surface from the stromal surface and on evaluating the cut-edge of the donor disc the cut margin of the DM is clearly seen, that further confirms the endothelial side of the donor disc (Figure 10-7).

Case 8 (Figure 10-8)

This is an extremely rare case presentation for surgical management. This patient had undergone an uneventful artificial cornea, namely, a keratoprosthesis. After about 6 months following the surgery the patient sees a cornea specialist with a history of redness and eye pain. The patient is then referred with a bandage soft contact lens. On clinical exam, the patient had no cornea and no keratoprosthesis. Removing the bandage contact lens provided direct visualization of the iris surface and the pupil with vitreous in the papillary space. Patient’s eye was immediately patched after antibiotic application and he received intravenous prophylactic antibiotics and underwent emergency eye surgery (Figure 10-8). The surgical slit-beam aided the surgical procedure especially during the iris membrane peeling and anterior segment reconstruction and a large diameter PKP (Figure 10-8).

Case 9 (Figure 10-9)

Patient had a traumatic corneal laceration with lens rupture and secondary cataract. The primary corneal repair was performed by the referring ophthalmologist. There was a very large anterior lens capsular tear that did not extend to the posterior lens capsule. Surgical slitlamp view greatly facilitated the surgical management

(Figure 10-9).

Surgical Pearls and Tips

Take advantage of the surgical slit-lamp when available. Use both the broad-beam and narrow-beam as needed, along with the retro-illumination, by changing the angle of the beam to facilitate viewing various anterior segment tissues during surgery as demonstrated in the case examples provided above in this chapter.

Conclusion

The use of an intraoperative surgical slit-lamp provides the visualization that is needed for the present day newer, corneal dissection techniques and anterior segment surgery. STCT of the cornea requires meticulous lamellar dissections of the cornea without tearing or perforating the DM during such procedures. The surgical slit-lamp is helpful in these advanced corneal and anterior segment surgical procedures.

References

1. Haeseker B: [Microsurgery, a ‘small’ surgical revolution in the medical history of the 20th century]. Ned Tijdschr Geneeskd 1999;143:858-64.

2. Tamai S. History of microsurgery – from the beginning until the end of the 1970s. Microsurgery 1993; 14:6-13.

3. John T. Surgical Techniques in Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006:1-687.

4. John T. Step by Step Anterior and Posterior Lamellar Keratoplasty. New Delhi, India: Jaypee Brothers Medical Publishers; 2006:1- 297.

5. JohnT.Selectivetissuecornealtransplantation:agreatstepforward in global visual restoration. Expert Rev Ophthalmol 2006;1:5-7.