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Recovery Techniques in Deep Anterior Lamellar Keratoplasty


Key Concepts

  • The cannula “big bubble” (BB) technique and the bubble test lessen the possibility of deep anterior lamellar keratoplasty (DALK) intraoperative complications.

  • If the air BB fails, the air-visco bubble (AVB) technique can be used.

  • A manual dissection can be employed if bubble separation techniques are not successful.

  • Rescue techniques for cases in which there are intraoperative tears or ruptures in the Descemet membrane differ based on the size and location of the tear, and primarily based on the adopted surgical techniques

  • Conversion to penetrating surgery can be avoided in the majority of cases.

  • The curvature disparity between donor graft and the recipient bed is an important factor when repairing Descemet membrane tears in predescemetic DALK.

Introduction

Deep anterior lamellar keratoplasty (DALK) should be considered the first surgical choice in all corneal stromal diseases with healthy endothelium. , Despite numerous valuable DALK techniques that have been described (see Chapter 120 ), penetrating keratoplasty (PK) conversion still remains an unsolved problem, which may occur if a surgeon struggles to reach a sufficiently deep plane or after intraoperative rupture of the Descemet membrane (DM). The rate of PK conversion ranges between 0% and 60% and is often related to surgeon experience and to the effective management of intraoperative DM ruptures.

DALK recovery techniques are designed to avoid conversion to PK and to bestow all the advantages of this technique on the patients.

Standard Techniques And Learning Curves

A standard approach is important for safety during the learning curve. Consequently, the first goal should be obtaining a macroscopic DM exposure (it has been demonstrated that there is a very thin layer of stroma in the recipient bed of what was thought to be a descemetic DALK [dDALK], now reclassified as subtotal anterior lamellar keratoplasty [STALK]) because it allows faster visual recovery and renders the surgeon confident that he/she has performed optimal surgery (see Table 120.1 ). ,

The “big bubble” (BB) technique is the most commonly used strategy for achieving this result, and, specifically, the use of a dedicated blunt cannula ( cannula BB technique ) (see ) instead of a needle seems to represent the safest way to accomplish it. In a study on 507 eyes affected by keratoconus, the use of a smooth cannula resulted in a successful BB in 82% of cases, whereas the use of the needle only in 60% ( P < .01).

Several surgical strategies may be employed if the BB technique fails.

Repeated Air Injections

When the BB fails, some surgeons suggest further attempts at air injection. Achievement of BB with a second air injection implies that the depth provided by the first insufflation was insufficient.

Air-Visco Bubble Technique

Air-visco bubble (AVB) technique (see ) is a technique designed by Sarnicola et al. for cases where BB formation has failed. When air dissection does not result in the formation of the BB, a superficial keratectomy is performed with a golf knife. A deeper tunnel is created in the stroma using a blunt spatula. The same cannula used for the air injection is then attached to a viscoelastic-filled syringe and viscodissection is used as a second strategy for separating the DM from the corneal stroma. , , In a study over 507 eyes, this combined (AVB) technique rescued approximately 14%–15% of air BB failure and 12% of failing STALK procedures, increasing the success of BB from 82% of cases in which BB had been achieved with the air cannula technique to a total of 94% of STALK procedures.

A paracentesis should be performed after attempting to obtain an air BB and before attempting the AVB; this may be helpful for some reasons. The air flow is usually fast and not easy to control when creating an air big-bubble, and DM rupture can occur if the air reaches the paracentesis, especially in BB type 2 cases where the BB starts from the periphery and has a larger diameter. , Therefore we prefer to perform a paracentesis after formation of the air BB. On the contrary, formation of a viscobubble is slower and more controllable, because of the high density of the viscoelastic, resulting in a lower risk of accidentally reaching a preexisting paracentesis. Moreover, softening the eye after bubble formation through a paracentesis creates more space into the anterior chamber, and it determines expansion of the volume of both air bubble and viscobubble. Enlargement of the viscobubble is usually bigger due to the higher pressure exerted by the dense viscoelastic compressed inside the bubble. If the viscobubble reaches the paracentesis, it can cause enlargement of the incision and a DM break.

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