28   Corneoscleral Pocket (Hoffman Pocket)

Scleral fixation of intraocular lenses, adjunctive capsular support devices, and intraocular tissues has traditionally been accomplished utilizing sutures. Common to these sutured techniques is the need to rotate, cover, or bury the suture knot that is created to prevent erosion of the overlying conjunctiva and the development of subsequent endophthalmitis.^1,2 Utilization of a corneoscleral pocket for scleral fixation was originally described in 2006 and has many advantages over other techniques for suture fixation.³

First, there is no need for conjunctival dissection, which may sabotage the functioning of filtering blebs or the conjunctiva of future filtering blebs. Due to the elimination of conjunctival dissection and sclera cauterization, the procedure can proceed faster and result in healthier scleral tissue overlying the suture knot that is less likely to degrade with resulting suture knot exposure. In addition, patients appear to be more comfortable and the eyes are less inflamed postoperatively due to the elimination of conjunctival sutures for wound closure.

Construction of the corneoscleral pocket is fairly simple and straightforward. This chapter presents various nuances of the technique to help both the novice and the more experienced surgeon avoid some of the pitfalls that may be encountered during the simple learning curve.

Preoperative Planning

One of the common uses for the corneoscleral pocket is for scleral fixation of subluxed intraocular lens (IOL)/capsular bag complexes. During the initial examination, the patient should be placed in the supine position to ensure that the IOL is still approachable in that position. Even if the IOL appears to move posteriorly when the patient is supine, it is usually still accessible for scleral fixation. In rare instances, the IOL may appear to be accessible when the patient is upright but is completely dislocated when supine. In these instances, coordination with a retinal colleague is usually needed. As part of the preoperative evaluation, the haptics will need to be identified to plan the location of the scleral pockets for fixation. If a capsular tension ring is in place, this simplifies the surgical planning because all 360 degrees of the capsular bag fornix can be utilized as fixation sites. Any preexisting filtering blebs should be identified and avoided if possible. Large filtering blebs that may extend around the interpalpebral limbus can frequently be penetrated toward the bleb periphery by suture passes through an underlying scleral pocket without causing significant bleb leaks or failure of the bleb.

Incision and Dissection

Most surgeries are performed under a peribulbar or retrobulbar block. When two scleral pockets are needed for IOL or bag fixation, these are created 180 degrees apart. Setting a caliper to 13 mm and marking the fixation sites with gentian violet is a useful means of ensuring that the sites are not oblique to each other (Fig. 28.1). Creation of the scleral pockets is best done with a normal intraocular pressure; thus, an anterior chamber (AC) infusion or an AC pressurized with viscoelastic should be avoided at the onset of the pocket construction. Dissecting the pockets, and retrieving the subsequent suture passes is much more challenging when an AC infusion is in place due to the floor of the pocket being compressed against the roof of the pocket.

A 350-µm-deep grooved incision is made at the limbus just anterior to the conjunctival insertion. This can be made with a diamond or metal step blade. The limbal incision is usually 30 degrees in arc length or one clock hour. An opposing limbal groove is made 180 degrees away corresponding to the gentian violet mark on the conjunctiva. Each incision is then dissected posteriorly within the plane of the sclera. Lifting up on the posterior aspect of the grooved incision with a 0.12-mm forceps will aid in the dissection (Fig. 28.2). The dissection is best accomplished with a metal crescent blade, taking care to keep the blade in the plane of the sclera. Bare visualization of the blade through the overlying sclera will ensure that the dissection is not too deep.

Incision Problems

What can go wrong at this point in the procedure? First, the initial groove may not be deep enough. This usually occurs due to a timid surgeon not placing enough downward force on the step knife. Remember, it is guarded, so excessive downward force should not result in a perforation. This can be rectified by resetting the blade to a depth of 400 µn and repeating the groove depth. In regard to the pocket creation, there are two potential pitfalls. The first is cutting too deep during the posterior dissection and entering the suprachoroidal space. When this happens, there is usually a tactile sense of loss of blade resistance. Surprisingly, there is usually not significant bleeding when this happens as long as the dissection is halted before the ciliary body is incised. The pocket dissection is supposed to proceed ∼ 3 to 4 mm posterior to the surgical limbus to ensure that the suture passes are within the dissected sclera. When the floor of the pocket is compromised by a dissection into the suprachoroidal space, the dissection has usually already been performed posteriorly enough so that the procedure can proceed without difficulty. The other potential pitfall is exiting the scleral pocket into the subconjunctival space during the posterior sclera dissection and effectively creating a scleral tunnel. Again, this tends to happen at the end of the dissection, and as long as the suture passes and the subsequent suture knot is covered by the overlying “bridge” of the scleral tunnel, it does not matter if there is an opening into the subconjunctival space (Fig. 28.3).

Fig. 28.1 Radial marks made with gentian violet are 180 degrees apart, marking the position of the center of the pockets. (Inset) A 350-µm deep grooved incision is made at the limbus just anterior to the conjunctival insertion. The limbal incision is usually 30 degrees in arc length or one clock hour.

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