CORNEOSCLERAL POCKET TECHNIQUE
Richard S. Hoffman, MD; I. Howard Fine, MD; Annette Chang Sims, MD; and Janet M. Lim, MD, MBA
Stabilization of a decentered or subluxated intraocular lens (IOL)-capsular bag complex or implantation of a secondary posterior chamber IOL lacking capsular support can be accomplished by means of iris fixation and transscleral fixation through the ciliary sulcus or pars plana. Although iris fixation of decentered IOLs is a popular technique for lens stabilization, late onset of IOL-capsular bag complex subluxation resulting from zonular weakness or dialysis may be more easily repaired with scleral fixation.
Techniques for transscleral fixation include ab interno methods, wherein the suture is passed from the inside of the eye to the external surface, and ab externo methods, in which the suture is initially passed from the external surface. Common to all of the techniques for transscleral fixation is the need to bury, cover, or rotate the knot created for fixation so that conjunctival erosion and subsequent endophthalmitis is less likely to develop.
Scleral fixation of IOLs and adjunctive capsular devices can be performed under the protection of a scleral flap. In 2006, we described a technique allowing for suture knot coverage that avoided the need for conjunctival dissection, scleral cauterization, or sutured wound closure.1 With this technique, a scleral pocket is initiated through a peripheral clear corneal incision. This is followed by full-thickness passage of a double-armed suture through the scleral pocket and conjunctiva with subsequent retrieval of the suture ends through the external corneal incision for tying.
The corneoscleral pocket technique offers a refined method for fixation of IOLs and other intraocular adjunctive devices. We will describe the technique for a late subluxated IOL-capsular complex and secondary implantation of a foldable IOL without capsular support, but it can be employed for any IOL or intraocular device that requires transscleral fixation.
There are currently numerous methods being used for transscleral fixation of IOLs and adjunctive surgical devices.2 Common to these techniques is the requirement for conjunctival dissection and the need to prevent suture knot erosion of the overlying conjunctiva with the ensuing risk of endophthalmitis. Existing methods for knot concealment include covering the knot with a patch graft,3 fascia lata,4 or a triangular scleral flap,3–8 in addition to suturing within a scleral groove,9–11 and suture knot rotation into the eye.12–14 All of these techniques have limitations.
Use of a scleral pocket with hook retrieval of the suture ends can be performed for any procedure requiring transscleral fixation. This includes implantation of secondary IOLs, repair of dislocated IOLs, implantation of adjunctive surgical devices such as Ahmed capsular tension segments and Cionni capsular tension rings, and repair of iridodialyses. This modification of the traditional scleral flap allows simpler creation of a scleral covering, negating the need to rotate suture knots while facilitating needle placement for either an ab interno or ab externo technique.
Figure 30-1. Subluxated IOL-capsular bag complex containing Soemmering ring. Two 30-degree-long (1 clock hour) and 300- to 400-μm-deep clear corneal incisions are made with a diamond step knife 180 degrees apart. These incisions are placed in a meridian that will allow fixation of the lens haptics to the sclera.
Corneoscleral Pocket Technique for Late Subluxated IOL-Capsular Complex
PREOPERATIVE PLANNING
One of the common uses for the corneoscleral pocket is for sclera fixation of subluxated IOL-capsular bags complexes. During the initial office examination, the patient should be placed in a supine position to ensure that the IOL is still approachable in a supine position. Even if the IOL appears to move posteriorly when the patient is supine, it is usually still accessible for scleral fixation. On 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 in order 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 used 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 will be performed under a peri- or retrobulbar block. When 2 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. These incisions are made 180 degrees from each other in a meridian that will facilitate proper final positioning of the IOL optic. The haptics should be incorporated into the suture passes unless a capsular tension ring was previously placed, in which case the capsular tension ring can be secured within the suture passes. The 3 and 9 o’clock meridians should be avoided to prevent damage to the long posterior ciliary arteries. Creation of the sclera pockets is best done with a normal intraocular pressure. Therefore, an anterior chamber infusion or an anterior chamber 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 anterior chamber infusion is in place due to the pocket’s floor being compressed against its roof.
Figure 30-2. Posterior dissection of scleral pockets using a diamond crescent blade. Note the paracentesis originating anterior to the clear corneal incision.
A guarded diamond step knife (05-5027; Rhein Medical) or #64 Beaver blade (376400; BD Medical) is used to make the 30-degree-long (1 clock hour) and 300- to 400-μm-deep incisions just anterior to the conjunctival insertion at the limbus (Figure 30-1). The depth of these incisions can be modified depending on whether more or less flattening is desired in that meridian. Two scleral pockets are then dissected posteriorly from the 2 opposing incisions using a diamond crescent knife (60505; Mastel Precision) or a metal crescent blade (990002 A-OK; Alcon Laboratories, Inc; Figure 30-2). 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.
The pockets are extended approximately 3 mm posteriorly from the clear corneal incisions. Lifting the posterior aspect of the grooved incision with 0.12-mm forceps will facilitate creation of the scleral pocket. Perhaps the most important step in this technique is to ensure that the dissection proceeds posteriorly enough so that the subsequent suture passes are within the area of the dissected sclera. Passing the sutures more posteriorly than the dissected pocket will make retrieval of the sutures through the pocket opening almost impossible. It is for this reason that it is better to dissect too far posteriorly rather than not far enough. Following creation of the pockets, it is also helpful for the novice surgeon to mark the lateral extent of the pockets with a radial gentian violet mark to ensure that the suture passes are not adjacent to the dissected sclera. This is easily accomplished with a Sinskey hook and a gentian violet marking pad.
A 1-mm paracentesis is then created just anterior to each of the clear corneal incisions into the anterior chamber to aid in suture placement. Initiating the paracentesis just anterior to the clear corneal incision instead of within the incision will facilitate the passing of Prolene (Ethicon) sutures since the external opening of the paracentesis can be more easily identified. The paracentesis can also be placed immediately adjacent to the clear corneal incision. These 1-mm paracenteses can be used to place single iris hooks to expose the peripheral capsular bag or concealed IOL haptics. A small quantity of viscoelastic is placed into the anterior chamber through one paracentesis to stabilize the anterior chamber. Viscoelastic may also be placed in the ciliary sulcus underlying the scleral pocket to aid the suture passes.
DOCKING
Suture placement is initially directed toward the haptic that has been exposed through the pupil secondary to the IOL decentration. A double-armed 9-0 Prolene suture on a long curved needle (D8229 CTC-6L; Ethicon) is inserted through the opposite paracentesis and docked into a 25- or 27-gauge needle (Figure 30-3). Passing the suture needle through the paracentesis can be one of the more frustrating steps in this procedure and this is aggravated if the eye is pressurized with an anterior chamber infusion due to forced closure of the paracentesis. Placing a viscoelastic cannula into the paracentesis to open the wound slightly will aid in passing the suture needle into the anterior chamber. In addition, the needle should be moved from side to side when passed through the paracentesis to ensure that no cornea stromal fibers were incarcerated in the needle pass. Once the suture needle is in the anterior chamber, the 25- or 27-gauge hypodermic needle is then passed through the full thickness of the globe corresponding to the dissected sclera pocket, 2 to 3 mm posterior to the surgical limbus. The docking needle should be oriented somewhat parallel to the iris when initially inserted into the eye in order to prevent damage to the ciliary processes. The curved suture needle is then docked into the straight hypodermic needle and will lock into place due to the disparity of a curved needle inside a straight-bore needle. Pulling the hypodermic needle out of the eye once the suture needle is locked will also pull the suture needle out.
Figure 30-3. Docking of the Prolene suture needle into 27-gauge hollow needle above the capsular bag. The suture needle is passed through the 1-mm paracentesis. The 27-gauge needle is passed into the eye through the conjunctiva and the scleral pocket, 2 mm posterior to the surgical limbus.
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