Corneoscleral pocket technique used for fixation of subluxed IOL-capsular bag complex
Surgeons explain why the technique has several advantages for scleral fixation.
Stabilization of the decentered or subluxed 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, in which 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 are less likely to develop.
Scleral fixation of IOLs and adjunctive capsular devices can be performed under the protection of a scleral flap. In 2006, Hoffmann described a technique that allowed for suture knot coverage and avoided the need for conjunctival dissection, scleral cauterization or sutured wound closure. 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.
My guests in this column are Richard S. Hoffman, MD, and his colleagues.
Amar Agarwal, MS, FRCS, FRCOphth
OSN Complications Consult Editor
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 subluxed IOL-capsular complex, secondary implantation of a foldable IOL without capsular support and iridodialysis repair, but it can be employed for any IOL or intraocular device that requires transscleral fixation.
There are several advantages of the scleral pocket technique for scleral fixation. First, a larger surface area can be created for suture passes than with triangular scleral flaps or scleral grooves. This allows the suture needles to exit anywhere inside the large dissected pocket as long as they are at the appropriate distance from the surgical limbus (0.5 mm to 1 mm for ciliary sulcus fixation). This is especially useful when utilizing an ab interno approach.
Second, dissection of the scleral pocket initiated from a clear corneal incision avoids the need for conjunctival dissection or scleral cautery. This should induce less discomfort in patients undergoing procedures with topical anesthesia in which unforeseen complications may necessitate use of scleral-fixated lenses or fixated capsular bag prostheses. The dissection of the distal scleral pocket is also easier to perform than a triangular flap in the distal location because the dissection can proceed directed away from the surgeon in a slightly “downhill” direction. In addition, the procedure may be expedited relative to a triangular flap technique because conjunctival dissection is avoided and sutured wound close is unnecessary.
Finally, less astigmatism may be induced than would occur with the placement of two radial sutures through each of two opposing triangular flaps in the same meridian. Although two opposed 30° vertical clear corneal incisions have a small flattening effect in the meridian of placement, the small arc length and relatively superficial depth compared with traditional limbal relaxing incisions induce very little astigmatic effect, and this can be modified by using more superficial 300-µm incisions, depending on the desired astigmatic result.
Corneoscleral pocket technique
Calipers dipped in gentian violet are used to mark the locations for the peripheral clear corneal incisions. These incisions are made 180° 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. A guarded diamond step knife (#05-5027, Rhein Medical) or #64 Beaver blade (#376400, BD) is used to make the 30° long (1 clock hour) and 300- to 400-µm-deep incisions just anterior to the conjunctival insertion at the limbus (Figure 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 dissected posteriorly from the two opposing incisions using a diamond crescent knife (#60505, Mastel Precision) or a metal crescent blade (990002 A-OK, Alcon Laboratories) (Figure 2). The pockets are extended approximately 3 mm posteriorly from the clear corneal incisions. A 1-mm paracentesis is 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 sutures because 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 utilized to place single iris hooks to expose the peripheral capsular bag or concealed IOL haptics.
Images: Hoffman RS and colleagues
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. Suture placement is initially directed toward the haptic that has been exposed through the pupil secondary to the IOL decentration.
A 25- or 27-gauge needle is passed through the conjunctiva and the full thickness of the scleral pocket 1 mm posterior to the surgical limbus. This needle is inserted into the eye, behind the iris and in front of the capsular bag far enough to allow visualization of the beveled tip. A double-armed 9-0 Prolene suture on a long curved needle (D-8229 CTC-6L, Ethicon) is inserted through the opposite paracentesis, docked into the 27-gauge needle (Figure 3), and both are removed externally through the scleral pocket and the conjunctiva. The 27-gauge needle is then passed again through the conjunctiva and the full thickness of the scleral pocket 1 mm posterior to the surgical limbus and 1 mm to 2 mm adjacent to the first pass of the needle. The 27-gauge needle is inserted into the eye but behind the capsular bag equator. The needle perforates the capsular bag central to the IOL haptic and passes completely through the posterior and anterior capsule. The second arm of the double-armed Prolene suture is passed through the opposite paracentesis, docked with the 27-gauge needle, and both are again removed through the full thickness of the eye (Figure 4).
At this point, all suture passes are through the full thickness of the sclera at the ciliary sulcus. By removing the needles from all suture passes, each suture end can then be retrieved through the scleral pocket opening by passing a Sinskey hook into the pocket and pulling the trailing suture end through the corneal incision so that the sutures are now passing through the corneal incision, through the floor of the scleral pocket (1 mm posterior to the surgical limbus) and into the eye through the ciliary sulcus. When retrieving the sutures through the corneal incision, holding the other suture of the double-armed pass with forceps will prevent inadvertently pulling that suture end out of the eye (Figure 5). Tying of the suture ends recenters the IOL and allows the knot to be concealed as it slides under the protective roof of the scleral pocket.
The same technique can be performed on the opposite haptic utilizing the second scleral pocket and the opposing paracentesis (Figure 6). An iris hook can be placed in the first paracentesis to aid in visualization of the capsular bag equator and lens haptic for the second fixation site. Suturing of the scleral pockets is not necessary. Viscoelastic can be removed by injecting Miochol-E (acetylcholine chloride, Bausch + Lomb) into the anterior chamber while depressing the posterior lip of one of the paracenteses or with bimanual irrigation and aspiration cannulas inserted into each of the two paracenteses.