TRANSSCLERAL GORE-TEX FIXATION OF ENVISTA IOL

Matthew S. Ward, MD

Why do we need another intraocular lens (IOL) fixation technique when, as this book illustrates, many adequate ones are already in use? As is often the case, the more techniques available for fixing a problem, the more likely it is that none of them is perfect. While Gore-Tex (WL Gore & Associates) fixation of the enVista IOL (Bausch + Lomb) is not perfect either, the technique presented here combines many features that are not present in the same combination with other IOL platforms and fixation techniques (Table 32-1).

The sutured enVista technique can be used in a wide variety of complex corneal and retinal applications. Many methods of suturing the enVista to the sclera have been described, including polypropylene fixation with pockets¹ or flaps² and flapless Gore-Tex fixation using docking³ and pull-through⁴ maneuvers. The technique presented here uses an intraocular docking maneuver to preplace the Gore-Tex, after which the sutures are secured to the IOL ab externo prior to insertion.

The MX60 enVista IOL is an aspheric, aberration-neutral, single-piece hydrophobic acrylic IOL available in both spherical and toric platforms. Several design features make this IOL a good candidate for scleral fixation. First, the IOL has an eyelet at each haptic-optic junction that can be used for suture fixation. This fixation is haptic independent, as the suture is used as a guidewire anchoring a free-floating optic (Figure 32-1). This is especially relevant for large eyes where the sulcus diameter may be too large to accommodate intrascleral haptic fixation or suturing to the haptic itself without causing haptic stretch and torsion. Second, the IOL is foldable, enabling a smaller incision than required for fixation of single-piece polymethylmethacrylate IOLs such as the CZ70BD lens (Alcon Laboratories, Inc). A smaller incision may limit surgically induced astigmatism and permit greater anterior chamber stability during surgery. Third, the IOL is made of hydrophobic acrylic material. This is important because multiple reports indicate that hydrophilic lenses such as the Akreos (Bausch + Lomb) are more susceptible to opacification than their hydrophobic counterparts—especially when exposed to intraocular gases after corneal and retinal procedures.^5–13 Because many eyes requiring IOL fixation may require combined or future corneal and/or retinal procedures, it seems desirable to use a material less susceptible to opacification. Third, the enVista (like the Akreos) is aberration neutral and the lens power is uniform from center to edge. As a result, it may be more forgiving to decentration than other aspheric IOLs, though this may not be clinically significant.¹⁴ Finally, this method permits correction of corneal cylinder as a toric option, available for the enVista platform.

In 2018, the enVista toric IOL (MX60T) was approved for use in cataract surgery in the United States. The author has found this lens to be effective in correction of corneal cylinder in patients without capsular support when used off-label for transscleral fixation. The suture fixation axis is directly aligned with the toric marks on the IOL without parallax (see Figure 32-1A). This alignment permits suturing the MX60T without adjustment to operative technique other than ensuring that the IOL is fixated along the steep axis of the patient’s astigmatism.

For many years, polypropylene suture (Prolene; Ethicon) has been used for scleral fixation and has been described for fixation of the enVista.1,2 However, late breakage of this material is a well-known complication,¹⁵ requiring additional surgery for refixation. Gore-Tex is a nonabsorbable polytetrafluoroethylene material available as a 7-0 monofilament suture. This material has high tensile strength and proven longevity. It has been shown to be highly biocompatible with porous microstructure permitting bio-integration.¹⁶ Published use in ophthalmic procedures is extensive, but it is not labeled by the US Food and Drug Administration for ophthalmic use. The CV-8 double-armed suture can be ordered from WL Gore & Associates with a piercing point needle (PT-13*, catalogue number 8M06 for 24-inch length, asterisk indicates double-armed suture). In addition to the long-term stability benefit of Gore-Tex, its bright white color is more easily visualized in the eye, and it lacks the suture memory that can make handling of polypropylene challenging. Thus, Gore-Tex fixation is recommended whenever possible.

There are 2 principal variations of this fixation technique—a 25-gauge docking variation and a 23-gauge pull-through variation (described later). The author prefers a 25-gauge docking variation because this minimizes sclerotomy size and the potential for postoperative wound leak and hypotony. Both variations can be done safely and effectively. The technique can be combined successfully with retinal procedures and corneal transplantation (both endothelial17 and full-thickness keratoplasty). The docking technique can be performed without microinstrumentation. (See Table 32-2 for instrument list.)

Anesthesia

Monitored anesthesia care is recommended for this procedure with use of retrobulbar block to stabilize the eye and ensure comfort throughout the procedure. Anticoagulants should be stopped ahead of surgery to limit risk of intraocular hemorrhage.

A temporal approach is preferred with sutures positioned at the 12 and 6 o’clock positions. Using a toric marker, make limbal marks 180 degrees apart at 12 and 6 o’clock (purple marks in Figure 32-2A). Of course, if a toric IOL is to be used, these marks should be made along the steep axis of astigmatism, and the surgical approach should be adjusted accordingly. Additional marks should be made to mark the 4.0-mm primary incision site (small green marks in Figure 32-2A) and the inferior nasal and temporal paracenteses (large green marks in Figure 32-2A). Next, perform a limited peritomy posterior to each toric mark to expose the bare sclera and cauterize the bed to achieve hemostasis. The eye is now ready for the sclerotomy marks (light blue in Figure 32-2A). These are the most critical marks to ensure successful orientation of the IOL. Please note that the sclerotomies must be oriented radial to the limbus in order to achieve a properly oriented enVista IOL that is parallel to the plane of the iris (see Figure 32-1B). If the sclerotomies are placed tangential to the limbus or 90 degrees opposite the radial marks, then the IOL will orient perpendicular to the plane of the iris (see Figure 32-1C). Using calipers set 1.5 mm apart, measure 1.5 mm posterior to the surgical limbus. Do not ink the caliper tips at this stage, but press firmly on the eye to make a reference point in the sclera. Using the 1.5-mm reference point, ink the caliper tips and make tandem sclerotomy marks radially in line with each toric mark. These will be 1.5 and 3.0 mm posterior to the limbus and approximate the location of the capsular bag in a phakic eye. Use care to make the tandem marks as perpendicular as possible to the limbus as this will reduce the possibility of IOL tilt. Ideally, all 4 sclerotomy marks will line up perfectly in the 90-degree meridian (Figure 32-2B).

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