Secondary single-piece toric posterior chamber intraocular lens fixation

Abstract

The intended axis of fixation of a dislocated TECNIS single-piece toric posterior chamber intraocular lens (PC IOL) is identified, and a marker is placed 40 degrees counterclockwise to this axis. A polypropylene suture on a straight needle is passed 2.5 mm posterior to the limbus through a scleral flap at this meridian and into the bore of the needle inserted through a paracentesis at the opposite margin, then the needle is retracted, reinserted, and captured through a second needle inserted through the scleral flap adjacent to the first suture pass, leaving a loop of suture outside of the paracentesis. The haptic of the PC IOL is externalized through another paracentesis made at the scleral flap margin. The loop of suture is pulled into the anterior chamber and out of the latter paracentesis. A cow-hitch knot is fastened around the haptic, which is then repositioned, while the suture is tightened until the PC IOL is in its final aligned position.

Single-piece foldable acrylic posterior chamber intraocular lenses (PC IOLs) are commonly inserted at the time of cataract surgery. With moderate to high amounts of corneal astigmatism, toric PC IOLs are used, requiring not only rotational stability in their standard monofocal versions but also adequate centration when presbyopia-correcting models are used. These lenses may suffer dislocation in addition to toric misalignment in cases, for example, with poor capsular support, loss of capsular bag integrity, subsequent posterior segment surgery, axial myopia, and trauma.^1,2 Many techniques for secondary scleral fixation of 3-piece PC IOLs have been described.^3–5 Although it is generally contraindicated to place single-piece PC IOLs in the sulcus, even when fixated to the iris, due to iris-chafing from the thick haptics resulting in uveitis–glaucoma–hyphema (UGH) syndrome-related complications, methods have been described to reposition single-piece acrylic PC IOLs with both scleral-suturing and direct scleral fixation.^6–13 Some techniques have specifically been described to secondarily fixate toric single-piece PC IOLs.^14,15 Without standardization of the haptic location relative to the toric axis of IOL, the degree of offset required for scleral haptic fixation relative to the toric axis is not universally applicable across IOL manufacturers. In addition, described techniques often require complex intraocular suturing and knot-tying maneuvers. In this study, we modify previously described techniques using cow-hitch suturing for dislocated PC IOLs and repositioning of single-piece Acrysof (Alcon Laboratories, Inc.) toric PC IOLs to address the special needs for centering and rotationally aligning any single-piece TECNIS (Johnson & Johnson Vision) toric PC IOL (monofocal models DIU, ZCU and ZCT, and presbyopia-correcting models DFW, DXW, ZXW, ZXT, ZKU, and ZLU).^14,16

SURGICAL TECHNIQUE

An anterior chamber paracentesis is created followed by injection of intracameral anesthetic and ophthalmic viscosurgical device (alternatively, an anterior chamber maintainer can be used). The intended axis of implantation is identified preoperatively or intraoperatively with a digital registration system (Figure 1, a). A second marker is placed 40 degrees counterclockwise to the intended toric target axis (Figure 1, b). A conjunctival peritomy followed by a partial thickness scleral flap centered at 2 mm posterior to the limbus is performed at this meridian, while a corneal paracentesis is performed both at this margin and 180 degrees opposite along the same axis. Unless a prior pars plana vitrectomy has been performed, a paracentesis can be made approximately 90 degrees apart from the very first one and bimanual anterior vitrectomy performed.

Figure 1.: Intraoperative iris registration system depicts (a) the intended final axis of toric IOL alignment as seen at the completion of surgery and (b) the target axis for haptic fixation at the beginning of surgery measuring 40 degrees counterclockwise to the intended toric axis.

A 10-0 or 9-0 polypropylene suture on a straight needle is passed through the scleral flap 2.5 mm posterior to the limbus and into the bore of a 26-gauge or 25-gauge needle that has been inserted through the opposite paracentesis (Figure 2, a). The needle is retracted out of the paracentesis, then reinserted, and captured through a second 26-gauge or 25-gauge needle that has been inserted through the scleral flap adjacent to the first suture pass (Figure 2, b). The needle is retracted through this scleral flap leaving a loop of suture outside of the second paracentesis.

Figure 2.: a: 10-0 polypropylene suture on a straight needle inserted under the scleral flap and lodged in the bore of a 25-gauge needle entering the opposite corneal paracentesis, as it is being directed out of the paracentesis, followed by (b) the 10-0 polypropylene suture straight needle reinserted through the corneal paracentesis aiming to lodge it into the bore of the same 25-gauge needle inserted through the scleral flap and 1 mm apart from the initial entry point of the suture needle.

The dislocated haptic of the PC IOL is freed from its position in the capsular bag or sulcus space, raised into the anterior chamber, and externalized through the first paracentesis. The loop of suture is then retracted into the anterior chamber and out of the first paracentesis. A cow-hitch knot is fastened around the extruded haptic and tightened at a distance of 1 mm from its distal end, which is then pushed back into the anterior chamber while pulling on the suture ends to reposition the haptic in the sulcus posterior to the iris and in its final position (Figure 3). Tension can be adjusted on the external suture knot before tying it to fine-tune the centration and rotational alignment of the PC IOL. The suture ends are then tied and cut, and the scleral flap and conjunctival peritomy sealed with tissue glue (Video 1 demonstrating the technique with a toric presbyopia-correcting DFW225 IOL, available at https://links.lww.com/JC9/A371).

Figure 3.: A cow-hitch knot is created from the externalized free loop of 10-0 polypropylene suture and looped around the end of the haptic while temporarily extruded from the same corneal paracentesis.

DISCUSSION

Toric PC IOLs are standardized and approved for implantation in the capsular bag. When capsular support is not available, techniques for off-label fixation of these PC IOLs are made challenging by the need for rotational alignment of the PC IOL in addition to the need for proper centration and tilt mitigation. Here is demonstrated a simple technique for repositioning and aligning a TECNIS single-piece toric PC IOL. This technique avoids complex intraocular suturing and knot formation. Whereas previous techniques have described refixation of single-piece toric PC IOLs, either the degree of toric IOL haptic fixation has not been specified or has been described in models of IOLs other than that used here.

Various PC IOLs use different degrees of haptic offset from their steep toric axis. As such, techniques for secondary fixation of these haptics cannot be standardized across different models. An additional challenge in alignment of the toricity of the IOL with the intended axis of astigmatic correction is based on the fact that the PC IOL is designed for intracapsular bag implantation. When capsular support is not available, and when the haptics are fixated to the sclera, the degree of haptic offset from the toric axis changes based on added tension to the haptics in their stretched, scleral-fixated position. The average capsular bag diameter is smaller than the ciliary sulcus diameter, especially when considering the natural shrinking of the diameter of the bag during the postoperative healing period.^17,18

Figure 4, a demonstrates the degree of offset in the standard position of the TECNIS single-piece toric PC IOL, whereas Figure 4, b presents the degree of offset that would be expected when the haptics are stretched as with scleral fixation. When using the cow-hitch suture, the loop conveniently rests at the distal end of the haptic just where it slightly thickens, inducing the haptic pulling that results in this stretched PC IOL configuration. The specified offset of 40 degrees in this article, therefore, results in correct alignment of the astigmatic axis of the TECNIS toric PC IOL with the steep axis of corneal astigmatism (Figure 4, b). The additional use of a digital marking system helps ensure the accurate final position of the PC IOL, while tension can be adjusted on the external suture knot before tying it to fine-tune the centration and rotational alignment of the PC IOL.

WHAT WAS KNOWN

• Repositioning of single-piece acrylic toric PC IOLs has been described with a variety of techniques that involve either direct scleral fixation or intraocular suturing maneuvers.

WHAT THIS PAPER ADDS

• This modified cow-hitch technique is an easily reproducible method for centering and rotationally aligning a TECNIS single-piece foldable acrylic toric PC IOL when targeting a 40-degree counterclockwise offset in haptic fixation relative to the desired toric axis.

Figure 4.: a: A standard TECNIS toric PC IOL shape with a 40-degree toric axis offset bisecting the haptics, (b) simulated stretched haptics of the scleral-fixated toric PC IOL shape with the 40-degree toric axis offset leading to the distal bulb of the haptic and thus the ideal location for cow-hitch suture fixation.