T-FIXATION INTRASCLERAL HAPTIC FIXATION TECHNIQUE

Toshihiko Ohta, MD, PhD

The T-fixation technique is a new surgical technique that allows sutureless intrascleral haptic fixation of a posterior chamber intraocular lens (IOL). This technique achieves safe fixation and does not require complicated intraocular manipulations. In brief, a T-shaped incision is made in the sclera and a 24-gauge microvitreoretinal knife is used for sclerotomy and creation of the scleral tunnel instead of a needle. The T-shaped incision avoids the need to raise a lamellar scleral flap or to use fibrin glue because the haptic can be fixed both inside the tunnel and in the groove, while performing sclerotomy with the microvitreoretinal knife simplifies extraction of the haptic and improves wound closure. Inserting the IOL into the scleral tunnel is also easy because of the wide incision, and there is minimal risk of infection related to scleral exposure of the haptic. Using this technique, IOL decentration and tilt are significantly less prominent than with suture fixation.

When the eye lacks a capsule or the capsule provides insufficient support, implantation of an IOL has been accomplished by transscleral IOL fixation through the ciliary sulcus or pars plana, iris fixation of the IOL, or use of an anterior chamber IOL. However, each of these techniques has problems.¹ Transscleral fixation is associated with several suture-related complications such as IOL decentration, tilt,² suture breakage,³ vitreous hemorrhage,⁴ and endophthalmitis due to suture exposure.⁵ In recent years, IOL implantation with intrascleral fixation of the haptics has become popular.^6–20 We previously developed the Y-fixation technique, an intrascleral haptic fixation technique that did not require large lamellar scleral flaps or fibrin glue (Figure 39-1).^14–17 This technique was a subtype of the glued IOL technique. Next, we devised a modified method called the T-fixation technique because a T-shaped incision is employed (Figure 39-2).¹⁶ A T-shaped incision can be created easily, and fashioning a lamellar scleral flap is not required. Thus, the T-fixation technique is simpler and safer than other intrascleral haptic fixation techniques.

Surgical Technique

Under peribulbar anesthesia, a 5.0-mm conjunctival peritomy is done at the 2 and 8 o’clock positions. A reference marker and T-marker (Duckworth & Kent Ltd) are used for marking (Figure 39-3A). Then, 2 T-shaped incisions are made at 2.0 mm from the limbus and exactly 180 degrees apart diagonally (Figure 39-3B). An infusion cannula or anterior chamber maintainer is inserted. The infusion cannula should be positioned at 4 o’clock to prevent interference with creating the T-shaped incision. Anterior vitrectomy is performed, if necessary. At the intersection of the T-shaped incision, sclerotomy is done parallel to the iris with a 24-gauge angled microvitreoretinal knife (Figure 39-3C), and a scleral tunnel is created parallel to the limbus at the branching point of the T-shaped incision (Figure 39-3D).

Next, a 2.4- to 3-mm keratome is used to make a corneal incision at 11 o’clock, through which a standard 3-piece IOL is implanted by using an injector, with the trailing haptic being left outside the incision. The tip of the leading haptic is grasped with 25-gauge IOL haptic–gripping forceps (Eye Technology; Figure 39-3E), pulled through the sclerotomy, and externalized on the left side. After the leading haptic has been grasped with forceps held in the left hand, the trailing haptic is inserted into the anterior chamber with Gaskin forceps held in the right hand (Figure 39-3F) and positioned on the iris at 8 o’clock (Figure 39-3G). Next, the IOL optic is pushed to the back of the iris and moved to the 2 o’clock position, and its haptic is guided to the center of the pupil by using a push-and-pull hook inserted through the side port at the 1 o’clock position (push-and-pull hook technique; Figure 39-3H).

The tip of the trailing haptic is grasped with 25-gauge forceps, pulled through the second sclerotomy, and externalized on the right side (Figures 39-3H and I). Subsequently, the tip of the haptic is inserted into the scleral tunnel parallel to the limbus with Gaskin forceps, after which the IOL is positioned and centered. Finally, the T-shaped incision is closed with 8-0 polyglactin 910 (Vicryl; Ethicon; Figures 39-3J and K). After the incision has been completely closed and the haptic is embedded in the sclera (Figure 39-3L), a peripheral iridotomy is performed using the vitrectomy cutter after miosis to avoid iris capture of the IOL and the anterior chamber maintainer or infusion cannula is removed. The conjunctiva is closed with 8-0 polyglactin.

Tips for Success

Choosing appropriate forceps to extract the IOL haptics is important for performing surgery safely and without failure. Gabor and Pavilidis⁷ extracted the IOL haptics with end-gripping 25-gauge forceps, but the rounded tips of the instrument may break the haptic during extraction depending on the type of IOL. In contrast, the 25-gauge IOL haptic–gripping forceps developed for the T-fixation technique have tips with a flat inner surface and will not break the haptic when it is grasped regardless of its composition or shape (Figure 39-4). In addition, the short curved shaft of the forceps makes intraocular manipulation easier at the iris level.

Insertion of the trailing haptic into the anterior chamber may be difficult, depending on the material from which it is composed or its shape, and there is a risk of the IOL rotating clockwise with the leading haptic slipping back into the eye. Externalization of the trailing haptic is also associated with a risk of the leading haptic slipping back into the eye.

To prevent the leading haptic from slipping back when performing the T-fixation technique, the leading haptic is grasped with forceps held in the left hand and the trailing haptic is inserted into the anterior chamber with Gaskin forceps held in the right hand. Beiko and Steinert²¹ reported a technique in which the externalized haptic is maintained by a silicone tire without the aid of an assistant. An extremely lightweight serrefine (Geuder AG G-18197) can also be used (Figure 39-5).

Extracting the IOL haptics is an important part of the surgical procedure. It is relatively easy to extract the haptic at the 2 o’clock position, but it is more difficult at the 8 o’clock position. Agarwal et al²² reported a method known as the handshake technique, in which the trailing haptic is extracted using 2 vitreous forceps. However, the haptic can be pulled out with only one vitreous forceps by using the push-and-pull hook technique.

Correct selection of the IOL for intrascleral haptic fixation is also important. In particular, the haptic material needs to be considered carefully. Most 3-piece IOLs have polymethylmethacrylate (PMMA) or polypropylene haptics, but these haptics tend to bend, crimp, and break with the usual manipulations required for intrascleral haptic fixation. This can make it much more difficult to tuck the haptics into the scleral tunnel or dock haptics in a needle. On the other hand, haptics made of polyvinylidene fluoride (PVDF) are stronger, more flexible, and more resilient, and are therefore ideal for intrascleral haptic fixation. It is possible to use IOLs with PMMA haptics, for instance, if the surgeon wishes to keep an existing dislocated 3-piece IOL in the eye, but problems may well arise due to handling brittle haptics that may easily be damaged during surgery.²³ The NX-70 (Santen Pharmaceutical) is one of the IOLs preferred for intrascleral haptic fixation. It has a long total length (13.2 mm) and a large optic diameter (7.0 mm) and is well suited for intrascleral fixation. A larger optic diameter may decrease the risk of iris capture. The haptics of the NX-70 are made of PVDF and are unlikely to be damaged when gripped by forceps. On the other hand, single-piece IOLs with PMMA haptics and single-piece acrylic IOLs are inappropriate for intrascleral haptic fixation.

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