Melina I. Morkin, MD and Naveen K. Rao, MD
There is no consensus on what intraocular lens (IOL) implantation technique is best in the absence of capsular support. This textbook reviews numerous alternative approaches, which include anterior chamber, iris-fixated, and sutured and sutureless scleral-fixated IOLs. Each of these methods has distinct advantages and challenges. In cases that preclude anterior chamber implantation or iris fixation, scleral support techniques must be undertaken.
The double-needle intrascleral flanged haptic fixation technique described by Shin Yamane et al1 offers multiple advantages compared to other intrascleral haptic fixation methods. For instance, suture erosion and breakage remain long-term concerns with suture-fixated IOLs and this increases the risk of lens dislocation and need for repeat surgery. In one study, up to 27.9% of 10-0 polypropylene-sutured IOLs developed suture breakage after 6 years of follow-up.2 As a result, the off-label use of nonabsorbable polytetrafluoroethylene sutures has gained popularity for scleral suturing due to its higher tensile strength and durability.3 Similarly, to overcome the risks of suture-related complications, a sutureless intrascleral IOL implantation technique4 assisted with fibrin glue for fixation5 was developed by Agarwal et al. After creating conjunctival peritomies, partial-thickness scleral flaps are created, and 23- to 25-gauge needles or trocars are used to create the sclerotomies under these flaps. To minimize the risk of postoperative hypotony, a double-needle technique with 27-gauge sclerotomies was described by Yamane et al.6 This approach was then further optimized by the same group through the use of 30-gauge scleral passes. The significantly smaller diameter sclerotomies offered better sealing capabilities and therefore eliminated the need for suture or glue-assisted sclerotomy closure.1 Firm haptic fixation was achieved by creating flanges on the 2 haptic ends with low-temperature cautery.
The glued IOL technique requires conjunctival peritomies on either side of the limbus. In eyes with prior conjunctival surgery (glaucoma, pterygium, retina, or ruptured globe surgeries), preexisting scarring can make the creation of a conjunctival peritomy more challenging. In these eyes, the transconjunctival flanged haptic fixation approach may be more suitable.
The aforementioned benefits of the Yamane double-needle technique can be somewhat offset by the steep learning curve associated with a surgeon’s initial cases. Therefore, we aim to offer practical recommendations that we have found effective in adopting the technique. We also provide surgical pearls to help avoid common mistakes and complications that beginning surgeons may more commonly encounter.
Before attempting this new method, we recommend that the surgeon first learns intrascleral haptic fixation with the glued IOL technique (Agarwal), and then transitions to the double-needle flanged haptic method (Yamane). It is certainly easier to hand off a haptic between 2 micrograspers as in the glued IOL technique than it is to dock a haptic into the lumen of a small-gauge needle as in the flanged haptic technique. In addition, the glued IOL method tends to make IOL centration easier, because there is direct visualization of the sclerotomy position. With the flanged haptic technique, the length of the needle tunnel through the sclera and the precise location of the internal needle entry site impact IOL centration but cannot be directly visualized.
What is the best IOL to use for the flanged haptic fixation technique? While most 3-piece IOLs have polymethylmethacrylate (PMMA) or polypropylene haptics, these materials tend to bend and break with the usual manipulations required for intrascleral haptic fixation. This can make tucking the haptics into the scleral pockets and docking the haptics into needles much more difficult. Instead, IOLs with haptics made of polyvinylidene fluoride (PVDF) are sturdier, more flexible, and much more resilient, and are therefore ideal for intrascleral haptic fixation. It is possible to use IOLs with PMMA haptics as would be desirable when refixating an existing dislocated 3-piece IOL. However, the surgeon should be prepared to deal with the possibility of brittle haptics that may break during surgery, either along the shaft of the haptic or at the haptic-optic junction. A new back-up IOL should be available in case IOL exchange is needed.
Another important point to consider is that silicone IOLs have been reported to become opacified during vitreoretinal procedures, particularly when silicone oil is used. As intrascleral haptic fixation is typically performed in complex eyes and there is a possibility of subsequent vitreoretinal surgery, silicone IOLs may not be the best choice. Hydrophobic acrylic 3-piece IOLs are therefore recommended.
To make the flange of the haptics, it is of paramount importance to use low-temperature cautery because high-temperature cautery is too hot and can shorten the haptics significantly. While PVDF haptics tend to form a nice mushroom-shaped flange, PMMA haptics have been reported to melt irregularly, particularly with high-temperature cautery.7
Because the IOLs and surgical instrumentation may vary among different countries, it is crucial to test their suitability before surgery. It is important to note that no IOLs have been approved by the US Food and Drug Administration for intrascleral haptic fixation, and the use of any IOL for this purpose is therefore considered off-label.
In terms of IOL power calculations, the size of the operative eye’s corneal white-to-white diameter is taken into account. For instance, in eyes with a longer axial length, which are typically eyes with a larger corneal white-to-white diameter, the optic will usually sit somewhat more anteriorly, so we typically select a sulcus power. On the other hand, in eyes with a shorter axial length, which are typically eyes with a smaller corneal white-to-white diameter, the optic will usually sit somewhat more posteriorly. In these cases, we typically select an in-the-bag power. For eyes with average axial length and average corneal white-to-white diameter, we usually select an in-the-bag power. Even if the IOL sits slightly more anteriorly, this would produce a slightly myopic result, which is generally preferable to a hyperopic outcome.
Regarding the required needles, thin-walled 30-gauge needles (inner diameter: 0.20 mm) provide the most secure tunnel for the haptics of 3-piece IOLs (diameter: 0.14 to 0.17 mm). The lumen of a standard 30-gauge needle (inner diameter: 0.14 mm) is too narrow to easily dock the haptics of 3-piece IOLs. Some surgeons instead use a standard 27-gauge needle because its lumen (inner diameter: 0.21 mm) is adequately sized for haptic docking. However, the outer diameter (0.41 mm) is significantly wider than the haptic, which may increase the likelihood of postoperative hypotony and requires a much larger flange to prevent IOL slippage. For comparison, the outer diameter of a 30-gauge needle is 0.31 mm.
A peripheral iridotomy should be performed in patients undergoing the Yamane intrascleral haptic fixation technique, particularly in high-axial myopes or in eyes with a larger corneal diameter because the optic may sit more anteriorly in closer proximity to the iris. Iris capture by the IOL has been reported in 8% of cases, more commonly in younger patients and with smaller optic diameters.1 IOL tilt may also contribute to pupil capture. The peripheral iridotomy helps prevent pupil capture and reverse pupillary block. It can be performed either with the vitrector or with micrograsping forceps and microscissors.
In addition, anterior vitrectomy should also be completed before flanged haptic fixation to remove the vitreous skirt neighboring the area of IOL placement and to minimize vitreous traction. This can be achieved by the anterior segment surgeon or in conjunction with a vitreoretinal surgeon, depending on the training and comfort level of the former. Other determining factors might include credentialing and surgical privileges at the surgery center, and whether a posterior vitrectomy is needed (eg, when an existing IOL has dislocated into the vitreous). If operating alongside a vitreoretinal surgeon is not an option, learning to perform a pars plana anterior vitrectomy may be necessary.
- 0.12-mm forceps
- 1.0-mm paracentesis blade
- Keratome blade
- Dispersive ophthalmic viscosurgical device
- Corneal suture (10-0 nylon)
- Fine-tip marking pen
- Anterior chamber maintainer or posterior infusion cannula
- Anterior or posterior vitrector
- Thin-walled 30-gauge needle (2)
- 3-piece IOL
- IOL injector and cartridge
- 23-gauge intraocular micrograsping forceps (1 or 2)
- Intraocular IOL-cutting microscissors
- Needle driver
- Tying forceps
- Vannas scissors
- Low-temperature cautery
For anesthesia, a retro- or peribulbar block is recommended. Topical or intracameral anesthesia alone is insufficient.
Pearl: Before starting, measure the corneal diameter horizontally and vertically. This will help to determine whether to implant the haptics horizontally, vertically, or obliquely. For example, if the horizontal corneal diameter is greater than 12.0 mm, consider implanting the haptics vertically or obliquely instead to minimize stretch on the haptics, which can subsequently lead to lens tilt. If this is not feasible, another alternative would be to make the scleral passes closer to the limbus than normally planned.
Pearl: The anterior ciliary arteries and long ciliary nerves typically course at 3:00 and 9:00, with some anatomical variability. Although there is no consensus yet on the best location for the scleral needle passes, placing the haptics somewhat obliquely may be advantageous in order to avoid these arteries and nerves. Therefore, we typically place the haptics at 2:30 and 8:30, or 3:30 and 9:30, which is ergonomically better as well.
- Two marks are first placed at the limbus 180 degrees apart. A radial toric axis marker or other similar instrument is used to verify that the marks are exactly 180 degrees apart and centered on the pupil. In the case of a decentered pupil, these marks can be centered on the intended position of the IOL optic (Figure 46-1).
Pearl: If 3-port pars plana vitrectomy is performed, sometimes the valved cannula ports can obstruct some of the maneuvers needed for intrascleral haptic fixation. If this is the case, once the vitrectomy is completed, 1 or 2 of these ports can be removed, leaving just the posterior infusion cannula in place. However, leaving at least one additional port in place until later in the surgery can be advantageous, such as if an IOL inadvertently migrates posteriorly during the intrascleral haptic fixation steps.
- Using calipers, ink marks are placed 2 mm posterior to the limbus on either side. It is critical that these marks are exactly 180 degrees apart and centered on the pupil or on the intended position of the IOL optic (Figure 46-2).
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