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Unfolding of IOL key to glued intrascleral fixation
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Glued intrascleral fixation of a posterior chamber IOL is a technique aimed at restoring pseudophakia in patients with posterior capsular dehiscence. This technique has evolved from the usage of PMMA non-foldable IOLs to the application of modern three-piece foldable IOLs, extending all the advantages of a small-incision surgery.
The pattern of unfolding an IOL in the anterior chamber is the key to the outcome of the surgery. The surgeon should appreciate both the “lucky 7” sign, a term coined by Thomas Oetting, MD, or the “inverted C sign” and the “upright C sign” during the process of unfolding the IOL, which should be slow, gradual and done in a controlled manner to facilitate the grasping of the haptics.
Inverted C and upright C signs
The IOL is loaded, and the tip of the leading haptic is slightly protruded from the cartridge. The surgeon introduces the glued IOL forceps from the left sclerotomy site and catches the tip of the leading haptic in the eye. At this step, the leading haptic is in the form of a lucky 7 or inverted C (Figures 1 and 2). The IOL is slowly unfolded into the anterior chamber, and the cartridge is withdrawn at the end so that the trailing haptic lies at the corneal incision. The trailing haptic showcases an upright C sign (Figures 3 and 4). The presence of both these signs ensures that the IOL has unfolded in an appropriate manner. If these signs are not appreciated (Figure 5) or if they are in a reverse pattern, ie, upright C sign for the leading haptic and an inverted C sign for the trailing haptic, then it suggests that the IOL has unfolded in a reverse fashion. In such a scenario, the surgeon has two options:
Figure 1. Illustration showing the inverted C sign of the leading haptic.
Figure 2. Inverted C sign of the leading haptic.
Images: Agarwal A
Figure 3. Illustration showing the upright C sign of the trailing haptic.
Figure 4. Upright C sign of the trailing haptic.
Figure 5. Note the IOL not coming in the proper inverted C sign method.
Figure 6. Handshake technique to grasp the tip of the haptic.
1. The IOL can be flipped upside down in the eye, and then the surgery can be continued as planned.
2. The surgeon can externalize the haptics from both sclerotomy sites with the variation that the scleral pockets are made in the opposite direction as previously planned.
If an upright C sign is seen for the trailing haptic in the anterior chamber instead of at the corneal incision, it should be taken as a warning sign and the surgeon should concentrate on the externalization of the leading haptic. Slippage of the leading haptic at this juncture can lead to an IOL drop. After externalization of the leading haptic, the surgeon can maneuver the manipulation of the trailing haptic with the handshake technique wherein the IOL haptic is bimanually transferred from one glued IOL forceps to another under direct visualization in the pupillary plane until the tip of the haptic is grasped to facilitate easy externalization (Figure 6).
After both the haptics are externalized, the scleral pockets are created with a 26-gauge needle and the haptics are tucked in them. Vitrectomy is done at the sclerotomy site, infusion is stopped, and the flaps are sealed with fibrin glue.
IOL injectors
A user-friendly, predictable IOL injector system for three-piece IOLs is used in glued IOL surgery to achieve a fully controlled unfolding. A number of these injectors are available, making it possible for surgeons to deliver three-piece lenses in the desired manner.
1. Abbott Medical Optics: AMO currently offers advanced delivery systems for hydrophobic acrylic IOLs. The Sensar A40 is a three-piece acrylic, hydrophobic IOL with an optic diameter of 6 mm, an overall length of 13 mm with a modified C-loop configuration, and blue PMMA monofilament haptics. It can be delivered through an incision as small as 2.8 mm.
The Unfolder Emerald series is designed exclusively for use with the Sensar with OptiEdge hydrophobic acrylic IOL. The Unfolder Emerald series should be used in conjunction with the Emerald C small-incision cartridge.
The features include a conical tip that does not change wound architecture; a highly polished rod tip, designed to preserve the optic surface; an enhanced tip design that facilitates haptic release and control; and a wider thread design that requires fewer twists for efficient IOL advance.
It has a rotating mechanism that requires an assistant to continuously twist the injector while the IOL is being unfolded. The unfolding of the Sensar IOL is ideal for glued IOL surgery.
2. Alcon Laboratories: For IOL implantation, Alcon offers the Monarch II IOL delivery system. The Monarch II is compatible with AcrySof multi-piece IOLs. The proprietary cartridge design allows for smooth, sterile implantation of the IOL. The knob of the plunger is rotated for controlled delivery of the lens.
3. Bausch + Lomb: The Bausch + Lomb SofPort IOL has a uniform lens power from center to edge, and the SofPort AO lens is a more “forgiving” optic design that minimizes the deterioration of optical performance in the event of decentration. Bausch + Lomb also has the SoFlex IOL, a three-piece foldable IOL.
Features include three-piece silicone IOL with a 13-mm overall length, 6-mm optic and PMMA modified C-loop haptics; aberration-free aspheric optics that enhance contrast sensitivity, do not reduce depth of field and do not induce aberrations when decentered; easy-load inserter with one-handed planar delivery; and indications for placement in capsular bag and ciliary sulcus.
The Bausch + Lomb injector has an advantage with a plunger-injecting mechanism for the IOL unfolding. This gives better control to the surgeon during the surgery because he is not dependent on an assistant to twist the injector.
4. STAAR Surgical: Collamer and silicone three-piece IOLs are available. A silicone IOL with 13.5-mm and 14-mm lengths for low dioptric powers is also available in the United States. These IOLs have polyamide haptics that can be tucked in the scleral pockets.
Most of the STAAR injectors are available in two variants: MSI-TM (twist) or MSI-PM (plunger). This inserter is used to deliver silicone three-piece lenses with a 6.3-mm optic. STAAR recently introduced a new lens delivery system called Epiphany, a dual-insertion technique to eliminate the need for multiple injectors. It is specially designed for use with Collamer three-piece aspheric IOLs.
Conclusion
Overall, for a glued IOL surgery, the correct and well-controlled unfolding of an IOL is essential because it can be unforgiving at times due to the absence of a posterior capsule. Simultaneous coordination of the hand movement of the surgeon and the correct unfolding of an IOL with the appreciation of a lucky 7 or an inverted C sign for the leading haptic and an upright C sign for the trailing haptic intraoperatively are key to the successful outcome of the surgery.