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Posterior chamber phakic lens requires strong knowledge of possible complications
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Posterior chamber phakic IOLs have become popular for the treatment of myopia. The Visian implantable Collamer lens, or ICL, from STAAR Surgical, is one of the lenses approved by the U.S. Food and Drug Administration for the treatment of myopia between 3 D and 20 D. It is placed behind the iris and in front of the crystalline lens. Obvious advantages include better quality and clarity of vision, predictable outcomes, good mesopic vision, quick recovery and reversibility, absence of dry eyes, UV protection, correction of higher refractive errors and use in thinner corneas. However, just as with any other procedure, complications may occur, and the surgeon needs to be familiar with prevention, diagnosis and management.
Proper insertion
Improper loading of the ICL into the cartridge can lead to difficult implantation. It is important to avoid air bubbles in the cartridge because they interfere with visualization (Figure 1). The marks to identify the side are the square etchings on the corners of the ICL haptics. They should be visible on the leading right haptic and the trailing left haptic (Figure 2). The central diamond etching or hole denotes the axis of cylinder.
Figure 1. Posterior chamber phakic Visian ICL injected inside the eye.
Images: Agarwal A
Figure 2. Posterior Slow injection of the Visian ICL.
The lens is loaded convex side up. It is important not to twist the ICL while pulling it into the cartridge. If the axis etchings remain in line and aligned with the cartridge lock, simple injection avoids a flipped or inverted ICL. In case axis etchings are in line but not aligned with the cartridge lock, the injector is twisted so as to have the axis etchings face upward. If the ICL is twisted within the cartridge, it is important to ensure that the leading axis etching faces upward before injecting.
Once the leading haptic has unfolded in the anterior chamber, the injector is twisted to now face the trailing axis etching upward before injecting further. Keeping a rod on top of the ICL while unfolding prevents unintentional twisting of the ICL. Slow injection and waiting to have the leading haptics unfolded before further injecting is crucial. Once completely in the anterior chamber, the haptics are gently flexed under the iris (Figure 3). Intraocular Miochol (Bausch + Lomb) is injected to constrict the pupil, and viscoelastic is removed. A peripheral iridectomy is not required with the newer CentraFLOW model (Figure 4).
Figure 3. Haptics of the Visian ICL tucked under the iris.
Figure 4. New CentraFLOW model, which has a hole in the center so one does not need an iridectomy.
Inverted lens
While these maneuvers contribute to uneventful implantation, what does one do if faced with an inverted ICL? An inverted ICL may be diagnosed clinically or on anterior segment optical coherence tomography. The ICL edge markings may be seen as flipped. An inverted ICL, if left alone, can lead to the development of cataract, necessitating explantation (Figure 5).
In experienced hands, it is possible to reinvert a flipped ICL. The ICL is rotated to make it lie horizontal, and the edge is lifted up with an injection of viscoelastic. It is then folded on itself so as to bring the convex side superiorly. If this maneuver does not reinvert it, the ICL may be rotated to bring the fold close to the incision. Viscoelastic injected into the fold while pushing the lower half outward reinverts the ICL.
Figure 5. Posterior chamber phakic IOL with cataract.
A flipped ICL may also give rise to postoperative inflammation and must be corrected. The technique of viscocannula-assisted reinversion of the ICL should be performed carefully while making sure at all times to avoid contact with the endothelium or the lens capsule. An inflamed iris and a small pupil may require iris hooks to be used. In case difficulty is experienced in viscocannula-assisted reinversion, the ICL may be explanted by pulling it out. It is then reimplanted carefully using the precautions described earlier. Care should be taken not to damage any intraocular structures during explantation. The incision need not necessarily be enlarged for explantation of an ICL, although if required, it may be enlarged slightly. In case of cataract formation, ICL explantation is followed by cataract extraction with IOL implantation.
Other points
An improperly loaded ICL may get stuck in the cartridge and not get injected into the anterior chamber. Forceful pushing may lead to tearing of the ICL and inability to implant it. Having a back-up lens may be a good option for beginning surgeons. Implanting the damaged ICL should be avoided. Toric ICLs are now more commonly being used for the correction of myopic astigmatism.
Correct positioning of the ICL is vital for a happy patient. Markings should be made with the patient in the upright position to avoid cyclotorsion. Once the ICL is injected, it is rotated to have the axis etchings aligned with the axis marked on the cornea. It is helpful to have the ICL placement sheet held upside down to align it correctly to the surgeon’s perspective of the eye being operated on. A rotated ICL, if significant enough postoperatively to affect vision, needs to be rotated again into the correct axis.
Conclusion
To conclude, the Visian ICL is a good option not only for the treatment of moderate to high myopia, but also in other conditions such as stabilized keratoconus. It is important for the operating surgeon to be aware of different complications and various modalities of management to obtain happy outcomes.