Toric IOLs present a significant advance in the correction of astigmatism and improvement of uncorrected visual acuity. However, the smallest error or misalignment of the lens could cause refractive surprises, affecting positive outcomes and in some cases actually worsening the patient’s vision.
As a surgeon, it can be frustrating to perform a beautiful procedure, knowing with certainty the correct axis was identified and the lens placement was spot on during surgery, only to discover a surprise after the procedure. Not uncommonly, a misaligned IOL is the culprit despite correct initial placement.
Possible causes of shifting IOLs
While rare, these misalignment occurrences could be caused by a number of dynamics. Some obvious risk factors include asymmetric or large diameter capsular bags, longer axial lengths, or a too large or decentered capsulorrhexis. These may cause rotation of the lens because the reduced area of contact between the rhexis edge and the optic could lead to a subtle destabilization of the optic during postoperative healing. Anterior chamber shallowing could also cause the optic to lose contact with the posterior capsule. To avoid this particular circumstance, I altered my surgical technique slightly. At the conclusion of cataract surgery, after all my wounds are sealed and watertight, I re-enter the anterior chamber with a 30-gauge cannula and tap down the IOL one more time to promote contact with the optic and adhesion.
In my experience with the small series of patients in which rotation has occurred, those who are aligned with-the-rule or oblique seem to rotate more than the ones who are aligned against-the-rule. Additionally, excess viscoelastic behind the IOL could lead to potential issues with contact and the optic. Care should also be taken not to hyperinflate the eye. Hyperinflation, especially of a myopic eye, can lead to greater inflation of the bag and cause the lens to float and lose contact. If the eye is left hyperinflated, it is wise to ensure the optic is in contact with the capsule in order to mitigate any surprise.
A particularly notable cause is when certain patients, especially intraoperatively, have a tendency to squeeze or blink strongly. If this occurs, it could cause a watertight wound to lose its seal. That strong squeeze or blink reflex could induce a “burp” of the wound or a subtle egress of aqueous out of the eye. This instability, coupled with the strong squeeze, could lead to the IOL moving out of position.
Ocular sealant for advanced technology IOLs
To combat the possibility of the lens misaligning, I now utilize ReSure Sealant (Ocular Therapeutix), specifically in those patients who are more at risk not only in toric lenses, but also in multifocal lenses because having perfect centration is invaluable for multifocal IOL results. A pliant hydrogel, this sealant is composed of polyethylene glycol, trilysine, buffering salts and more than 89% water. The ocular surface must be completely dry in order for the sealant to properly adhere. Application is quick and efficient, taking only seconds to administer, and it polymerizes into a pliant, synthetic hydrogel in less than 30 seconds. The FD&C Blue No. 1 element of the gel aids accurate placement and dissipates within hours, leaving a clear sealant on the eye that naturally dissolves. Clear corneal incisions commonly leak, whether hydrated or closed with sutures, and this egress can lead to subtle rotations and refractive surprises. This sealant has been shown to efficiently seal wounds, preventing even a strong lid squeeze from causing egress of fluid, thereby aiding in the prevention of IOL placement shifts.
With so many possible factors that can lead to postoperative lens rotation out of a physician’s control, taking this small step to ensure a watertight wound seal is significantly beneficial in mitigating some of the risk. Even patients with a strong blink reflex can be assured the lens will remain sound. Because cost is a consideration, I particularly advocate the use of the sealant for all patients who are at a higher risk of displacing the lens, such as higher axial myopes or those I perceive perioperatively to have a stronger blink reflex.
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- Masket S, et al. J Cataract Refract Surg. 2014;doi:10.1016/j.jcrs.2014.03.034.
- Mifflin MD, et al. J Cataract Refract Surg. 2012;doi:10.1016/j.jcrs.2012.04.019.
- For more information:
- Elizabeth Yeu, MD, can be reached at Virginia Eye Consultants, Norfolk Office, Office & Surgery Center, 241 Corporate Blvd., Norfolk, VA 23502; email: email@example.com.
Disclosure: Yeu reports she is a consultant for Alcon Surgical, Abbott Medical Optics, Bausch + Lomb and Ocular Therapeutix.