22 EWAP MARCH 2024 REFRACTIVE way to a tilted suture-fixated lens that induces 4 or 5 D of astigmatism. When thinking about tilt and decentration with standard monofocal lenses, Dr. Ayres said this is something that can be seen but is not usually a major concern. With some of the more advanced technology lenses, the aspheric IOLs especially, if they begin to decenter, there may be a decrease in quality of vision. If there’s a capsule complication and you can’t get the lens in perfectly centered or if there’s asymmetric phimosis or scarring of the capsule, it can cause a decrease in visual quality. There’s less of an issue optically if you’re using a non-aspheric or a zero asphericity lens, Dr. Ayres said. If there are small amounts of decentration due to patient healing, it’s not going to impact quality of vision as much. “I don’t lose too much sleep over decentration of standard IOLs because it’s not a major problem,” he said. There are a variety of implant options now available. Some are zero asphericity and some transition from negative to zero asphericity depending on where you are in the lens. Risk factors for decentration include a discontinuous capsulorhexis, a small capsulorhexis, a decentered capsulorhexis, if you can’t get a good overlap of the anterior capsulorhexis with the IOL, and patients who are more prone to capsular phimosis like those with pseudoexfoliation or high myopia. In uneventful cataract surgery, Dr. Marcos finds that standard IOL platforms preserve, to a large extent, the tilt and decentration of the natural bag, though she noted that this does not include complications like dislocation and zonular weakness. “We also found a larger amount of tilt in eyes implanted with lenses with hinged haptics,” she said, adding that these lenses did not preserve the orientation of the preoperative capsular bag. Dr. Marcos does not see a huge concern for these issues in standard cataract surgery, but she said it’s important for surgeons to anticipate when they might have a complicated surgery. This includes patients with a history that makes them likely to have zonular weakness, like severe pseudoexfoliation, high amounts of myopia, a history of trauma, or Marfan syndrome. “Specific lenses may exhibit designs that make them critical to align with the pupil center,” Dr. Marcos said. “To my knowledge, most designs have some tolerance to the amount of tilt and decentration in normal cases (<0.5 mm, <5 degrees), but in some cases, haptic designs could be envisioned to ensure centration.” Extreme decentration, in Dr. Ayres’ experience, is usually due to capsular phimosis. “The times I’m dealing with this are when there is capsular phimosis shortly after cataract surgery. I’m very quick to do a YAG laser and relax the anterior capsule by doing anterior capsular polish, which is basically a YAG capsulotomy to the anterior capsule to break the phimotic or scarring ring.” This lets the implant settle in a better position, he said. “It’s not that common with a monofocal lens that I’m going back to the operating room to recenter it,” Dr. Ayres said. “However, in a toric IOL or multifocal IOL that’s decentering, and we think that decentration is causing a decline in quality of vision, that’s different. There we will go back to the operating room and reopen the capsule and try to rotate the lens, if necessary, or reposition the lens so that it’s better centered because that little bit of decentration, especially with the diffractive multifocal, makes a difference and you can see a rapid decline in quality of vision.” Toric IOL rotation is going to happen in some patients, Dr. Ayres said, whether it’s due to retained ophthalmic viscosurgical device, the patient rubbed their eye, or the patient has a larger eye than average or is a high myope. If you know someone is at risk for decentration, you have to be more proactive, Dr. Ayres said. For example, if you’re operating in a high myope, some physicians would place a capsular tension ring (CTR) to prevent decentration or to have equatorial forces out to reduce scarring and phimosis, and that may help with the IOL staying centered. It’s also important to make sure you are appropriately sizing and positioning the capsulorhexis. A tool like the femtosecond laser where you can be very precise or the Decentration of a multifocal toric IOL due to asymmetrical healing of the capsular bag. In this case, the patient experienced severe degradation of vision, and the IOL had to be removed and replaced. Source: Brandon Ayres, MD
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