Eyeworld

50 | EYEWORLD | DECEMBER 2023 R EFRACTIVE References 1. de Castro A, et al. Tilt and decentration of intraocular lenses in vivo from Purkinje and Scheimpflug imaging. Validation study. J Cataract Refract Surg. 2007;33:418–429. 2. Rosales P, Marcos S. Phakome- try and lens tilt and decentration using a custom-developed Purkinje imaging apparatus: validation and measurements. J Opt Soc Am A Opt Image Sci Vis. 2006;23:509–520. 3. Marcos S, et al. Three-dimen- sional evaluation of accommo- dating intraocular lens shift and alignment in vivo. Ophthalmolo- gy. 2014;121:45–55. 4. Sun M, et al. Intraocular lens alignment from an en face optical coherence tomography image Purkinje-like method. Opt Eng. 2014;53:061704. 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 differ- ence 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 decentra- tion, 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 position- ing the capsulorhexis. A tool like the femto- second laser where you can be very precise or the ZEPTO IOL Positioning System (Centricity Vision), which makes a precise, round capsulor- hexis, may help, he said. Some patients may experience a major decentration, rather than just a minor issue. These major decentrations would likely come from a surgical complication, Dr. Ayres said, like a severe zonulopathy or posterior or anteri- or capsular tear. Patients may notice reduced vision, double images, or dysphotopsias due to reflections off the edge of the lens implant. "The problem we have is fixing that IOL or replacing it with a new lens using an alternative "I don't lose too much sleep over decen- tration 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 dis- continuous 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 pseudoexfolia- tion 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 zonu- lar 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 myo- pia, a history of trauma, or Marfan syndrome. "Specific lenses may exhibit designs that make them critical to align with the pupil cen- ter," 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' experi- ence, 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 continued from page 49 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

• Cover