EyeWorld Asia-Pacific March 2018 Issue

IOL exchange for the young eye surgeon by Liz Hillma EyeWorld Staff Writer Tips and tricks for determining when and how to perform IOL exchange M issed target, dys- photopsia, malpo- sitioning, patient dissatisfaction: There is a myriad of reasons for an IOL exchange. In these cases, the surgeon needs to give the patient hope for a better outcome while also setting realistic expectations, said Nicole Fram, MD , clinical instructor of ophthalmology, David Geffen School of Medicine, Jules Stein Eye Institute, University of California, Los Angeles. According to one study that looked at multifocal IOL exchang- es in 35 eyes, 60% had blurred vi- sion as the surgical indication for exchange, 57% experienced photic phenomena, 9% had photophobia, 3% had a loss of contrast sensitiv- ity, and 29% had multiple com- plaints. 1 Zaina Al-Mohtaseb, MD , as- sistant professor, Baylor College of Medicine, Houston, said it’s impor- tant to explain to IOL exchange patients that there’s a higher risk for complications compared to their initial cataract surgery and that they might require further surgeries in the future. Exchange assessment Dr. Fram said it’s important for the physician to distinguish among issues arising from corneal pathol- ogy, neuropathy, or retinopathy. “The first steps … include a careful refraction, ocular surface and slit lamp evaluation, and dilated fun- dus exam. Ancillary testing, such as corneal topography, endothelial cell counts, macular SD-OCT, and retinal acuity meter, are critical to planning and diagnosis of comor- bid conditions,” Dr. Fram said. While a missed refractive tar- get may be addressed with PRK or LASIK enhancement, if the patient already had multiple laser treat- ments or severe dry eye, an IOL exchange may be preferred, Dr. Fram said. Dr. Al-Mohtaseb calculates a new refractive power by measuring topography and biometry and con- siders the remnant refractive error from the original implanted lens. “We looked at the refractive outcomes of our multifocal IOL exchange and noted that by con- sidering the IOL calculations and refractive outcomes of the original cataract surgery when choosing the second IOL, the mean numeri- cal and absolute refractive pre- diction errors were significantly lower,” Dr. Al-Mohtaseb said. Dr. Fram also tries to get some of the original calculations and baseline information from refer- ring doctors, in addition to run- ning her own biometry, corneal topography, and refraction. Using the refractive vergence formula may be inconvenient for some sur- geons. One can calculate the new IOL biometry in a pseudophakic setting or use the Barrett Rx for- mula, which requires the patient’s new and old biometry. For bag-to- bag exchange, one can use a short- cut by using the refractive error spherical equivalent and multiply- ing it by 1.2 for a myopic error and 1.5 for a hyperopic error to obtain the new IOL power. Additionally, intraoperative aberrometry can be very useful when the patient is aphakic or when there is a clean bag-to-bag exchange of PCIOL. Patients with positive or nega- tive dysphotopsias require a “more complex discussion,” Dr. Fram said. A negative dysphotopsia can be improved by performing reverse optic capture, elevating the optic above the anterior capsule, while positive dysphotopsias are often improved by changing the IOL de- sign from a square edge to round or switching from an acrylic to a silicone or collamer lens. Unfor- tunately, there are no truly round IOLs on the market and changing the material is the best approach at this time. Both Dr. Fram and Dr. Al- Mohtaseb cautioned about IOL exchange with an open posterior capsule. Dr. Al-Mohtaseb said if the posterior capsule is open, an- terior vitrectomy might be needed and a part of the lens should al- ways be grasped or stabilized with a pars plana safety basket suture or “Masket Basket” to avoid dropping it during IOL manipulation. Dr. Fram said if there is no capsule support or basket suture, she’ll leave the bisected optic connected just until the end to avoid losing it in these cases. How to manage the exchange Incision location should be con- sidered when approaching IOL exchange, Dr. Fram said. For bag- to-bag IOL exchange, a temporal clear corneal incision more than 3 months postop may be difficult to open or too anterior, thus favoring a superior limbal or scleral tunnel. From there, Dr. Fram said sev- eral paracenteses should be made to provide 360 degrees of access to the IOL. Elevate the anterior capsule with a dispersive ophthal- mic viscoelastic device (OVD) on a cannula. Once you see the OVD EWAP CATARACT/IOL March 2018 35 continued on page 36