Eyeworld

I CHALLENGING CATARACT CASES N FOCUS 68 | EYEWORLD | SEPTEMBER 2019 Lastly, the Barrett Rx formula calculator assists with calculating outcomes for IOL exchange and piggyback IOLs based on refraction after cataract surgery. Preoperative and postopera- tive biometry is necessary for proper entry and completed results." "Sometimes we have to make an educated guess based on the status of the patient's fellow eye," Dr. Garg said. "If, however, the currently implanted IOL power is known and a proper refraction can be done, one can estimate the new IOL power. There are also online calcula- tors that can help physicians estimate the power needed." "I usually have the patient back monthly for several months to ensure a stable refraction," Dr. Schockman said. "Once the refraction with the current IOL is known, the 3:2 rule can be used to determine what new IOL power is needed. "Refractive predictability when scleral fixating an IOL after removing a dislocated IOL is less reliable since the effective lens position is so variable," Dr. Schockman continued. "I typi- cally choose an IOL power using the traditional methods or base it off a patient's prior IOL power. In such cases, it is important to discuss with the patient that residual refractive error is likely." vision is affected or if the IOL looks like it is about to fall posteriorly. "A fallen IOL risks reti- nal damage, inflammation, and long-term vision loss," she said. While it is impossible to predict, a slit lamp exam can provide a good sense of the possibility of it occurring. "I find it helpful to have the patient lay their head back to see how the IOL will behave once they are supine in the operating room. During this maneuver, some IOLs rotate posteriorly enough that I am able to properly plan for intraoperative help from my retinal colleagues." Vitreous in the anterior chamber should also be noted. Dr. Garg highlighted the need for the sur- geon to be prepared and to discuss the situa- tion with the patient in these cases. "When to exchange an IOL requires a thorough discus- sion with the patient about the risks, benefits, alternatives, and complications," he said. Recalculating powers Calculating IOL powers is particularly challeng- ing during IOL exchange. Patients should be counseled that the ability to hit the refractive targets is limited with secondary IOL place- ment. "IOL exchange power determination can be challenging and all patients are consented to understand that we cannot reliably predict the exact refractive target," Dr. Fram said. In her experience, the Holladay 1 formula helps obtain the best results. "Additionally, one should attempt to understand where the optic will sit in the eye. If it is sulcus placement with some capsule support, then the surgeon should adjust the IOL calculation and back off the power depending on the power of the IOL. If the fixation technique is optic capture, the IOL calculation should be adjusted for in-the-bag placement. The scleral fixation techniques are typically 2.5–3 mm posterior to the limbus depending on the white-to-white and an in-the- bag calculation is appropriate. That being said, having a record of the previous IOL implanted and a current refraction is an excellent starting point. One can then deduce the new power by adjusting the A-constants. In cases of aphakia or bag-to-bag exchange I find that intraopera- tive aberrometry is helpful to verify lens power. continued from page 66 Reference 1. Siegel MJ, Condon GP. Single suture iris-to-capsulorhexis fixation for in-the-bag intraocular lens subluxation. J Cataract Re- fractive Surg. 2015;41:2347–52. Relevant financial interests Fram: None Garg: None Hoffman: None Khandelwal: Carl Zeiss Meditec Schockman: None Subluxated IOL Source: Richard Hoffman, MD Contact information Fram: DrFram@avceye.com Garg: gargs@uci.edu Hoffman: rshoffman@finemd.com Khandelwal: SKhandel@bcm.edu Schockman: sschockman@cvphealth.com

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