Eyeworld

EW FEATURE 52 Toric IOLs June 2015 Dr. Yeu said that another huge source for such errors is the "un- known" factor. "There is more to astigmatism correction than what we see on the anterior corneal sur- face," she said. "So it's managing the total corneal astigmatism." This is still not as accurate as measurements of the anterior astig- matism alone, she said. Currently, she finds that the Cassini (i-Optics, The Hague, the Netherlands) is do- ing a great job helping to overcome this by also taking posterior astig- matism into account. Still, the total corneal astigmatism measurement is not quite as precise as it could be. "We have a pretty good understand- ing, but the technology is not 100% yet," Dr. Yeu said. In addition, effective lens posi- tion plays a role in toricity correc- tion and can also be an unknown, she said. For example, for patients who have eyes shorter than 23 mm or longer than 25.5 mm, practi- tioners have to be wary. "They're going to have different effective toricity corrections [than others] from that IOL," Dr. Yeu said. "We don't know how the effective lens position is going to change the effect of that IOL." Problems with the corneal surface can also play a role in toric surprise. "In general, the biggest issue that I see with patients who are being sent to me for toric surprise is a preoperative ocular surface issue," Dr. Yeu said. This includes patients who have dry eye that is not well managed, as well as those with undiagnosed and untreated anterior basement membrane dystrophy and Salzmann's nodular degeneration. These patients can have huge swings in their postoperative results because of undiagnosed corneal issues. To help avoid refractive surpris- es, Dr. Yeu advised practitioners to take good care of the ocular surface. "Babying that ocular surface is huge," she said. Physicians should get a good assessment with topogra- phy and do a slit lamp examination looking at the entire cornea to make sure that it is healthy. "Utilizing the Cassini as a diag- nostic tool with everything else has certainly helped minimize and re- duce my surprise because it gives me a better idea of what the true refrac- tive astigmatism is—not just what's showing on the anterior surface," Dr. Yeu said. Lastly, when dealing with extremely long or short eyes, she recommended using a "fudge factor" to help maximize the toric correction. "If they have a shorter eye, I'll bump down the toric power correction," she said. "If they have a long eye, I'll consider bumping up by one toric level." Dr. Serafano noted that the Verion (Alcon, Fort Worth, Texas) can also be used for better patient registration. He finds that working with the Verion helps to neutral- ize the cyclotorsion that can occur when the patient is first examined in the office in the sitting position compared to when they are lying down in the OR for the procedure. It does this by honing in on limbal vessels and iris features during the exam, which can then be taken directly to the laser in the operating room. "You can get registration at the end that then takes into account cyclotorsion and gives you the proper axis as a heads up display," he said. Dr. Serafano stressed the impor- tance of taking such cyclotorsion into account regardless of the sys- tem being used. He recommended marking patients' eyes while they are sitting. He also advised practitioners to consider intraoperative aberrom- etry with the ORA (Alcon) when determining toric IOL selection. "With the ORA you can now take an aphakic refraction and verify not only the spherical power but also the cylinder power," he said. This may change your toric IOL selection and also inform your decision on how much IOL rotation is needed, Dr. Serafano noted. "This has to tighten up your results because now you have taken into account your incision and you're doing a pseudophakic refrac- tion on the table," he said. "In case Blowing out the candles continued from page 50 Patient's right eye before treatment for dry eye disease Patient's right eye after dry eye disease treatment Source: Elizabeth Yeu, MD continued on page 54

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