EyeWorld Asia-Pacific September 2015 Issue

September 2015 13 EWAP FEATURE astigmatism alone, she said. Currently, she finds that the Cassini (i-Optics, The Hague, the Netherlands) is doing a great job helping to overcome this by also taking posterior astigmatism into account. Still, the total corneal astigmatism measurement is not quite as precise as it could be. “We have a pretty good understanding, but the technology is not 100% yet,” Dr. Yeu said. In addition, effective lens position plays a role in toricity correction 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, practitioners 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 surprises, 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 topography and do a slit lamp examination looking at the entire cornea to make sure that it is healthy. “Utilizing the Cassini as a diagnostic tool with everything else has certainly helped minimize and reduce my surprise because it gives me a better idea of what the true refractive 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 neutralize 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 importance of taking such cyclotorsion into account regardless of the system being used. He recommended marking patients’ eyes while they are sitting. He also advised practitioners to consider intraoperative aberrometry 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 refraction on the table,” he said. “In case you caused a new vector of astigmatism from your incisions, this will take that into account.” Handling errors Dr. Yeu finds that there are three groups of toric postoperative surprise patients with which to contend. The first includes those with obvious malrotation of the toric lens. “In that situation, it doesn’t hurt to look at what astigmatismfix.com says to see if rotating it into axis or into a different axis will help minimize their astigmatism error,” Dr. Yeu said. The second group is those who have mixed astigmatism, with no error in spherical equivalent. “If their spherical equivalent is zero, you know that if you fix the astigmatism part, they’re going to be very happy with their vision,” Dr. Yeu said. If this astigmatism is less than 1 D, Dr. Yeu will place a limbal relaxing incision in the steep meridian. If there is undercorrection of astigmatism and an LRI is also present, she will try titrating and opening limbal relaxing incisions in the axis. However, if there is more than 1 D of astigmatism postoperatively, Dr. Yeu will consider laser vision correction or an IOL exchange depending on patient-specific characteristics and needs. For those in the third group, both their astigmatism and their spherical equivalent are off. In that group, it becomes a choice of IOL exchange versus laser vision correction. Deciding between these may come down to the patient’s ability to wait for laser vision treatment for 2–3 months, Dr. Yeu said. “I want to make sure that they’re off drops and that their ocular surface is healthy enough to provide an accurate refraction,” she explained. Dr. Serafano also won’t perform laser vision correction for residual astigmatism until about 3 months have gone by. “I want to make sure that they have stable refraction and that’s what they want done,” he said. Ultimately, it all comes down to the patient, he said. “I think the patient determines whether or not any secondary intervention is necessary,” Dr. Serafano said. “If a patient is accepting, even though you may have a mathematical error on your refraction, I think you’re done.” However, if the patient is unhappy, it is then a question of going through the options. “If you find out that rotation would help them, you can offer that,” Dr. Serafano said. “If the patient doesn’t want to go back to the operating room, you’re faced with either glasses or laser vision correction.” Dr. Serafano stressed the importance of understanding why that surprise occurred in order to prevent it from happening again. “I think whether or not you trace it back to an abnormal topography or some misalignment, in the end it’s important to know why,” he said. Going forward, he hopes that practitioners will do more educating on treatment of astigmatism. “I think that if we can better teach how to analyze and treat astigmatism, we’re going to find the use of toric lens implants will increase significantly,” Dr. Serafano concluded. EWAP Editors’ note: Dr. Serafano has financial interests with Alcon. Dr. Yeu has financial interests with Alcon and Abbott Medical Optics (Abbott Park, Ill.). Contact information Serafano : serafano@verizon.net Yeu : eyeulin@gmail.com