Eyeworld

EW FEATURE 72 Revisiting astigmatism • October 2018 "Of course, it all depends on how accurate your preop measurements are and how you are marking where to place your incisions." Dr. Green- wood said that if your marks are not accurate, the placement of the incisions may not be at the axis you initially intended. "This is especially important as the eye can cyclorotate when laying supine." Prior to placing the IOL, Dr. Greenwood uses intraoperative aberrometry to help select the IOL power and measure the total corneal astigmatism. "If I did AKs and there is still some residual astigmatism, I can open them to get a greater ef- fect," he said. "If I chose a toric IOL, I will use the measurements to guide the toric power selection." Dr. Baartman said that he likes the accuracy of the femtosecond laser for placing astigmatic inci- sions at precisely the right position, depth, length, and centration. "On the femtosecond platform, OCT im- aging allows me to be very specific in my intended depth of 90%, and I can feel confident in its safety," he said. "I also appreciate the ability to open or not open the incisions, and I often make that decision with the use of intraoperative aberrometry." Advantages of toric IOLs Dr. Baartman thinks toric lenses have the advantage of being able to treat larger amounts of refractive astigmatism without making large incisions on the cornea. "This can come into play when treating pa- tients with ocular surface disease or a history of keratorefractive surgery, when incisional refractive surgery may not be best for the patient," he said. "Particularly in those patients with larger amounts of cylinder, you have the ability to rotate a toric lens or employ an excimer laser to touch up residual astigmatism." Ultimate- ly, Dr. Baartman said that this helps preserve more of the corneal tissue and natural strength compared to strictly using an incision or kera- toablative refractive surgery. The biggest advantage is that they can correct higher amounts (greater than 1.5 D) of astigmatism compared to AKs or LRIs, Dr. Green- wood said. "I also like torics in the lower astigmatism range (1.0–1.5 D) because we are less dependent on patient healing and the response of the cornea to the incisions," he said. "The other great thing about toric IOLs is with the intraoperative aberrometry I can take a measure- ment after I have made my cataract incisions and get real time feedback from the aberrometry to show me the steep axis and exactly where to place the IOL." Physicians have learned that for each degree they are off axis, they lose 3% of the power of the toric, Dr. Greenwood said, adding that this may not be much on a lower powered toric, but in a high powered toric, that can be a big difference if off just a few degrees. EW Editors' note: Dr. Greenwood has financial interests with Alcon. Dr. Baartman, Dr. Miller, and Dr. Yeu have no financial interests related to their comments. Contact information Baartman: brandon.baartman@vancethompsonvision. com Greenwood: michael.greenwood@vancethompsonvision. com Miller: kmiller@ucla.edu Yeu: eyeulin@gmail.com "I always go for femto AKs for a primary case," Dr. Yeu said, adding that she uses the femtosecond laser at the time of surgery as it helps create a standardized capsulotomy and provides a more predictable refractive outcome. Accuracy of LRIs and femto AKs Dr. Greenwood said that he finds femto AKs more accurate in that they are more precise. "Manual tech- niques are good, but we will never be as precise as the laser, whether it is AKs or capsulotomies," he said. Correcting continued from page 70 The posterior cornea on the Cassini LED topographer demonstrates a small amount of with-the-rule astigmatism, which ultimately leads to a total corneal astigmatism that is slightly more than 1 D. Source: Elizabeth Yeu, MD This 68-year-old female wants a higher quality of uncorrected distance vision with cataract surgery of the left eye. The LENSTAR and Placido disc topography show good alignment in the quantitative values, with about 1 D of anterior corneal astigmatism around 165 degrees.

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