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    Learn how curiosity propels astigmatism innovations


    What he found was that the axis varies widely, but the centroid value does not.

    “It doesn’t matter where you put the incision—temporal axis or steep axis. The centroid value is pretty much 0.1 or less,” he said. “Even with smaller incision sizes, it’s irrelevant where you place the incision, the centroid value remains around 0.1. I confirmed this with a series of more than 1,000 eyes.”

    Which is superior: LASIK or contact lenses?

    In a personal series of 40 eyes with smaller incisions of 2.2 to 2.4 mm, centroid values do not change.

    His advice: “Don’t operate on the steep axis to reduce astigmatism, as it’s too variable. Preferably go on the temporal axis and go to 2.4-mm incision and use a centroid value of about 0.1, regardless of the prediction.

    Despite accurate keratometry, he said, implantation is not always predictable.

    Toric IOL more challenging choice

    “Choosing the correct toric IOL for patients is more challenging than choosing a spherical IOL power,” he said.

    Toric IOL alignment is a critical component to its success, and Robert H. Osher, MD, “first convinced me freestyle marking was not enough,” Prof. Barrett said.

    Instead, Dr. Osher’s concept of “iris fingerprinting” provides more reliable results, and it’s now being incorporated into image-guided systems.

    Sponsored: 5 reasons toric IOLs manage astigmatism most effectively

    Prof. Barrett has developed the “ToriCam” app to aid in axis marking, where “all you need is the app and a felt-tip marking pen,” he said.

    First, dry the limbus and mark where the 180° axis is, he said. “It doesn’t matter if you’re not spot on. Use the app to align with the mark and you’ll have the previous five images the app took—allowing you to see where the true axis is.”

    In an analysis of 40 eyes comparing slit lamp and freehand alone to both slit lamp and freehand with the ToriCam showed the combination improved accuracy by 50% in the slit lamp combination and by 68% in the freehand combination.

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