In this article, surgeons explain how they get the most from the toric IOL, and what they do in cases in which the lens isn't enough. Implanting the lens as close to the astigmatic axis is key, however, and can sometimes be a challenge. Dr. Kershner notes that, if the surgeon implants the lens and inadvertently rotates it so that it's more than 15 degrees off the axis of astigmatism, it can actually worsen the cylinder. To help implant it on the correct axis, the preop evaluation is critical. If it's the latter, you'll remove it when you extract the crystalline lens.
Corneal topography is also important for locating the proper axis.
Dr. Kershner prints out the patient's topographic map and uses it during surgery to dial in the correct meridian on an aiming reticule in his operating microscope. This obviates the need to hold another instrument to indicate the meridian. To avoid the troublesome rotation of the lens during implantation, Dr. Kershner prefers to slide the lens into an incision on the axis of astigmatism. You don't have to do it temporally and then rotate the lens in the bag. One of Tarpon Springs, Fla., surgeon James Gills' treatments for large amounts of astigmatism is to piggyback toric lenses.