Bonnie An Henderson, MD, provides tips for marking the eye to guide toric IOL orientation.
Boston—Toric IOL implantation provides a reliably effective method for reducing existing astigmatism in patients undergoing cataract surgery, but careful marking of the eye to guide accurate axis alignment of the IOL is essential for achieving good outcomes, said Bonnie An Henderson, MD.
“Astigmatism correction is becoming a more important component of cataract surgery, as surgeons aim to meet the high expectations of today’s patients,” said Dr. Henderson, clinical professor of ophthalmology, Tufts University School of Medicine, Boston. “However, carefully marking to identify the steep axis is needed for proper IOL alignment and achieving the desired outcome, because for every 1° that a toric IOL is off-axis, its effect for reducing astigmatism is decreased by 3.3%.”
Providing tips for marking the eye when implanting a toric IOL, Dr. Henderson said the first issue to consider is the possibility of cyclorotation when patients move from an upright position to supine under the surgical microscope. Therefore, placement of the preoperative reference markings that will guide intraoperative marking of the axis should be made with patients in a sitting position.
“Researchers evaluating cyclorotation of the eye in LASIK patients reported an average positional change of 4.1° and rotation of more than 10° in 8% of eyes,” Dr. Henderson said. “The resulting misalignment in the latter situation would reduce the astigmatic correction provided by the toric IOL by one-third.”
Making the mark
To make the mark, the surgeon first should instruct the patient to look straight ahead, focusing on a fixed point in the distance past the surgeon’s shoulder. While resting one’s hand on the patient’s cheek to enhance manual control of the marker, marks should ideally be placed on the limbus at the 3, 6, and 9 o’clock meridians of the cornea or at least at 3 and 9 o’clock. For increased precision, the reference marks should be done on a dry eye using a commercially available premarker inked on an ink pad and by first placing the premarker below the eye and then moving it up and straight toward the eye.
“Check that the patient’s head is not tilted left or right,” Dr. Henderson said. “Make sure the cornea is dry before placing the mark. If the cornea is too wet, use a Weck-cel sponge to dry the area of the eye to be marked.
“Ink the marker in a vertical direction to get more ink, but be careful not to use too much ink,” she said. “A large mark from ink that smears or bleeds on the surface will cover a range of degrees and compromise the precision of the IOL alignment.”
Intraoperatively, any marking that has faded should be enhanced by hand. Then, using the preoperatively placed reference marks, the steep axis should be marked with an axis marker using a “rock-and-roll” technique rather than by “stamping” the eye.
“I recommend operating on the steep meridian, and marking the steep axis will identify the incisional axis and axis for IOL orientation,” Dr. Henderson said.
However, she added that online toric IOL calculators will calculate the correct power and alignment of the toric IOL based on the input for incision location.
So that the markings are made with the eye in its most natural state, the intraoperative marking should be done prior to administering any blocks or making any incisions. However, the accuracy of the marking should be checked a second time prior to implantation of the IOL.
“Measure twice and cut once,” Dr. Henderson said. “Then, as a final check, make sure the implanted IOL is on axis prior to removing the drapes.”
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