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PUBLICATION EXCLUSIVE: Managing excessive residual astigmatism after toric IOL implantation
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Even though 90% of our toric IOL cases should be within 0.5 D of residual astigmatism, there will be cases in which the outcome is intolerable for the patient and something must be done. The following discussion explains the proper management.
The first step is to reassure the patient that an adjustment can easily be made and to make sure that the refraction is stable. Toric IOLs rarely rotate after implantation, but the wound is not stable until at least 3 weeks after surgery with a 2.5-mm temporal incision and will fade another 0.25 D against-the-rule (ATR) between 3 weeks and 6 months. If the preoperative astigmatism was not exactly at 90° or 180°, then the fade may also affect the axis of the residual astigmatism. A stable refraction is the final answer.
Once the refraction is stable, the exact meridian of the toric IOL must be measured. This is most commonly done with the biomicroscope (slit lamp) using a reticule with meridians labeled from 0° to 180°. In addition to refraction and IOL orientation, you must also have postop keratometry, spherical equivalent power and toricity of the IOL and axial length to allow the calculation of the ideal alignment. There are two methods for the calculation: 1) postoperative keratometry and refraction and 2) observed IOL meridian and postoperative refraction — the latter being more accurate because postop keratometry readings often have an irregular component, reducing the accuracy.
• Click here to read the full publication exclusive, Clinical Optics 101, published in Ocular Surgery News U.S. Edition, November 10, 2016.