![]() ![]() I regularly see patients with unrecognized Salzmann nodules. The slit-lamp examination showed nasal Salzmann nodules in her left eye. Her BCVA was 20/300 with a refraction of -4.00 +5.50 × 95º, and she had a 3+ nuclear cataract. Her habitual glasses prescription in her left eye was -2.75 D sphere, but she reported progressive worsening of her vision and was referred for cataract surgery. ![]() The patient had undergone cataract surgery with a multifocal IOL in her right eye 10 years earlier. Using a digital marking system has improved the accuracy of my toric IOL placement and reduced the time I spend on aberrometry adjustments, but with careful marking and technique, surgeons can achieve fantastic results with manual marking alone. I utilize intraoperative aberrometry to fine-tune both the IOL’s spherical power and the axis, but I rarely change the cylindrical power unless I am using aberrometry to help decide between two powers. It may be accessed through a link in the “Online Tools” area of the American Society of Cataract and Refractive Surgery’s website ( or the Asia-Pacific Association of Cataract & Refractive Surgeons’ website ( I use the HofferQ, Holladay 1, SRK/T, Holladay 2, Haigis, and Barrett formulas in combination to choose the spherical power and then calculate the cylindrical power separately. 8-10 Another option now available is the Barrett Toric Formula. I do not use a manufacturer’s online calculator, but these tools have improved and are excellent because most take IOL power and posterior corneal astigmatism into account. Similarly, the ratio between the toric power at the IOL plane and the corneal plane depends on the IOL’s position. 4-7 That means that a +28.00 D SA6AT4 AcrySof IQ Toric IOL (Alcon) will correct more astigmatism than a +8.00 D SA6AT4 lens. 1-3 Furthermore, IOLs with high spherical powers have a greater toric effect, even if their toricity is identical. As reported by Koch et al, the posterior cornea causes against-the-rule cylinder that is not captured well by most devices. It is important to keep the axis of the correction in mind, undercorrecting with-the-rule cylinder and overcorrecting against-the-rule cylinder. ![]() Simply picking the toric power based on this number, however, can lead to unsatisfactory results. Fortunately, most individuals fit this description. The ideal candidate for toric correction has regular astigmatism, with agreement among the three K measurements. Patients are asked to stop wearing soft contact lenses 2 weeks prior to their visit and rigid gas permeable lenses 3 weeks before their appointment-longer if necessary for their corneal topography to become regular. It is critical that the patient’s head be level, even if it is habitually tilted, and the studies should be performed on a pristine cornea. The iTrace gives a best-fit keratometry (K) reading cumulatively through the central 3 mm that I use instead of its simulated K readings. All patients in our office receive three preoperative astigmatism measurements: auto keratometer, IOLMaster 700 (Carl Zeiss Meditec), and iTrace (Tracey Technologies). ![]() By definition, calculating for a toric IOL requires selecting a spherical power, cylindrical power, and axis. ![]()
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