Eyeworld

and should you go with a car with that extra overdrive gear? The point is, there are a lot of little differences that when put together can have a signif- icant impact on the outcome; this is so, too, with toric IOLs. The game has changed: It is no longer good enough to only correct sphere and cylinder; these days, we are also expected to correct higher order aberrations. This is why the Tecnis Toric IOL (Abbott Medical Optics, Abbott Park, Illinois) is an ideal choice of toric. In addition to spherical aberration correction, the Tecnis Toric also corrects chromatic aberration. This works in synergy with the IOL's high quality optic, which has a low refractive index to minimize dysphotopsias, is completely glistening-free, and provides full light transmission. Validating optical synergy A retrospective analysis of 927 cases of patients undergoing surgery from September 2011 to May 2016 was conducted to validate the effectiveness of the Tecnis Toric IOL in correcting astigmatism. A single surgeon conducted the operation using a single technique. Cases were followed up a minimum of 1 month. Before going into the details, one thing to remember is that when we measure ker- atometry, we are not measuring the curvature of the cornea. Instead we are measuring a reflection from the tear film; as such, it is imperative to conduct biometry on virgin tear film. In this study, patients had corneal astigmatism of 0.6 D or greater. The study included patients with astigmatism from A lmost half (40%) of patients who present with cataracts will benefit from astig- matism correction, particularly as patients these days tend to expect spectacle independence after cataract surgery. Toric IOLs may cost more upfront, but surgical options such as manual astigmatic keratoto- my carry the risk of inducing aberrations. In addition, toric IOLs provide more predictable and more stable refraction than manual incision surgery and ultimately may reduce dependence on spectacles and contact lenses over a patient's lifetime. 1,2 In the details There is quite a selection for surgeons to work through, so choosing a toric IOL is almost like asking which new car you should buy. When buying a new car, you might find yourself confronted with a barrage of tiny little details—this car might be 5% lighter, or 1.5 inches wider; one might have a design that offers a 5% reduction in drag, an engine that reduc- es emissions by 13%, with a selection of compression ratios ranging from 1:15.5 to 1:16.2; Daniel Black, MBBS, FRANZCO Which toric IOL should I use? Daniel Black, MBBS, FRANZCO, Sunshine Eye Clinic, Sunshine Coast, Queensland, Australia 2 Evolving technology and outcomes in cataract and refractive surgery Figure 1. Digital marking resulted in significantly less postop astigmatism than ink marking (p=0.02). Source: Daniel Black, MBBS, FRANZCO primary and secondary causes, including post-surgery and pterygium patients. The study used the Holladay IOL Consultant (Bellaire, Texas), which uses the Holladay II formula to calculate the toric correction required. Data was imported electronically to avoid transcrip- tion errors. IOLMaster ker- atometry (Carl Zeiss Meditec, Jena, Germany) was used for astigmatism axis and power, and A-constant was optimized/ personalized. Initially, the steep axis was marked with ink, but the proce- dure later progressed to using the Callisto digital marking system (Carl Zeiss Meditec), which improved results. From the perspective of surgical technique, it is import- ant to have very consistent sizing of the capsulorhexis. This ensures rotational stability and consistency with regard to effective lens position (ELP). In the study, surgeons used a 2.2-mm incision to minimize induced astigmatism. The IOL was implanted in the bag, aligned to the marked steep axis, and implantation was followed by thorough OVD removal. In terms of complications, two patients had radial tear in the capsulorhexis, but the IOL was implanted in the bag with no problems; five patients had cystoid macular edema that resolved with topical steroid and ketorolac. No patients had to return to the operating theater. In terms of spherical correction, with refractions ranging from +8.0 to –12.5 preop, surgeons achieved a mean absolute error of 0.30, median absolute error of 0.29, with a standard deviation (SD) of 0.36. In terms of cylinder cor- rection, over a broad range of preop refraction from 0 to –4.5, keratometric astigmatism of 0.60 to 4.33 requiring IOL toricity of 1.0 to 4.0, no patients had more than 1.0 D of residual astigmatism using digital mark- ing, and 98.6% had ≤0.5 D of residual astigmatism. Stratifying results showed a little bit of difference between with-the-rule (mean 0.14 D, SD 0.24, 98% with 0.5 D or less of residual astigmatism postop)

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