Eyeworld Supplements

by Elizabeth Yeu, MD Correcting astigmatism at the time of cataract surgery EW San Diego 2015 2 Please refer to pages 7 and 8 for important product information about the Alcon products described in this supplement. M ost Americans have some refractive astig- matism, and upward of 40% have more than 1.0 D of corneal astig- matism. Toric lenses are continuing to gain popularity and are an ideal choice for patients with higher levels of astigmatism who desire reduced spectacle dependence after cata- ract surgery. I perform astigmatism correction in half of my cataract sur- geries. Of my overall cases, 10–25% of my total volume is toric IOLs. I typically correct astigmatism using arcuate incisions or toric IOLs, and arcuate incisions can more accurate- ly correct upward of 1.25 D of total corneal astigmatism. For those with visually signifi- cant astigmatism (more than 1.0 D), spectacle independence is the main reason to correct astigmatism with a toric IOL as opposed to LRIs, and spectacle independence is a hugely attractive benefit to these patients because most have never been able to see clearly without glasses or contacts. Patients with higher levels of astigmatism are often drawn to toric IOLs, and the adoption of this technology happens with little hesi- tation because patients recognize my enthusiasm for and endorsement of it. Once a relationship is established, they often trust me to help guide their decision process. I know that patients will have a higher-defini- tion type of vision postoperative- ly. Patients with higher levels of astigmatism should consider toric IOLs because if left uncorrected at the time of cataract surgery, they will require prescription spectacles postoperatively for the rest of their lives, which can be an expensive proposition. Toric IOL surgery has brought to light how little we once knew and understood about astigmatism management prior to the availability of accurate toric technology. Pre- toric IOL utilization, inaccuracies and the unpredictable outcomes were attributed to the actual un- predictability of arcuate incisions in and of themselves. Once toric technology platforms came about and we were able to nail the corneal astigmatism, that's when a lot of other things came into play, in- cluding the importance of effective lens position as well as total corneal astigmatism and the contribution of the posterior cornea to it. Successful toric IOL surgery comes down to 3 steps: accuracy of preoperative measurements of the corneal astigmatism, proper steep meridian identification during cataract surgery, and technique to ensure stability of the IOL's position. It is important to be as accurate as possible because for every degree that the lens is off, the patient loses 3.3% of astigmatism correction. As an example, if the toric IOL is off by just 10 degrees, it causes a 33% loss in desired astigmatic effect and a potentially unhappy postoperative patient. There are several ways to measure the axis of astigmatism. I identify the total corneal astigma- tism with the Cassini (i-Optics, The Hague, the Netherlands), which is able to more accurately determine the astigmatic contribution of the posterior cornea. The LENSTAR biometry (Haag-Streit, Koniz, Switzerland) provides beautiful anterior K values, and I verify that with another topography device. We have the Atlas (Carl Zeiss Meditec, Jena, Germany) and the Nidek OPD (Fremont, Calif.), but I generally will use the OPD because it also offers angle kappa information. Additionally, there are sever- al methods for marking the axis of astigmatism, and they vary in accuracy. The standard of care for marking the axis has been ink, but ink pens are not ideal because of the precision required for both measuring and marking the target axis. Marking at the slit lamp and/ or incorporating various astigmatic tools to identify the reference axes and align the steep meridian can increase accuracy. Other methods include imaging or fingerprinting, limbal registra- tion, and wavefront intraoperative aberrometry. We also employ the Verion System (Alcon). While it takes time to initially get comfortable incorpo- rating the Verion System into the practice, once it is incorporated, I believe this technology will con- tinue to improve and make toric surgery faster because the reference landmarks have already been identi- fied. Intraoperatively, you no longer have to ink mark the steep merid- ian on the cornea beyond image registration of the eye, as the Verion System projects this onto the cornea. Preoperatively, the Verion System re- quires an extra image capture for the surgical planning. Intraoperatively, this does help to increase efficiency and accuracy with toric IOL surgery. Dr. Yeu is in private practice in Norfolk, Va., and assistant professor at Eastern Virginia Medical School. She can be contacted at eyeu@vec2020.com. " Successful toric IOL surgery comes down to three steps: accuracy of preoperative measurements of the corneal astigmatism, proper steep meridian identification during cataract surgery, and technique to ensure stability of the IOL's position " The visual impact of astigmatism Elizabeth Yeu, MD

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