Eyeworld

OCTOBER 2020 | EYEWORLD | 35 C by Maxine Lipner Contributing Writer Optimizing manual small incision cataract surgery outcomes Dr. Vann and co-investigators found, however, that this had minimal effect. "Despite my thinking about the white-to-white, at least in small incision cataract surgery where I was trying to make my incision very close to the limbus, whether it was temporally or supero- temporally, this did not have any association," Dr. Vann said, adding that other factors such as preoperative existing astigmatism, preoperative IOP, central corneal thickness, absolute length, number of paracentesis incisions, or the axis of the main incision weren't statistically significant either. In this study, incisions were kept to 2.2 mm. However, in cases where they are slightly larger, astigmatism may be a factor. Dr. Vann cited a previous study 2 that suggested that white-to- white diameter of the cornea did influence the surgically induced astigmatism. "In the study, they were doing their incisions superotemporal- ly or superonasally, making 3 mm incisions," he said. "They were operating closer to the visual axis and they were using a larger incision." Many think that incisions under 2.5 mm tend to be relatively neutral in terms of overall impact M anual small incision cataract surgery (MSICS) is a skill every cataract surgeon should learn, according to Susan MacDonald, MD. It gives a surgeon options and confidence to handle several complex cases, she said. With MSICS, there is limited risk to endothelial cells or dropping of the nucleus or fragments. Most importantly, it provides an excellent result with- out expensive technology, Dr. MacDonald said. There are several ways to maximize outcomes with this technique that is more commonly employed in areas where phaco is not a viable option. Minimizing astigmatism To maximize MSICS outcomes, is important to make an effort to minimize astigmatism. Dr. MacDonald stressed paying attention to pre- operative astigmatism; it is possible to reduce astigmatism with the placement of the incision on the steep axis, she said. In a low resource setting, the Maloney Astigmatism Keratometer can help the surgeon evaluate the shape of the cornea at the beginning and end of the pro- cedure. This will help the surgeon decide if a suture could help by placing it on the flat axis, she said. If using a scleral incision, this could be placed further away from the cornea where it will be less astigmatism-inducing. Reducing the size of the incision may help as well. Dr. MacDonald suggested modifying the MSICS using the miLOOP (Carl Zeiss Meditec) to create a 5 mm mini MSICS, a smaller incision, which can affect astigmatism. A recent prospective study considered another factor in minimizing astigmatism in MSICS: white-to-white measurements. 1 "We were trying to get a better handle on treating astigmatism," said Robin Vann, MD, adding that when planning for small amounts of astigmatism with MSICS there were occa- sions where he was getting astigmatic surprises. He thought that possibly, akin to previous RK, arcuate, and limbal relaxing incisions, the closer these were to the visual axis, the greater their impact. continued on page 36 About the doctors Susan MacDonald, MD Associate Clinical Professor Tufts University School of Medicine Boston, Massachusetts Robin Vann, MD Associate Professor of Ophthalmology Duke University Durham, North Carolina References 1. Zhang W, et al. Influence of corneal diameter on surgically induced astigmatism in small- incision cataract surgery. Can J Ophthalmol. 2019;54:556–559. 2. Theodoulidou S, et al. Corneal diameter as a factor influencing corneal astigmatism after cataract surgery. Cornea. 2016;35:132–136. Relevant disclosures MacDonald: Carl Zeiss Meditec, Perfect Lens Vann: Alcon Contact MacDonald: susanmacdonaldeyecorps@ gmail.com Vann: Robin.Vann@duke.edu Mature white cataract; small incision cataract surgery is performed by creating a 7–8 mm curvilinear half thickness scleral incision; the crescent blade is used to continue this incision forward, creating a pocket; the incision begins 1.5–2 mm posterior to the limbus, and the pocket is made into the clear cornea by 1.5 mm Source: Susan MacDonald, MD

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