Eyeworld

34 | EYEWORLD | SEPTEMBER 2022 by Ellen Stodola Editorial Co-Director About the physicians Cathleen McCabe, MD Medical Director The Eye Associates Bradenton, Florida Steven Schallhorn, MD Professor of Ophthalmology University of California San Francisco San Francisco, California BACK TO BASICS ATARACT C combining both the anterior and posterior cornea components," he said. "This is especially important if the corneal shape has been altered, such as patients who have undergone laser vision correction." Dr. McCabe said that this is an important topic, particularly because many people find it intimidating. She stressed that one of the most important things is to ensure the health of the ocular surface when performing and analyzing measurements. "I think the simplest thing is to carefully examine the patient. During the cata- ract evaluation, some practices will do biometry, topography, Ks, and axial length on the same day," she said. "If you do that, make sure you do it at the beginning before anything has touched the eye. What we decided to do is separate those visits, so we can make sure that every pa- tient is at least using lubricating drops prior to biometry and has a greater likelihood of having an ocular surface that is pristine and not dry." For accurate measurements, Dr. McCabe suggested having a way to reliably and accu- rately obtain the corneal curvature/Ks, noting there are several technologies for this. She Factoring astigmatism into cataract surgery decisions continued on page 36 I n the spirit of the "Back to basics" theme of this issue, Steven Schallhorn, MD, and Cathleen McCabe, MD, discussed the important topic of identifying astigmatism prior to cataract surgery: how to determine the level of astigmatism, when to address it, and how even low levels may have an impact. Dr. Schallhorn said the most important thing is taking the time to measure the corneal astigmatism. "That's the critical component," he said, adding the clinicians might get tripped up if they don't see much astigmatism in patients' glasses and choose to disregard it. "If a patient has very little astigmatism in their prescrip- tion, eyecare providers often don't think about measuring corneal astigmatism, so that is the most important basic element," he said. "The act of measuring is the most important first step." A patient can have a diopter or less of manifest astigmatism and have much more than that in corneal astigmatism. The corneal astigmatism primarily determines the post-cataract proce- dure manifest astigmatism. As far as measuring goes, Dr. Schallhorn said there is great technology for this. "We can now measure the total power of the cornea, 83.7% 77.4% 68.5% 50.8% 36.1% 18.6% 8.9% 4.3% 9.1% 54.4% 47.1% 32.9% 18.7% 10.4% 4.2% 0.5% 0.0% 1.8% 0% 25% 50% 75% 100% 0 0.25 0.5 0.75 1 1.25 1.5 1.75 >=2.0 % of eyes Residual manifest astigmatism 20/20 UCDVA 20/16 UCDVA This figure demonstrates the relationship between manifest astigmatism and uncorrected distant visual acuity at 3 months postop for 13,267 dominant eyes implanted with a multifocal IOL. This shows even low levels of astigmatism affect unaided vision. Source: Steven Schallhorn, MD 83.7% 77.4% 68.5% 50.8% 36.1% 18.6% 8.9% 4.3% 54.4% 47.1% 32.9% 18.7% 10.4% 4.2% 0.5% 0.0% 0% 25% 50% 75% 100% 0 0.25 0.5 0.75 1 1.25 1.5 1.75 % of eyes Residual manifest astigmatism 20/20 UCDVA 20/16 UCDVA

• Cover