Eyeworld

EW CORNEA 32 November 2017 by Michelle Stephenson EyeWorld Contributing Writer from the lens versus the cornea, and I think that's helpful," he said. "The OPD-Scan III provides great Placido disk images, which I think is import- ant in understanding the regularity of the surface, and it gives you infor- mation about internal optics of the eye and wavefront. It also gives you angle kappa, which helps you deter- mine whether the line of sight is in line with the pupillary axis, and that has some implications in certain multifocal lens technologies. "The Pentacam is great for looking at the posterior cornea," Dr. Garg said. "It can provide a sense of the total corneal power and a nice image of the anterior chamber, so we can gauge if there's any angle compromise. It also provides objec- tive densitometry of the lens. [All of the devices] work a little differently, so having them all and being able to compare the numbers gives me checks and balances when it comes to trying to determine what I'm going to treat." Dr. Koch uses the Galilei and Cassini. "The Galilei has a Placido disk topographer and dual Scheimp- flug, so it provides great surface information, good astigmatism data, and corneal curvature data. It can be used to screen for keratoconus and other ectatic disorders. I think it is the ultimate all-in-one device, and it is an essential part of my practice," he said. "I am finding the Cassini increasingly valuable in astigma- tism planning because of its unique method of measuring total corneal astigmatism." Dr. Belin uses the Pentacam, and Dr. Ma noted that the best topographer on the market is a full gradient topographer, which uses dots instead of Placido disks. EW Editors' note: Dr. Belin has financial interests with Oculus. Drs. Garg, Koch, and Ma have no financial interests related to their comments. Contact information Belin: mwbelin@aol.com Garg: gargs@uci.edu Koch: dkoch@bcm.edu Ma: joseph.ma@utoronto.ca nus. If all we can see is the anterior surface, we will pick up keratoconus, but we will pick it up after the pa- tient has already lost some vision," he said. He noted that the devices that can provide this information are the Scheimpflug devices and to some extent OCT devices. Choosing a topographer According to Joseph J.K. Ma, MD, FRCSC, Toronto, Canada, all eye surgeons should have access to a good topographer based on reflec- tive technology. "A full gradient topographer, such as that available on the iDesign [Johnson & Johnson Vision, Santa Ana, California] or the Cassini [i-Optics, The Hague, the Netherlands], is the most accurate for small magnitudes of astigmatism; however, a Placido disk topographer is currently still considered the gold standard," he said. The Pentacam (Oculus, Wetzlar, Germany) can provide a good elevation map and is great for refractive surgery screen- ing; however, it is not as accurate for determining small degrees of astigmatism necessary for refractive cataract surgery. There are other combined topographers such as the Orbscan (Bausch + Lomb, Bridgewater, New Jersey), the Galilei (Ziemer, Port, Switzerland), and the Sirius (CSO, Florence, Italy) that provide excel- lent elevation as well as Placido disk information. The iDesign and the OPD-Scan III (Marco, Jacksonville, Florida) topographers combine wavefront and reflective topography. "We have eight topographers in my clinic, and each one has its own id- iosyncrasies," Dr. Ma said. "For angle and magnitude of astigmatism, the full gradient topographers are the most accurate; this is my primary to- pographer for determining accuracy in refractive surgery." Dr. Garg noted that some of the newer technologies, like the iTrace (Tracey Technologies, Houston) also provide a wavefront image. "I find that useful in understanding the to- tal optics of the eye. It will measure the wavefront aberration coming he said. "We routinely pick up subtle pathology that might not otherwise have been detected. It is essential for every cataract patient. You want to be able to inform your patients prior to or during the evaluation for cataracts exactly what you think the prognosis is from the front of the eye to the back of the eye. Topogra- phy is an essential part of that." Dr. Garg agreed and noted that he performs topography routinely on all cataract patients. "This is regardless of whether they have something that is billable. I want to see the quality of the astigmatism and the regularity of the surface," he said. "That helps to determine whether I have to treat their ocular surface disease and bring them back for additional measurements. If a pa- tient has a lot of astigmatism and he or she doesn't want a toric lens or an astigmatic incision, I can show the pre-existing astigmatism and explain that he or she will need to wear glasses postoperatively for some or all activities." According to Michael Belin, MD, Tucson, Arizona, topography also has an application in diagnos- ing early keratoconus. "While cur- rently the utilization of crosslinking in the United States is low, we need to be able to look at the posterior cornea to pick up early keratoco- It's a necessity for most ophthalmologists, especially those performing cataract and refractive surgery A ll ophthalmologists can benefit from having a corneal topographer in their practice. "It used to be a 'nice-to-have.' Now I think it's a 'need-to-have,' especially in our current state of cataract surgery," said Sam Garg, MD, University of California, Irvine. "With premium lenses, astigmatism management is increasingly critical in getting optimal outcomes. Even with monofocal lenses, the bar has been raised, and patients' expecta- tions are higher. If you're leaving behind astigmatism or not address- ing astigmatism, you're doing your patients a disservice." Uses Doug Koch, MD, Baylor College of Medicine, Houston, said he per- forms topography on all of his new patients. "I think it has become a fundamental part of the eye exam- ination, and I don't think you can have a sophisticated cataract practice today without a good topographer," Incorporating corneal topography into practice Device focus Irregular mires caused by epithelial basement membrane disease that was not diagnosed preoperatively and led to incorrect selection and alignment of toric IOL Source: Doug Koch, MD

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