EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/176967
46 EW FEATURE February 2011 Refractive challenges and innovations September 2013 Diagnostic curve balls by Michelle Dalton EyeWorld Contributing Writer AT A GLANCE • Advanced tomography should not replace clinical judgment. • When in doubt, repeat the test. • Err on the side of caution. • Advanced topography can identify more than just potential dry eye. When topography or tomography show a warning sign, what should you do? D iagnostics are an invaluable tool for surgeons— especially when patients are choosing an elective procedure such as laser vision correction, where outcome expectations are heightened. Technology provides critical information, but there are times when technology may not match up completely with what a clinician sees. "In my mind, I am always trying to match the evidence with the clinical situation," said Y. Ralph Chu, MD, Chu Vision Institute, Bloomington, Minn. When those situations do occur, "repeat the test," said Carlos Buznego, MD, Center for Excellence in Eye Care, Miami, and voluntary assistant professor of ophthalmology, University of Miami's Bascom Palmer Eye Institute. "Whenever I get a bizarre reading on a topography, the first thing I do is repeat the test." Vance Thompson, MD, director of refractive surgery, Vance Thompson Vision, Sioux Falls, S.D., is a "big believer in being sensitive to your diagnostic devices. This is elective surgery—and it's OK to approach it conservatively." Always thinking about the standard caveat to "Do no harm," while LASIK has a success rate of "more than 99%, there is always a risk, same as with any surgical procedure," said Uday Devgan, MD, in private practice, Los Angeles, and chief of ophthalmology, Olive View – UCLA Medical Center. "So if your tomography comes back suspicious, you need to pay attention to that." Some centers will only use tomography, while others pay closer attention to topography. "While tomography offers a very detailed analysis, one of the clear messages from earlier studies is that the most important screening tool for patients who might develop ectasia is topography. It can be very confusing," said Lou Probst, MD, chief laser surgeon and senior medical advisor, TLC The Laser Eye Centers (locations in Chicago; Madison, Wis.; and Tampa, Fla.). "I think in the effort to make a great diagnostic tool, Oculus [Wetzlar, Germany] created a great diagnosis tool in the Pentacam." Pentacam flag: The overall yellow D flag suggests that PRK may be the best option despite thick corneas with high astigmatism but no obvious inferior steepening. Source: Lou Probst, MD An example of inferior steepening of the left eye Source: Uday Devgan, MD In comparison, an example of a normal cornea in the right eye Source: Uday Devgan, MD The Pentacam analyzes five subcategories of a patient's eye and if it detects an anomaly will produce a yellow or red flag, Dr. Probst said. "The machine has become so analytical and provides so much information it is actually altering the outcome of clinical practice." He said it's not unusual to see a patient with good topography and no clinical issues, yet the Pentacam will show a yellow flag or two. Dr. Chu said he takes a more conservative approach as well, by either suggesting PRK or recommending against LASIK when those flags are raised. He'll even recommend some patients wait altogether "because there may be a time when diagnostic technologies will improve to where we can get a definitive answer" about the anomalies. Dr. Thompson added a patient's level of refractive error will help sway his preference as well; a –1 or –2 D will "may not alter" his comfort level with LASIK, but for refractive errors and diagnostics that push a patient into a borderline scenario, "why not just do what leaves the cornea stronger? I'll recommend PRK, since it also minimizes complications like ectasia." Other cases—a moderate myope with suspicious looking, against-the-rule cylinder "and you start to wonder if either treatment makes sense," he said, especially if the surgeon is comfortable implanting a phakic IOL. As Dr. Buznego quoted a colleague of his: "Patients are always their disease until you operate on them. Once you've operated, it's now your disease to manage and control."