CORNEA EWAP DECEMBER 2022 27 cornea. You want the patient to be perfectly centered,” he said. Tilt of the patient’s head should also be asessed. Even a 5- or 10-degree head tilt greatly affects measurement accuracy, Dr. Miller said. “Good technicians and good ophthalmologists will make sure the patient is perfectly centered vertically and horizontally, and they will also make sure they are aligned and not tilted,” he said. Even if the patient is positioned well on the X, Y, and Z axis, Dr. Miller said the tech needs to make sure they are looking in the right direction. He said it’s easy for patients to get distracted and look away, even if the instrument has a target for them to focus on. If patients are not looking at the target, Dr. Miller said it can result in measurements showing astigmatism or coma that does not exist. 2. Flag abnormalities and reimage, if necessary. Surface abnormalities (especially dry eye), contact lenses, cosmetic material, or debris in the tear film can “trip up measurements,” Dr. Miller said. If the measurements or imaging appears off, Dr. Miller said that the hope is that you will notice before the patient goes home so they can be reassessed. “I obtain all the imaging before they see me. If I see issues, I can send them back before they leave,” he said. Dr. Koch said to look for consistency (and inconsistency). “If you see inconsistency between two devices with regard to overall corneal power or astigmatic values, that’s a red flag that requires further investigation, and further measurements are needed, perhaps after more intensive treatment of the ocular surface to make the best recommendation and best choice for the patient,” he said. Dr. Koch said technicians at his practices are trained to look at the ease with which measurements can be obtained and any warning signals coming from the devices, for example, distortions in the mires produced from the Galilei. 3. Know when reimaging won’t improve results. Dr. Miller added that some corneas are irregular—those with Salzmann’s nodules or map-dot-fingerprint, for example—and will not improve with repeat imaging. The surgeon needs to know when repeat imaging won’t make a difference unless prior intervention is taken. 4. Get multiple measurements. Dr. Koch reiterated that his practice gets multiple measurements on different occasions, which allows him to look for consistency and inconsistencies. While he said that most surgeons aren’t getting two different measurements on two different occasions, he thinks it’s a best practice. “Surgeons who are doing refractive cataract surgery by and large are doing two different measurements, but I think it’s not common to do two different measurements and different measurements on different days,” he said. 5. Look at the total cornea. If you have access to a device that looks at both anterior and posterior surfaces, Dr. Miller thinks you should consider the total cornea in your IOL planning and not just the anterior surface. “I think a lot of people still use a biometer, an IOLMaster or Lenstar, to do their astigmatism planning,” Dr. This patient had LASIK in the days of the broad-beam laser. A central steep island of partially ablated cornea can be seen in the center of the map. This patient has a multifocal cornea and would not be a good candidate for a multifocal lens. This patient underwent LASIK almost 20 years earlier. The edge of the flap could not be seen on slit lamp biomicroscopy. The patient reported prior “eye surgery,” and the cornea was mapped with tomography.
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