Eyeworld

EW SECONDARY FEATURE 120 March 2015 by Ellen Stodola EyeWorld Staff Writer treatment for keratoconus or anoth- er condition, the surgeon may want to perform this prior to the toric lens in order to "lock in" whatever astigmatism is there, Dr. Koch said. Intraoperative aberrometry Intraoperative aberrometry is the "third piece of the puzzle," Dr. Koch said. This is helpful if there is any question or variability in measure- ments. He obtains at least 3 measure- ments preoperatively. These include the LENSTAR (Haag-Streit, Koniz, Switzerland) or IOLMaster (Carl Zeiss Meditec, Jena, Germany), the Cassini, and a GALILEI image (Ziemer, Port, Switzerland). The GALILEI and Cassini give posterior corneal measurements that are eval- uated for further accuracy as well, he said. "Refraction is a fourth piece of important preoperative data (some- thing I learned from Robert Cionni, MD): It can give clues to posterior corneal astigmatism. "With those 4, if there's some disparity among them, then cer- tainly the ORA [Alcon, Fort Worth, Texas] can play a helpful role." Other systems in the space include the Holos IntraOp Wave- front Aberrometer (Clarity Medical, Pleasanton, Calif.) and imaging modalities including Callisto Eye with Z-Align (Carl Zeiss Meditec), the iTrace with Zaldivar Toric Cali- per (Tracey Technologies, Houston), TrueGuide software (TrueVision), and the VERION Digital Marker (Alcon). If there is any question about lens selection, use the ORA at the time of surgery for IOL magnitude of toricity and actual alignment, he said. "We find it helpful," Dr. Koch said. "It's not perfect, but it's certain- ly helpful." EW Editors' note: Dr. Koch has financial interests with Abbott Medical Optics (Abbott Park, Ill.), Alcon, i-Optics, TrueVision, and Ziemer. Dr. Hardten has financial interests with Abbott Medical Optics. Contact information Hardten: drhardten@mneye.com Koch: dkoch@bcm.edu difficult to wear contact lenses for the irregular astigmatism postopera- tively," he said. It can be difficult to determine if patients with irregular astigmatism can still be candidates for toric IOLs, Dr. Koch said. "Certainly there are many patients who are not candidates for toric IOLs," he said. "It depends on the severity of the irregular astigma- tism." In order to determine how this factor weighs in, Dr. Koch said a good estimate could be made based on the patient's corneal topography. Additionally, the patient's history of glasses can play a role in helping a physician decide. If patients were wearing glasses with astigmatism correction and had reasonable vision before the cataract, then correcting astigmatism with a toric lens should be helpful for them, he said. With other issues, particularly keratoconus, a surgeon needs to know whether the irregular astig- matism will remain stable. First, Dr. Koch said, it is important to determine if the condition could be treated initially. Second, he said it is important to figure out if it is stable or not. A keratoconus patient who is a contact lens wearer may not be the best candidate in this case. Ad- ditionally, should the patient need This method has turned out to be helpful, he said. Using the fem- tosecond laser marks also helps to determine how accurate the manual marks are. When he places the IOL in the final position, Dr. Koch said, he makes a note of how far off the femtosecond laser marks are from the manual marks and uses this to monitor the IOL position postoper- atively. "It makes for a very complete, meticulous way to record everything that's taking place," he said. Marking the axis to place the IOL is still a difficult task, Dr. Hardten said. Currently, he uses the image of the eye from topography, matching the cylinder and looking for landmarks. There are also newer options that seem to be helpful, he said, like intraoperative aberrometry. "Marking preop at [12 o'clock and 6 o'clock] may be helpful, but not as accurate," he said, as it may be difficult to get the marks directly at 12 and 6 o'clock. Patients with irregular astigmatism Dr. Hardten said he prefers not to use these IOLs in patients with irreg- ular astigmatism, unless they tradi- tionally had good vision in glasses and their topography is regular. "The results are much more challenging, and it makes it very Toric IOLs are a valuable option, but careful consideration should be taken when selecting these lenses T oric IOLs can be a good option for a number of patients; however, careful patient selection is import- ant. There are a number of technologies that can help this process go smoothly for both the surgeon and the patient. David Hardten, MD, Minnesota Eye Con- sultants, Minnetonka, Minn.; and Douglas Koch, MD, professor and Allen, Mosbacher, and Law chair in ophthalmology, Cullen Eye Insti- tute, Baylor College of Medicine, Houston, weighed in on the topic. Good candidates Dr. Hardten said that patients with regular astigmatism and those interested in reducing dependence on glasses when they have cataract surgery are good candidates for toric IOLs. These patients should have an otherwise healthy eye. Dr. Koch said that he will usu- ally implant these lenses in patients who have around a diopter and a half or more of anticipated astig- matism after cataract surgery and who desire good uncorrected vision. Unfortunately, there is a financial issue to consider as well, because of the cost to patients. Marking the axis to place the IOL "Every patient gets marked," Dr. Koch said. "Those marks are then used to place femtosecond laser incisions along the meridian of IOL alignment." Dr. Koch uses the Cassini (i-Optics, The Hague, the Nether- lands) corneal analyzer and the TrueVision 3D Surgical System (Santa Barbara, Calif.), which help to line up the IOL. "Corneal topography image and conjunctival vessels are record- ed using the Cassini, and we then develop a surgical plan with their software," Dr. Koch said. "We take that into the operating room and using the TrueVision system, we can detect the correct meridian along which to align the IOL." Toric IOL considerations The Baylor toric IOL nomogram provides a way to account for posterior corneal astigmatism. The astigmatic values shown in the middle and right columns of the table are the vector sum of the measured anterior corneal astigmatism and the surgically induced astigmatism. Source: Douglas Koch, MD

• Cover