Eyeworld

EW CATARACT 32 December 2015 by Maxine Lipner EyeWorld Senior Contributing Writer Also, devices such as the iTrace (Tracey Technologies, Houston) can help practitioners determine where the center of the bag is in relation to the patient's line of sight, something that may be important in deciding which lens to implant in these cases. "We can help determine, based on where the center of sight is and where the center of the bag is, which technologies may be ruled out for patients," Dr. Shultz said. "With the iTrace, we can analyze both wave- front aberrometry and topography to determine which higher-order aberrations are coming from the cornea and which are coming from the lens." Selecting post-LASIK IOLs Because the post-LASIK eye can be aberrated, selecting which lens to implant can be tricky. Dr. Jackson pointed out that myopic PRK or LASIK cases usually have positive spherical corneal aberration, whereas hyperopic treatments typically have the aphakic mode," Dr. Jackson said. With the Haigis-L alone, he has found that approximately 85% of patients are within 0.5 D of targeted refraction, but when this is com- bined with the ORA, more than 90% hit this mark. Dr. Shultz pointed out that even if you don't have the patient's pre- LASIK measurements, practitioners generally have an idea of how exten- sive a treatment was based on their current keratometry readings. Also, you can look at the symmetry of the cornea and its uniformity, particu- larly for those who have undergone myopic LASIK. "For patients who have slightly decentered ablations, we certainly have to be concerned about the potential for postoperative issues with higher-order aberrations associated with the cornea," Dr. Shultz said. "With hyperopia, again centration is critical in trying to anticipate any potential problems a patient might have postoperatively with almost any lens that we use." Because traditional formulas are inaccurate, practitioners should use more current generation formulas that don't rely on corneal powers, Dr. Jackson explained. He uses the IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany) to obtain biometry readings, adding that this and sim- ilar devices have 4th- and 5th-gen- eration IOL calculation formulas such as the Haigis-L. Unlike with the traditional clinical history method, with the Haigis-L you don't need to know what the patient's preopera- tive K readings were before LASIK. "All you need to know with Hagis-L is if a patient had a myopic or a hy- peropic PRK or LASIK," Dr. Jackson explained, adding that most patients know which laser vision correction procedure they had or at the very least whether they had trouble see- ing up close before surgery or not. He also fine-tunes the calcula- tion using intraoperative aberrom- etry with the ORA System (Alcon, Fort Worth, Texas). "This gives real-time readings on the table in Succeeding at cataract surgery after LASIK M any cataract patients these days are among the rising tide of those who have already undergone LASIK, according to Mitch Shultz, MD, Northridge, Calif. "Since we're 20 years into the LASIK market in the U.S., we're definitely starting to see more and more post-LASIK and certainly post-RK patients who are possibly even 30 years out from these surgeries," Dr. Shultz said. These patients present a unique set of challenges. He finds part of the problem is too often such patients don't have any of their pre-surgery measurements. "Often that information isn't available because many doctors have either stored or destroyed those records," Dr. Shultz said. "One of the practic- es we've just started instituting is providing our LASIK patients with a LASIK K card where we give them a piece of paper with their preop- erative refraction, as well as their preoperative keratometry readings." The hope is that they'll save this in- formation and be able to access it at some point when they need surgery in the future, he explained. Current measurement quandary Unfortunately, most patients coming in today don't have that information that can help to make surgical planning easier. "It definite- ly helps with the various post-re- fractive surgery calculators that are available to the surgeon," Dr. Shultz said. "The one that I use most is the post-refractive surgery calculator available on the ASCRS website." Mitchell A. Jackson, MD, founder and CEO of Jacksoneye, Lake Villa, Ill., also finds that too often post-LASIK patients don't have their preoperative measurements. "The problem is you can't get an accurate corneal reading," he said. "Standardized keratometry readings will not work in the sense that you'll be inaccurate and will get a hyper- opic surprise most of the time." This is the last thing you want in a cataract patient, he said, adding that he would rather be right on target in these patients or even leave them a little myopic. On the refractive rebound The Haigis-L formula doesn't require clinical history or contact lens over-refraction, but it can only be used for prior laser-based refractive surgeries. Select whether the patient had myopic or hyperopic correction, and go through the usual calculation procedure. Source: Mitchell A. Jackson, MD

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