EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/357599
EW FEATURE 36 Keratorefractive surgery August 2014 • Surgeons are constantly searching for the most accurate formula(s) and tools to assist with post-myopic LVC IOL selection. • The ASCRS IOL calculator is a popular destination that enables surgeons to use various IOL formulas. The Barrett True K formula on the Asia-Pacific Association of Cataract & Refractive Surgeons website is also becoming more well known. • Some formulas that have proven accurate include the Masket/Masket Modified, Haigis-L, and Shammas. • Intraoperative aberrometry has led to more accurate IOL calculations, although surgeons still would like a way to better address effective lens position. by Vanessa Caceres EyeWorld Contributing Writer you think it has some clinical "logic" to it, he cautioned. In addition to the ASCRS IOL calculation website, there is a web- site used in Australia and Asia that may start to garner more attention in the U.S., Dr. Hill said. The website of the Asia-Pacific Association of Cataract & Refractive Surgeons (apacrs.org) features a menu with a tab labeled "IOL Formulae." Under that tab, surgeons will find the Barrett True K formula, which Dr. Hill said he has been using frequently for both myopic and hyperopic LASIK. "In my practice, I see a lot of people with previous refractive surgery sent to us from around the country, so I try to have as many tools in my toolbox as possible," he said. Determining which formula to use Despite a plethora of formulas avail- able to use for post-myopic LVC IOL calculation, some studies and clin- ical experience consistently show specific formulas to be the most ac- curate, said Samuel Masket, MD, in private practice in Los Angeles, and clinical professor of ophthalmology, Jules Stein Eye Institute, David Gef- fen School of Medicine, University of California, Los Angeles. If the specific prior laser vision correction treatment is known, the Masket formula (invented by Dr. One way that Mark Packer, MD, Bowie Vision Institute, Bowie, Md., uses the site is by inputting all available data. The calculator inevitably returns a range of IOL powers, often exceeding 2 D, he said. "I pull all of these IOLs into the OR on the day of surgery. There is literally a plastic bucket full of IOLs on the counter," he said. Dr. Packer then uses the ORA (WaveTec Vision, Aliso Viejo, Calif.) intraoperative aberrometry aphakic measurement to determine the specific IOL to implant. The vast majority of the time, the ORA recommendation falls within the range of IOLs he has ready to use. If not, he uses the IOL at the end of the range closest to it. "With this method, so far I have achieved 100% 20/40 or better post- operative uncorrected visual acuity. This has greatly reduced the need for postoperative enhancement procedures such as additional LASIK, PRK, or piggyback IOLs," he said. To maximize use of the ASCRS site, Dr. Koch recommends getting as many measurements as possible with different devices. Most sur- geons ignore the clinical history in the left column and focus on the middle and right columns. "I think finding an overall average value from the middle and right column will probably prove to be the most accurate reading," Dr. Koch said. If you get an outlier, be wary unless Tracking the best way to select IOLs after myopic laser vision correction S electing the right IOL for a patient after myopic laser vision correction (LVC) can be a tricky task— and there is still room for improvement. "We're not at a point where we are matching the outcomes in virgin eyes," said Douglas D. Koch, MD, professor and the Allen, Mosbacher, and Law chair in ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston. "If anything, we want more accurate results in these patients because that's why they elected to have LASIK in the first place." Surgeons may use different tools and formulas for their post-refractive surgery IOL calculations, but they all have one goal in mind—to find the most accurate IOL for the patient. Here's how some anterior segment surgeons approach it. A little help from reliable websites The IOL power calculation website sponsored by the ASCRS Foundation (iolcalc.org) has become a handy tool for surgeons to input patient data and try different formulas, said Dr. Koch, who is one of the site's creators. As of March 31 this year, the site had received 110,000 hits in 12 months. The site is widely used around the world and is open to all surgeons, even if they are not ASCRS members. Every month, site creators review the ever-growing literature related to post-refractive surgery IOL calculations to evaluate if there is something new worth adding to the site, said site co-creator Warren E. Hill, MD, East Valley Ophthal- mology, Mesa, Ariz. Any formulas or information they consider adding must first be published in peer- reviewed journals or presented at national or international meetings with committee oversight, he said. "There are so many calculation methods that come out, only the ones that subsequently stand up to the test of independent validation are candidates for inclusion," he said. Targeting accuracy AT A GLANCE Barrett True K formula for prior myopic or hyperopic LASIK/PRK Source: Asia-Pacific Association of Cataract & Refractive Surgeons