Koch, MD, professor and Allen, Mosbacher, and Law This question is one of the few that evokes a range of opinions from the experts. “Surgeons who are still using the earlier-generation formulae can certainly do better for their patients.”Ģ Should I plug my numbers into multiple formulas and compare the results? “There’s good data to show that the latest generation of formulae, whether it’s mine, the Olsen, Hill-RBF or Holladay II, outperform the earlier generation of formulae,” he says. Barrett, MD, a clinical professor of ophthalmology at the Lions Eye Institute and the University of Western Australia, consultant to the ophthalmology department at Sir Charles Gardiner Hospital, in Perth, Australia, and creator of the Barrett Universal II formula, agrees. We should always strive for what’s achievable.” “We’re all creatures of habit, but fortunately, surgeons are beginning to switch to the newer formulas-what we jokingly refer to as ‘formulas from this century.’ An 80-percent ☐.50 D accuracy level is acceptable, but 90-percent ☐.50 D accuracy is now achievable. “This is a huge sea change in the accuracy of lens-power calculation,” he notes.
Two or three years ago, only 1 or 2 percent of surgeons achieved that now everybody can potentially reach that level. “We’re starting to see physician databases in the 90-percent range. “Now, as we begin to see the newer biometers and newer formulas, like the Barrett and Hill-RBF, being used by surgeons who also take their time making the measurements and then apply validation criteria, that’s changing,” he continues.
That’s what most people achieve using the older formulas.
So 71 to 80 percent is sort of the acceptable range. Different studies around the world have found rates ranging from 55 to 80 percent. Fewer than 1 percent of surgeons in that database are at 92 percent or better. “Six percent of surgeons are at 84 percent or better. “After the removal of outliers, and following lens-constant optimization, the average ophthalmologist gets about 78 percent of patients within ☐.5 D of the target refraction,” he says. Hill, MD, medical director of East Valley Ophthalmology in Mesa, Arizona, and creator of the Hill-RBF formula, is in a unique position to compare the outcomes of surgeons using old or new formulas, since he’s reviewed data from more than a quarter-million surgeries (mostly calculated using the older formulas). To understand how much difference switching to a more advanced formula can make, it’s important to look at outcomes. Most surgeons today are aware that the more recent formulas are capable of producing more accurate power predictions than the older formulas, yet many surgeons continue to use the older ones. With that in mind, four experts in this area, all known for their work developing IOL power formulas, share their answers to 10 questions a clinician might ask about these formulas, covering issues such as how they work how best to use them and what the future may hold.ġ Is it so bad to just keep using the older formulas?
Nevertheless, the better we understand something, the more likely we are to use it to its best advantage. Understandably, most surgeons like being able to simply plug numbers into a machine or an online calculator that does the work and produces an answer, without the surgeon having to worry about the details. Nevertheless, these formulas are an essential part of performing cataract surgery. As at least one expert has noted, creating and improving upon these formulas is a job best managed with the help of physicists, mathematicians and optical engineers. Few subjects in the field of ophthalmology are as complex as the formulas surgeons use to predict the best intraocular lens power for a given patient.
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