EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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we've never gotten down to where we've been worried about 0.5 diopter of cylinder," he said. "It's now getting down to the level where we're beginning to realize that if we want to get it perfect, we've got to compensate for those, too." E ffective lens position Can the precision of femtosecond technology translate into better results? Whether or not IOLs can b e better positioned as a result is the key consideration here, Dr. Donnenfeld said. He views the effective lens position as a missing link to achieving optimal results with cataract surgery. "Knowing where the lens is going to sit after cataract surgery is the key to achiev- ing good refractive results," he said. H e added that with biometry now so good, the advantage of the arc of the femtosecond capsulotomy is that it makes the same size capsulotomy every time. As a result, the thinking is that the lens is less likely to vault forward because the capsulotomy is too large or that the lens will be trapped and pulled backward. "There have been several studies showing this improves effective lens position and one study I know of showing it did not," Dr. Donnenfeld said. "In my estimation, I don't think there's any way the femtosec- ond laser can degrade effective lens position—it can only help." He thinks he is getting tighter results with femtosecond laser capsulo- tomies. However, he stressed, studies need to be done on where such capsulotomies need to be placed for best outcomes. "We're still worrying about where the best place to put these capsulotomies is," Dr. Donnenfeld said. Dr. Holladay pointed to a study he presented at the 2013 European Society of Cataract & Refractive Sur- geons Congress that examined if the location and diameter of the capsu- lorhexis that are made absolutely consistent because of the precision of the laser shows up in prediction error. He reported that for + or –0.25 D of prediction error with the LenSx laser (Alcon, Fort Worth, Texas), that was about 20% better than the Optiwave Refractive Analysis, which was 10% better than standard cataract surgery at one month. Dr. Koch thinks the jury is still out on whether the femtosecond laser helps with effective lens posi- tion. "I think the next step where femtosecond lasers will be more beneficial will be when we have lens implants that are designed to take a dvantage of that very predictable size and location and [we can] attach lenses in a different way," Dr. Koch said. "I think then we will see a benefit from the effective lens position." Dr. Alpins concurs. "It would be nice to be able to say that it's more predictable and more accurate be- c ause then you're going to get better outcomes," he said. "But in the hands of experienced surgeons that hasn't been shown to be the case." He stressed that the accuracy refrac- tively is no better than that attained by an excellent cataract surgeon. "[For a] less than excellent cataract surgeon, femtosecond technology m ay significantly help by giving consistency to their surgery that their own manual techniques are not giving them," Dr. Alpins said. Additional tools Pairing the femtosecond laser with other tools can also potentially help to boost outcomes. Dr. Donnenfeld noted that the Verion (Alcon) allows surgeons to account for cyclorota- tion of the eye at the time of surgery that could improve outcomes. "That allows you to take preoperative pictures of the eye and then overlay them at the time of surgery," he said. However, he thinks using the Optiwave Refractive Analysis in conjunction with surgery is the best way to get a true reading of the actual cylinder. "The advantage of the Optiwave Refractive Analysis is that not only does it measure the anterior cylinder, it also measures the posterior corneal cylinder as well," Dr. Donnenfeld said, adding that getting such a true reading allows the practitioner to adjust cylinder very precisely. He finds this helps for toric IOLs as well, pointing out that the Optiwave Refractive Analysis tells the practitioner where to rotate the axis and whether or not to open an incision at the time of surgery to achieve an optimal result. "I think that intraoperative readings are the only way we're going to always achieve the next level of accuracy with cylinder control because the variables of the visual axis, posterior corneal Operating continued from page 112 108-125 Feature_EW March 2014-DL2_Layout 1 3/6/14 3:59 PM Page 114