EyeWorld Asia-Pacific September 2016 Issue

September 2016 34 EWAP FEATURE AT A GLANCE • LRIs are generally used for correcting 1.5 D or less of astigmatism. • Toric IOLs work best for perfectly symmetric astigmatism; for asymmetric corrections, use an LRI if the cornea is otherwise stable. • LRI nomograms must be age- and pachymetry-adjusted. Limbal relaxing incisions versus toric IOLs for astigmatism correction by Lauren Lipuma EyeWorld Contributing Writer Surgeons discuss the pros and cons of each treatment O phthalmologists have two options for correcting astigmatism at the time of cataract surgery: limbal relaxing incisions (LRIs) and toric IOLs. Most surgeons agree that LRIs are best for small amounts of astigmatism and toric IOLs for larger amounts, but where exactly the line is drawn between them is still a matter of debate. Each method has advantages and disadvantages, and there are various factors to take into account when deciding which technique to use. Here, experienced refractive cataract surgeons Uday Devgan, MD , clinical professor of ophthalmology, Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, chief of ophthalmology, Olive View UCLA Medical Center, and in private practice, Devgan Eye Surgery, Los Angeles; D. Rex Hamilton, MD , clinical professor of ophthalmology and director, UCLA Laser Refractive Center, Los Angeles; and Jeffrey Whitman, MD , Key-Whitman Eye Center, Dallas, Texas, discuss the pros and cons of each method and the factors that play into their decisions when choosing which option to use. When are LRIs best? LRIs are generally best for correcting low amounts of astigmatism—around 1.5 D or less, according to the doctors. “For 1.5 D or more of corneal astigmatism, toric IOLs will provide a more accurate and more stable refractive correction,” Dr. Devgan said. However, if a patient has an affordability issue with a toric lens, Dr. Whitman will treat up to 2 D of astigmatism with LRIs, but only if it is symmetric. “If there is irregularity in the topography, I lean toward toric lenses and certainly if there is more than 1.5 D of astigmatism,” he said. Both methods have strong safety records, but are slightly different in efficacy, according to Dr. Devgan. While toric IOLs are effective across a full range of corrections—from 1 to 4 D—the efficacy of LRIs is more variable, he said. LRIs work well for lower degrees of correction, such as 0.5 to 1.25 D of corneal astigmatism, but become less predictable and less accurate at higher corrections. “Attempting to do a 3 or 4 D AK/LRI is not likely to give good results and may even lead to destabilization and irregularity of the cornea,” Dr. Devgan said. Dr. Devgan thinks toric lenses work best for corneas with perfectly symmetric, regular astigmatism because the toric has perfectly symmetric optics. In eyes with asymmetric astigmatism—seen as a somewhat lopsided bowtie on topography—the advantage of LRIs is surgeons can do a more aggressive treatment at the meridian with the most astigmatism and less treatment on the side with less astigmatism, he said. Corneal elasticity changes with age, so LRIs are not as effective in younger patients, Dr. Devgan added. He avoids treating patients under 50 with LRIs, he said. Corneal pachymetry must also be taken into account; thicker corneas will require deeper cuts. “The best AK/LRI nomograms are the ones that are both age- and pachymetry-adjusted,” he said. Dr. Hamilton treats more than 1 D of astigmatism with toric IOLs, but if a patient wants a multifocal IOL, he’ll use an LRI and treat up to 1.5 D of astigmatism. If a patient has more than 2 D of astigmatism, he discourages multifocal use and prefers toric monovision for spectacle independence, he said. He also uses this option for post- refractive surgery patients. Dry eye is another consideration when choosing which option to use, as is prior corneal surgery, according to Dr. Hamilton. If a patient has had a corneal transplant, and the surgeon is worried the patient may need a second graft in the future, an LRI makes more sense because the orientation of a toric IOL would undoubtedly be off after a second transplant, he said. Laser versus manual LRIs When performing LRIs, surgeons have the option of making the incisions manually or using the femtosecond laser, and there are pros and cons to each method, according to the physicians. The femtosecond laser provides incomparable accuracy when it comes to depth and placement of incisions, but experienced surgeons get very good results with manual incisions as well. “Diamond blades can give equally good results in the hands of an expert surgeon,” Dr. Devgan said. One advantage of the femtosecond laser is it can measure pachymetry in real time and adjust the treatment so it is at exactly A toric IOL on postop day 1 Source: Uday Devgan, MD