June 2016

 

COVER FEATURE

 

Controversies in ophthalmology

Limbal relaxing incisions versus toric IOLs for astigmatism correction


by Lauren Lipuma EyeWorld Contributing Writer

 
 

Patients will be seeing the world through our surgeries every waking moment for the rest of their lives.

My goal is to give the very best to the patient and to place cost as a secondary consideration. Uday Devgan, MD

 
toric IOL

A toric IOL on postop day 1 Source: Uday Devgan, MD

Surgeons discuss the pros and cons of each treatment

Ophthalmologists have 2 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 astigmatismaround 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 correctionsfrom 1 to 4 Dthe 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 astigmatismseen as a somewhat lopsided bowtie on topographythe 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, hell 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 the right depth, Dr. Devgan said. In addition, laser treatments are initially closed and can be opened in a step-wise manner to titrate the astigmatic effect. Dr. Devgans surgery center has both the LenSx (Alcon, Fort Worth, Texas) and Catalys (Abbott Medical Optics, Abbott Park, Illinois) femtosecond laser systems. I use a Victus laser [Bausch + Lomb, Bridgewater, New Jersey], which gives me real-time OCT, and that allows me to keep my incisions deep without risking perforation, Dr. Whitman said. The cost of the laser, however, must be factored in when making a surgical decision. We must remember that the femtosecond laser is very expensive to purchase and use: approximately $500,000 initial cost, then $50,000/year maintenance contract, and then hundreds of dollars in additional fees per eye, Dr. Devgan said. Dr. Hamilton prefers to make incisions with the laser for 3 reasons: He finds the laser is more predictable and can treat higher levels of astigmatism more accurately than with a blade, he can titrate the effect by leaving the incisions closed and opening them after the postop refraction, and the laser does not create an epithelial defect like the diamond blade does, so there is minimal postop discomfort, he said.

Outcomes and cost to the patient

Toric IOL article summaryGiven all of these considerations, how do refractive outcomes compare between LRIs and toric IOLs? I give torics the winning mark as the results will generally remain stable over time, Dr. Whitman said. That is why knowing that your manual or femto incisions are deep enough is critical, as the result may lessen over time if the incisions are shallow. Dr. Devgan finds that at 1.25 D of astigmatism or less, the results for each procedure are essentially the same and patient satisfaction is equally high. At the 1 D range, the 2 techniques yield similar outcomes, according to Dr. Hamilton, but the outcomes depend on how regular the astigmatism is. Fortunately, as the amount of astigmatism increases, it typically becomes more regular, he said. At 1 D, the astigmatism is often a bit irregular, which detracts from the toric [IOL] efficacy, he added. When comparing efficacy at the 1 D level, this factor counterbalances the lack of predictability of the [LRI]. Because neither treatment is covered by insurance, cost can be an issue for some patients. If a surgeon can treat the astigmatism and give the patient great vision without the need for glasses, the cost savings over a few years will certainly favor paying for the best surgical results, according to Dr. Devgan. Patients will be seeing the world through our surgeries every waking moment for the rest of their lives, he said. My goal is to give the very best to the patient and to place cost as a secondary consideration. For the few patients who dont heal as predicted and dont quite hit the intended refractive target, his practice offers a complimentary laser vision correction to give them the best possible outcome.

Editors note: Dr. Devgan has financial interests with Abbott Medical Optics and Bausch + Lomb. Dr. Hamilton and Dr. Whitman have no financial interests related to their comments.

Contact information

Devgan
: devgan@gmail.com
Hamilton: hamilton@jsei.ucla.edu
Whitman: whitman@keywhitman.com

Limbal relaxing incisions versus toric IOLs for astigmatism correction Limbal relaxing incisions versus toric IOLs for astigmatism correction
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