EyeWorld Asia-Pacific March 2017 Issue

EWAP FEATURE 15 March 2017 aberrations.” When considering a presbyopic lens in these patients, Dr. Masket said they should have a low degree of higher order aberrations, larger optical treatment zones, and relatively small pupils. From an optics and aberrations standpoint, the two main components are spherical aberration and chromatic aberration, Dr. Chang said. Spherical aberration is affected by refractive surgery. “To maximize visual image quality, you want to compensate for the corneal spherical aberration with the IOL,” he said. In post-myopic LASIK with high positive spherical aberration, you want to use a minus spherical aberration IOL, he said, such as the Tecnis. On the other hand, with post-hyperopic LASIK, you want a positive spherical aberration IOL. The other component that should be considered is chromatic aberration, Dr. Chang said, which is how well the optical material focuses the different wavelengths of light together. In general, the higher the index of refraction, the worse the chromatic aberration properties will be, so physicians should consider this in the IOL choice. Chromatic aberration doesn’t change with refractive surgery, he said. It will still be there, but in the presence of additional higher order aberrations, it becomes even more important to minimize it. Another exciting area is presbyopic IOLs. It’s hard to achieve plano on a post-refractive patient, particularly when you still have to worry about a lens that’s less tolerant to other aberrations, Dr. Chang said. This makes post-refractive IOLs a challenge, and these patients have paid money to get out of glasses. The Tecnis Symfony lens (Abbott Medical Optics) is an exciting new option, he said. Instead of two points of focus, it provides an extended depth of focus. Even if it’s a post-hyperopic LASIK patient, the continuous range of quality vision may provide more benefit than the potential benefit you’d lose from negative spherical aberration. With an extended range of vision lens, if any portion of that range hits plano, patients should have good uncorrected distance visual acuity, perhaps even in the presence of surface fluctuations, Dr. Chang said. But the challenge is to maintain good distance vision while providing them with good near vision as well. After RK, Dr. Koch suggested sticking to IOLs that have a lot of negative spherical aberration, like the Tecnis or Alcon aspheric lenses. An RK patient has a large amount of positive corneal spherical aberration, so it’s important to try to partially counteract this, Dr. Koch said. He suggested a similar strategy for post-myopic LASIK/PRK patients. Meanwhile, for patients who have undergone hyperopic LASIK, Dr. Koch prefers to use a lens with no spherical aberration. The post- hyperopic LASIK cornea sometimes has a steep zone in the center, and an IOL with zero spherical aberration minimizes issues with precise alignment with the corneal steep zone, he said. Dr. Koch stressed caution when using toric lenses in eyes with previous refractive surgery, requiring consistent biometry and topography readings, along with supporting astigmatic data from refraction. “Again, I find intraoperative aberrometry to be valuable. I will sometimes implant toric IOLs in the post-RK eye, assuming again close alignment among biometric, topographic, and refractive data, and the presence of a fairly uniform central 4-mm zone.” Meanwhile, presbyopic IOLs could be a potentially valuable option as well, but Dr. Koch said that he currently avoids them in RK patients until a true accommodating lens becomes available. In post-LASIK eyes, if the LASIK or PRK correction was modest, physicians could use an extended depth of focus or multifocal if the cornea looks very regular. The Symfony or ReSTOR 2.5 D (Alcon) lens are designed to preserve quality of vision, Dr. Koch said, and might be a reasonable match for corneas that are not severely aberrated. EWAP Editors’ note: Dr. Chang has financial interests with Abbott Medical Optics and Carl Zeiss Meditec (Jena, Germany). Dr. Koch has financial interests with Alcon, Abbott Medical Optics, and Clarity Medical Systems (Pleasanton, California). Dr. Masket has financial interests with Haag-Streit (Koniz, Switzerland). Contact information Chang: dchang@empireeyeandlaser.com Koch: dkoch@bcm.edu Masket: sammasket@aol.com the statistical bootstrapping technique on the data.” He also noted, “The results in long and short eyes are exactly opposite of that found in the 8,108-eye UK study 3 using optical biometry, which showed the Hoffer Q to be statistically more accurate in short eyes and the SRK/T in very long eyes, as I first recommended in 1993.” When it comes to preferred formulas, Dr. Hoffer said he would choose the Haigis formula with triple optimization, the Haigis-L for post-refractive eyes, and the new Hoffer H-5, especially in multi-racial groups. Dr. Holladay reiterated that he considers the Barrett Universal II, Olsen 2, and the Holladay 2 to be the best. EWAP References 1. Simon SS, et al. Achieving target refraction after cataract surgery. Ophthalmology . 2014;121:440–444. 2. Kane JX, et al. Intraocular lens power formula accuracy: Comparison of 7 formulas. J Cataract Refract Surg . 2016;42:1490–1500. 3. Aristodemou P, et al. Formula choice: Hoffer Q, Holladay 1, or SRK/T and refractive outcomes in 8108 eyes after cataract surgery with biometry by partial coherence interferometry. J Cataract Refract Surg . 2011;37:63–71. Editors’ note: Dr. Holladay has financial interests with Abbott Medical Optics (Abbott Park, Illinois), AcuFocus (Irvine, California), Alcon (Fort Worth, Texas), ArcScan (Golden, Colorado), Carl Zeiss Meditec, Oculus (Arlington, Washington), and Visiometrics (Barcelona, Spain). Dr. Hoffer licenses the registered trademark name Hoffer to all biometer manufacturers to assure proper programming of the Hoffer Q and Hoffer H-5 formulas. Contact information Hoffer: KHofferMD@aol.com Holladay: holladay@docholladay.com Perfecting IOL - from page 11