Eyeworld

51 EW FEATURE © 2016 Stephens Instruments. All rights reserved. 800.354.7848 TOLL FREE IN THE USA | +1.859.259.4924 WORLD WIDE | stephensinst.com C E L E B R A T I N G 4 0 Y E A R S O F S E R V I C E T O T H E O P H T H A L M I C C O M M U N I T Y ISO 9001 ISO 13485 S9-2033 PRE- OPERATIVE ALIGNMENT MARKER For marking patient on gurney or at slit lamp prior to procedure Three fine marking points at 3, 6 and 9 o'clock for accurate reference Properly angled handled allows an unimposing approach to patient S9-2060 DEGREE GAUGE Intraoperative ring for aligning to steep axis and defining LRI points Large 11.7mm internal diameter provides for maximum visualization Crisp laser etched markings every 5° for greater marking accuracy S9-2065 TORIC IOL MARKER Works inside the degree gauge to mark prime meridian (steep axis) for LRIs and toric alignment Length of marks accommodates both limbal and corneal marking 4 0 Y E A R S O F Q U A L I T Y , S E R V I C E A N D V A L U E L I F E T I M E W A R R A N T Y Choose Stephens for better surgical outcomes. order aberrations in the cornea as a result of their surgery," Dr. Masket said. "If one adds a diffractive lens, this could contribute to higher order 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 compo- nents 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 focus- es 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 pres- byopic 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-re- fractive 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 some- times has a steep zone in the center, and an IOL with zero spherical aber- ration minimizes issues with precise alignment with the corneal steep zone, he said. Dr. Koch stressed caution when using toric lenses in eyes with pre- vious refractive surgery, requiring consistent biometry and topography readings, along with supporting astigmatic data from refraction. "Again, I find intraoperative ab- errometry to be valuable. I will sometimes implant toric IOLs in the post-RK eye, assuming again close alignment among biometric, topo- graphic, 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 accommo- dating lens becomes available. In post-LASIK eyes, if the LASIK or PRK correction was modest, physi- cians 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. EW Editors' note: Dr. Chang has financial interests with Abbott Medical Optics and Carl Zeiss Meditec (Jena, Germa- ny). 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

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