EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/111385
56 EW FEATURE February 2011 Refractive/astigmatism February 2013 Experts continued from page 55 made in what location, patients drift in the direction of against-the-rule with age. ���The other possibility is that when you put an implant in, that implant is never parallel or perpendicular to the visual axis; it may be tilted a little bit and that tilt induces a small amount of astigmatism. That���s under investigation right now. In other words, that���s [Dr. Koch���s] observation, but there���s no mechanism yet that���s been confirming that that observation may be correct. The reason for that observation is still up in the air,��� Dr. Holladay said. Against-the-rule astigmatism According to Dr. Koch, against-therule astigmatism cases need more adjustment than with-the-rule cases because the posterior cornea ���increases the amount of against-therule astigmatism.��� ���So in using a toric IOL, you want to go up at least one half D of increased correction for the againstthe-rule patient, and in terms of relaxing incisions for the againstthe-rule patient, yes, they are more likely to need it, even if there���s a small amount of against-the-rule,��� he said. The power of one The The difficult part of against-therule astigmatism cases is that relaxing incisions must not be made too long, he said. If they are, they can create dryness and foreign body sensation because of incised corneal nerves. ���That astigmatism, in my mind, is more challenging to treat,��� Dr. Koch said. ���I more often will go to a toric lens and do a relaxing incision in those, whereas more often in with-the-rules, for amounts up to 1 D, I do nothing and will not use a 1 D toric IOL until anterior corneal with-the-rule astigmatism is 1.7 D.��� Dr. Holladay said in some cases, despite the best planning, the outcome is still not as desired. In those cases, his Holladay IOL Consultant has a Toric Back Calculator tab that provides physicians with a second chance. ���It allows the surgeon to take the observed axis of the lens and the refraction and by observed axis, you look in with the slit lamp, you line up the slit beam and you say, that lens is at 45 degrees. And then, if you refract the patient, with those two bits of information, I can calculate for you exactly how much you need to rotate that lens to the perfect position,��� he said. He also recommended that physicians look at the post-op refraction and observed axis or post-op refraction and K reading. ���When you do end up with an outcome that���s not on the button, you use that Toric Back Calculator to find out how much you need to rotate it to get it to the right position. That helps a lot, and it tells you what the residual astigmatism is,��� he said. EW Reference 1. Koch, D., Ali, S.F., Weikert, M.P., Shirayama, M., Jenkins, R., and Wang, L., Contribution of posterior corneal astigmatism to total corneal astigmatism. J Refract Surg. 2012: 38: 2080-2087 FE MTO PLATFORM AT THE ONE FEMTO PLATFORM for cornea, presbyopia for cornea, presbyopia and cataract. cataract. Presenting the unparalleled Ziemer FEMTO LDV Z Models ��� a technical revolution in ocular surgery. No laser is more precise, more powerful or more progressive when it comes to meeting all your procedural needs in a single platform. Ziemer���s With Ziemer���s FEMTO LDV Z Models, now you can operate with a modular femtosecond system that is easy to configure, designed to grow with your practice ��� cornea and presbyopia today, cataract tomorrow. tomorrow. www.ziemergroup.com www.ziemergroup.com Editors��� note: Dr. Hill has financial interests with Alcon (Fort Worth, Texas). Dr. Holladay is the developer of the Holladay IOL Consultant programs. Dr. Koch has financial interests with Alcon, Abbott Medical Optics (Santa Ana, Calif.), OptiMedica (Sunnyvale, Calif.), and Ziemer. Contact information Hill: 480-981-6111, hill@doctor-hill.com Holladay: holladay@docholladay.com Koch: 713-798-6443, dkoch@bcm.tmc.edu The Ziemer FEMTO LDV Z Models are FDA cleared and CE marked and available for immediate delivery. For some countries, availability may be restricted due to local regulatory requirements; please contact Ziemer for details. The creation of a corneal pocket is availability manufacturers part of a presbyopia intervention. Availability of related corneal inlays and implants according to policy of the individual manufacturers and regulatory status in the individual countries. Cataract procedures with the FEMTO LDV Z2, Z4 and Z6 models are not cleared in the United States and in all other countries. An upgrade possibility for these devices is planned once cataract options are available and cleared by the responsible regulatory bodies.