Eyeworld

77 EW FEATURE October 2018 • Revisiting astigmatism can also achieve values such as this for residual refractive astigmatism." Most of the time, Dr. Koch does not think that intraoperative aberrometry improves the accuracy of toric IOL selection and alignment. "For posterior corneal astigmatism in particular, its magnitude in a nor- mal eye may be below the threshold of noise for intraoperative aberrom- etry so I am not sure that it adds more at this point than our current nomograms," he said. It is important not to insert values for total corneal astigmatism into toric IOL calculators that use anterior corneal measurements to estimate posterior corneal astigma- tism. "If a measuring device provides a true, or net, corneal power, the posterior cornea has already been incorporated into this value," Dr. Hill said. "Adding a posterior corne- al algorithm would account for the posterior cornea a second time and make the calculation inaccurate." "If you have against-the-rule astigmatism, the posterior cornea often doesn't contribute a lot, typi- cally around 0.2 D," Dr. Koch said. "But you have to add in lens tilt. Postoperative IOL tilt (which can be predicted from preoperative crys- talline lens tilt 1,2 ) introduces up to 0.2 D of additional against-the-rule refractive astigmatism. 3 " Measurements will continue to improve and evolve, including the impact of lens tilt, Dr. Koch predict- ed. "In the future, our preoperative measurements will include total cor- neal astigmatism and crystalline lens tilt. Knowing the latter and the type of IOL and its meridional alignment, we will be able to predict the refrac- tive impact of IOL tilt. These steps will take us to a new level of accu- racy in optimizing our treatment of patients' astigmatism," he said. EW References 1. Hirnschall N, et al. Prediction of postoper- ative intraocular lens tilt using swept-source optical coherence tomography. J Cataract Refract Surg. 2017;43:732–736. 2. Wang L, et al. Evaluation of crystalline lens and intraocular lens tilt using a swept-source optical coherence tomography biometer. J Cat- aract Refract Surg. Accepted for publication. 3. Weikert MP, et al. Astigmatism induced by intraocular lens tilt evaluated via ray tracing. J Cataract Refract Surg. 2018; 44:745–749. Editors' note: Dr. Hill has financial interests with Alcon (Fort Worth, Texas) and Haag-Streit. Dr. Koch has financial interests with Alcon, Johnson & Johnson Vision (Santa Ana, Califor- nia), and Carl Zeiss Meditec. Contact information Hill: hill@doctor-hill.com Koch: dkoch@bcm.edu (800) 367-8327 DuPont, WA 98327 info@lacrimedics.com • www.lacrimedics.com ©2018 Lacrimedics, Inc. 1 ASCRS Clinical Survey 2015. Global Trends in Ophthalmology and the American Society of Cataract and Refractive Surgery. Don't let 41% of your patients with OSD go untreated, especially when they need something more than artificial tears. Lacrimedics' VisiPlug® is FDA approved for the treatment of the Dry Eye components of varying Ocular Surface Diseases (OSD) and after surgery to prevent complications due to Dry Eye Disease. VisiPlug® - Provides approximately 180 days of occlusion so you can better manage your patient's treatment plan. 41% of refractive or cataract surgery patients have ocular surface dysfunction levels requiring some treatment beyond artificial tears! 1 0.4mm 0.5mm See you at AAO in Booth #2758

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