EyeWorld India June 2013 Issue

42 EWAP rEfrActivE June 2013 Views from Asia-Pacific Patrick VERSACE, MD Vision Eye Institute 2/75 Grafton ST Bondi Junction 2022, Australia Tel. no. +61-2-93863666 patrick.versace@bigpond.com A ccurate biometry has never been more important. With the progress of optical design, material science and surgical technique, modern IOLs offer solutions for most patients. We routinely use lenses that remain optically transparent without glistenings 1 , insert through 2-mm incisions, and correct all vision limiting optical parameters with correction of astigmatism, spherical aberration and presbyopia with bifocal and trifocal multifocal elements. More complex optical design makes an emmetropic outcome essential. A multifocal IOL will perform worse than a monofocal IOL in the presence of astigmatism. Various publications demonstrate that >1 D of astigmatism will cause vision with a multifocal IOL to be significantly impaired and be worse than a monofocal IOL. 2 It is also suggested that with refractive multifocal IOLs the presence of >1 D astigmatism may be associated with increased haloes. The presence of refractive error after multifocal IOL implantation is one of the strongest correlates with patient dissatisfaction. 3 We see this in clinical practice and it is vital to be able to address the unexpected refractive outcome. Dr. Epitropoulos has elegantly demonstrated the accuracy and predictability of the Zeiss IOL master as the gold standard in axial length measurement. Despite our ability to accurately measure axial length and keratometry, outliers will occur. Sometimes keratometry takes extra thought and it is useful to have access to topography in cases where the keratometry doesn’t make sense. For the majority of cases IOLMaster biometry is all that is needed for IOL power calculation and toric lens preparation. Accurate toric lens power calculation requires an algorithm that considers ACD, lens power, and pachymetry. Not all manufacturers include these parameters. Some nomograms simply take a spherical equivalent value and approximate a cylindric power from the corneal plane to the IOL plane. This will not always be accurate. 4 We need to have a robust plan B for dealing with refractive surprises. Refractive surprise does not need to be dramatic to require intervention. As little as 0.75 D sphere or cyl may cause a patient’s satisfaction to be reduced and require correction. Our secondary intervention rate after premium IOL implantation is less than 5% but for that 5%, retreatment can be like magic. PRK for the small refractive errors involved is effective. Rarely is IOL rotation for induced astigmatism (resulting from axis misalignment) required. Occasionally, a secondary/piggyback IOL helps a patient with an “inoperable” cornea. Patients in this era of lens implant surgery benefit from the coming together of accurate biometry, controlled surgery facilitating predictable refractive outcomes and new lens designs giving a full range of spectacle independent vision. References 1. Colin J, et al. Incidence of glistenings with the latest generation of yellow-tinted hydrophobic acrylic intraocular lenses. J Cataract Refract Surg . 2012;38(7): 1140-6. 2. Hayashi K, et al. Effect of astigmatism on visual acuity in eyes with a diffractive multifocal intraocular lens. J Cataract Refract Surg. 2010;36(8):1323-9. 3. Chiam PJ, et al. ReSTOR intraocular lens implantation in cataract surgery: quality of vision. J Cataract Refract Surg. 2006;32(9):1459-63. 4. Goggin M, Moore S, and Esterman A. Outcome of toric intraocular lens implantation after adjusting for anterior cham- ber depth and intraocular lens sphere equivalent power effects. Arch Ophthalmol. 2011;129(8):998-1003.Editors’ note: Prof. Chan has no financial interests related to his comments. Editors’ note: Dr. Versace is a consultant for Carl Zeiss Meditec but has no financial interests related to his comments. “We opted to use the immersion ultrasound value for the IOL calculations recommending a 26.5 D implant targeting a plano goal,” she said. “At one month the patient had a manifest refraction of –0.25 +0.50 x95.” The Lenstar’s recommendation was a 28.5 D IOL, “which would have resulted in a –2.00 myopic surprise,” she said. Dr. Epitropoulos believes the disparity between the two biometer readings “is likely due to different mathematical approaches used by the two devices in generating the measurements,” she said. “The IOLMaster 500 forms a composite based on software that automatically excludes inaccurate readings (digital signal processing), and the Lenstar device uses an arithmetic mean of measurements and includes outlier readings in its calculations.” The Lenstar and IOLMaster are “both major advances over what we’ve had in the past, and they help us get to our refractive target. Both devices are efficient and easy to use, but we still find that multiple measurements are often needed to achieve the best outcomes,” she said. As Wolfgang Haigis, MD, once said, “Trust automatic measurements only after having made sure they can be trusted.” Dr. Epitropoulos said, “In reality, we should always double check our measurements and make sure they make sense. There is still room for improvement in biometry, and as we get better at estimating effective lens position and developing intraoperative aberrometry, our final outcomes will become even more precise.” EWAP Editors’ note: Dr. Epitropoulos is a consultant for Carl Zeiss Meditec, but has no personal financial interests related to her comments. contact information Epitropoulos : aepitrop@columbus.rr.com Unexpected - from page 41