Eyeworld

APR 2017

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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EW NEWS & OPINION 40 April 2017 Selection of emmetropia is very likely to result in one meridian of correction being hyperopic. When selecting simple myopic astigma- tism, one meridian being dead plano means there is a still a significant chance for having to correct some hyperopia, albeit less than with the emmetropia/mixed astigmatism choice. If one chooses to target com- pound myopic astigmatism, similar to choosing a myopic outcome to avoid a hyperopic outcome, choos- ing to have all meridians myopic reduces the likelihood of needing to face treatment of a hyperopic meridian, a desirable goal perhaps since most agree hyperopic treat- ments are less desirable than myopic treatments. My own practice is to target between –0.50 and –1.00 in the least myopic meridian, perhaps some more in cases of a greater anticipat- ed spread of results such as prior LASIK or corneal disease. In the next installment, we will explore the deliberate use of residual astigmatism to improve depth of focus and near uncorrected vision as well as strategies for the patient who has significant refractive error but a significant surgical cataract in only one eye. EW Editors' note: Dr. Gossman is in private clinical practice at Eye Associates of Central Minnesota, St. Cloud, Minneso- ta. He has no financial interests related to this article. Contact information Gossman: n1149x@gmail.com by Mitchell Gossman, MD Pulse of ophthalmology: Survey of clinical practices and opinion press time we had one toric multifo- cal IOL available in the United States currently, the Symfony Toric (for- merly Abbott Medical Optics [AMO], now Johnson & Johnson Vision [J&J, Santa Ana, California]), but not the others yet that are available outside the U.S. How do you correct resid- ual astigmatism? Suppose you have more astigmatism you are comfort- able treating with a limbal relaxing incision (LRI), or you are opposed to them and you wish to treat with laser vision correction such as PRK or LASIK afterward? What refractive error do you target to facilitate this? The seventh question was, "For a patient undergoing surgery with a spherical multifocal IOL who has corneal astigmatism of a degree that LRI is inadequate to correct astig- matism, you elect to do planned post-IOL laser vision correction such as LASIK or PRK. What category of refractive target do you select?" generally regarded as more favorable to laser vision correction if that is desired later. A greater uncertainty in refractive outcomes will result in more hyperopic errors. There is a temptation to target additional myopia in an effort to avoid hyper- opia, but this will result in a greater number of myopic errors. So, what are we doing? The responses were: Most do, in fact, opt to target more myopia than normal in these situations even at the risk of even more myopia. But by how much? The sixth question was, "Follow up from #5. Acknowledging that no case is 'typical' and the answer depends on the specifics for the case at hand, how much myopia do you target as a hedge against a hyperopic result, above and beyond your nor- mal method such as targeting 'least minus'?" What about the patient where you know for a fact there will be residual refractive error, does that influence your decision on what refractive error to target? Take spe- cifically the case of the patient with astigmatism. What if you propose to use a multifocal IOL in a patient with corneal astigmatism? Yes, at The third in a series on the complexities of everyday IOL decisions T his is Part 3, a continuation of our exploration of the subtleties of IOL power selection in various clinical scenarios. This is derived from a survey of 74 ophthalmolo- gists who volunteered to participate from the ranks of participants of the EyeConnect online community and volunteers in North America. Re- sponses are anonymous to encour- age candor. Totals may differ from 100% due to rounding. In follow up of the issue of avoiding a hyperopic result when targeting emmetropia, we will explore those cases where it seems more difficult to accomplish this. The fifth question was, "For a case with known challenges in IOL power determination, such as prior LASIK, basement membrane dystro- phy, staphyloma, etc., do you delib- erately target additional myopia as a hedge to avoid a hyperopic result?" Anything that causes more uncertainty in biometry compo- nents, especially keratometry and axial length, will add additional uncertainty to the accuracy of the refractive targeting. An error on the myopic side, while it compromises the good uncorrected distance acuity you and the patient desired to the same degree as a hyperopic error, at least it provides uncorrected focus at some distance. Also, myopia is Art of intraocular lens power selection, part 3 Yes 82% No 18% –0.25 27% –0.50 47% –0.75 15% –1.00 5% Other (one responded –1.50) 1% Emmetropia, and plan correction of mixed astigmatism 31% Simple myopic astigmatism, i.e., one meridian at plano and the others myopic, e.g., plano –3.00 x 90 (in plus cylinder –3.00 +3.00 x 180) 32% Compound myopic astigmatism, i.e., one meridian at myopia and the others more myopia, e.g., –1.50 –3.00 x 90 (in plus cylinder –4.50 +3.00 x 180) 24% Mitchell Gossman, MD Other (several commented on avoiding laser vision enhancements entirely) 13%

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