Eyeworld

EW NEWS & OPINION January 2017 25 IOL power. To take a trivial example, consider a case where a +20.00 IOL is projected to produce +0.01 and a +20.50 IOL is projected to produce –0.35. In a case where you want target as close to dead emmetropia as possible, perhaps a multifocal IOL, you might consider this "least minus" target of −0.35 unacceptable and a result of +0.01 to be close enough. Where to draw the line? In Figure 1, if your cutoff is 0.10, you would skip the choice calling for +0.11 and instead select the least minus target of –0.25. If your cutoff is 0.15, you would accept the target +0.11. One respondent in this camp said +0.05. One said +0.10. Two said +0.15. One said +0.25. I employ this third method and will accept up to +0.09, but for +0.10 or more I will go for the least minus. Sometimes an inadvertent myopic result is a serendipitously pleasing one with the patient unex- pectedly discovering, and enjoying, the near focal plane. But suppose the refractive surprise is not a happy one for the patient, such as unwant- ed myopia or even hyperopia, and he or she wants surgery on the other eye. What then are we doing? The second question was, "You have performed surgery on the first eye, targeting emmetropia because the patient desires best distance un- corrected visual acuity, and instead a refractive surprise of –2.00 occurs. Assume this is a typical case without unusual features, i.e., your measure- ments are correct, remeasurement is satisfactory, the correct IOL was used, and clerical errors have been excluded, what adjustment, if any, do you make for the second eye? If you consider a –2.00 surprise beyond Consider again the case in Figure 1. When you select the IOL power closest to emmetropia, the ZCB00 IOL (Abbott Medical Optics, Abbott Park, Illinois) power +23.50 in this case, it is projected to result in a refractive error of +0.11. You are, with mathematical certainty with a sufficiently large number of cases, producing the most patients with the best distance uncorrected acuity with the +23.50 lens power. If you deviate from this and select the higher power IOL—+24.00 in this case—you now have a fore- cast refractive error of –0.25 rather than the other IOL with the small- er +0.11, and there will be more patients with a greater deviation (in absolute value) from emmetropia. The reason most of us do this is that we regard myopia as better than hyperopia. Hyperopia is usually the enemy. When, for example, there is a +1.00 refractive error, there is no useful focal plane for the patient to enjoy unaided clear visual acuity. When there is a –1.00 refractive result, while the distance acuity is compromised somewhat, similar in degree to the +1.00 result, at least the patient enjoys a focal plane of clear vision about 40 inches away for a computer. So the targeting of myopia acts as a hedge against a hy- peropic result. By hedging at −0.25, we acknowledge that we would rather reduce the number of +1.00 surprises and are willing to pay the price of an excess of –1.25 surprises. A compromise position is to target closest to emmetropia—with the caveat to accept no projected hy- peropic result greater than a certain number. If that number is exceeded, opt instead for the least minus myo- pic result with the next step higher Femto Dissectors 3360 Scherer Drive, Suite B, St. Petersburg, FL 33716 800-637-4346 • Tel: 727-209-2244 • Fax: 727-341-8123 Email: Info@RheinMedical.com • Website: www.RheinMedical.com 1 Developed In Coordination With Steven Dewey, M.D. 2 Developed In Coordination With Neil Friedman, M.D. 3 Developed In Coordination With Rolando Toyos, M.D, 4 Developed In Coordination With David Folden, M.D. Sarto/Girl with a petrarchino ACBG 1368 Rev.A Call 727-209-2244 For More Information. A) B) C) D) E) A) 08-07160 Dewey 1 Horizontal Femto Chopper. B) 08-07161 Friedman 2 Double-Ended Femto Incision Dissector. C) 08-14561 Toyos 3 Femto Dissector. D) 08-10143 Femtosecond Double- Ended Incision Dissector, 1mm & 2mm. E) 08-10144 Folden 4 Femto Double- Ended Dissector, 0.7mm & 1.2mm. continued on page 26 No adjustment 12% Full adjustment, i.e., target +2.00 9% Partial adjustment of 50%, i.e., target +1.00 70% Other percentage (two selected a 75% adjustment, others described different strategies) 8% Table 2: Results of question 2

• Cover