Eyeworld

EW FEATURE 31 Likewise, as little as 0.5 D of residual sphere can increase patient dissatisfaction with multifocal lenses, Dr. Schallhorn said. "Espe- cially for a multifocal lens, the dis- tance vision needs to be fine-tuned within a very tight refractive range," he said. John Berdahl, MD, assistant professor of ophthalmology, Univer- sity of South Dakota, and in practice at Vance Thompson Vision, Sioux Falls, S.D., agreed that there is little room for error in these patients. "For multifocal IOLs, they're the least tolerant to residual refractive error, so patients generally need to be within at least 0.5 D of sphere and between 0.5 and 0.75 D of cylinder in order to be happy," he said. Dr. Berdahl finds that patients with accommodating IOLs tend to be more forgiving of residual error. "Accommodative lenses by defini- tion are going to have a more variable effective lens position, so it's a bit harder to hit the spherical target," he said. "The good thing is they're more forgiving because they're going to accommodate through some of that refractive error." A little myopic error will enable them to read more easily, Dr. Berdahl said. He estimated that accommodative lens patients can tolerate about 0.75 D of cylinder and be satisfied. "Still, removing that cylinder would certainly improve their quality of vision," he said. The fact is, the more astigma- tism patients have preop, the greater the chance that they are going to need some sort of enhancement postop, Dr. Berdahl said. Also, depending on the IOL type, patients may not be able to tolerate as much error. He has found that with multi- focal IOLs, the residual astigmatism tends to be bothersome, whereas with accommodating lenses, missing the spherical target tends to be the issue. A patient's expectations can also factor in. "I don't ever promise that I'm going to get someone out of their glasses for any and all activities," Dr. Berdahl said. Nonetheless, given how much patients are spending on these lenses, he emphasized that patients should be hopeful about more func- tionality in their lives and greater freedom from spectacles. "Once that pact is made between the surgeon and the patient, the surgeon has a responsibility to do everything that he can to make that patient as happy as possible with the vision," Dr. Berdahl said. Scott M. MacRae, MD, professor of ophthalmology and visual science, University of Rochester, Rochester, N.Y., has found that about 20% of patients need an enhancement. In his experience, enhancements are slightly more common in high myopes, hyperopes, and in post- refractive eyes because these are harder to predictably treat. Dr. MacRae also has found that for astigmatism refinement, other factors besides residual amount may play a role. For example, those with large pupils may be more sensitive to astigmatism, he said. "A 6 mm pupil is about twice as sensitive, with about twice as much image quality reduction as with a 3 mm pupil," Dr. MacRae said. Also, the orientation of the astigmatism is important. "The brain is tuned to vertical and horizontal lines," he explained. "There will be about a 50% reduction in image quality if the astigmatism is oblique because the brain isn't tuned to looking at oblique patterns as keenly as it is to horizontal and vertical patterns." To determine if any enhance- ment is needed, he places the correc- tion in a pair of trial lenses and asks patients whether this improves their vision, while they are in the exam lane. "If they notice that it improves their vision, I'll go ahead and treat; if they don't notice significant improvement, I recommend not treating," he said. Dr. MacRae thinks that refrac- tive premium lens treatment is evolving and that surgeons are becoming more attuned to the fact that they need to do enhancements to optimize vision. "I look at doing premium lenses as entering into a contract with patients, telling them that I'm going to try to get them the very best vision that they can achieve without putting them in harm's way," Dr. MacRae said. "For premium surgeons to be successful, they have to commit to that type of approach." July 2014 Keratorefractive enhancement of pseudophakes 6DQGHUVYLOOH5G/H[LQJWRQ.<86$ 3KRQH)D[ (0DLOVWHSKHQVLQVW#DROFRP ZZZVWHSKHQVLQVWFRP Use These Instruments for a Discount on Ours stephensinst.com Enter Promo Code "SUMMER10" for a 10% Discount on Orders Placed on Our Website. Enhancement restrictions However, not all cataract practition- ers are in a position to correct residual refractive error, he said. "One of the problems with the premium lens practice is that most general cataract surgeons aren't equipped or psychologically ready continued on page 33 30-37 Feature_EW July 2014-dl_Layout 1 6/30/14 8:42 AM Page 31

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