Eyeworld

APRIL 2019 | EYEWORLD | 85 R eye dominance and provide better stereoacuity," he said. "Monovision has no extra cost, however. The decision is delayed for the second eye, and it can be simulated with contact lenses prior to surgery. Monovision is reversible, not only by lens exchange, but with the use of bioptics, add-on lenses, contact lenses, or glasses." Pearls Dr. Assia advises patients with good vision on all the options. "If the patient desires to be spectacle independent, my first choice would be trifocal lenses. With astigmatism in excess of 0.75 D, es- pecially if it is against the rule, it must be correct- ed. We do expect to have some photic phenome- na with trifocals, but usually it improves with time and rarely interferes clinically," he said. "If the patient needs good intermediate vi- sion, an EDOF or low monovision, about 1.0 D, both work well. But if the patient does not desire or cannot afford multifocal lenses, I would choose to target the first eye for emmetropia and aim for distance, regardless of which eye is dominant. If vision is good, I would recommend monovision for the second eye between 1.5 and 2.0 D, typi- cally 1.75, even if the patient did not ask for near vision correction," he said. Monovision and multifocal IOLs have their drawbacks, despite reports of high patient satisfaction in both categories. Stereoacuity is decreased by monovision because one eye is set for distance and the other for near. Multifocal lenses, on the other hand, are associated with photic phenomena, like halos, glare, and difficul- ties in night driving. In most studies, multifocal lenses achieved better spectacle independence, somewhere between 65 and 95%, according to Dr. Assia, while this rate is lower for monovision, achieving between 35 and 90% spectacle freedom. Choosing "When deciding on multifocal correction, the de- cision must be made before the first operation— we do either both eyes or neither of the eyes. Monovision is often times a decision made on the second operation. If the distance vision is good after the first operation, we can do the second eye for near. If the patient is not happy after the first operation, we do the second eye for distance, for example, and this patient would use reading glasses," Dr. Assia said. The decision comes down to the visual preferences of the individual patient. "If the patient wants to cover all distances or the patient's occupation requires good binocularity, multifocals are probably superior. They are independent of acuity, Dr. Reinstein reported. There was also no change in contrast sensitivity. Investigators think that this does not arise from the same source as traditional DLK. "Our leading theory at the moment lies in how the interface differs between LASIK and SMILE," Dr. Reinstein said. With SMILE, energy from the femtosecond laser causes microscopic divots in the stromal tissue when creating an interface; in LASIK, performing an excimer laser ablation es- sentially smooths the stromal bed. "In SMILE, no excimer laser is needed, so no additional smooth- ing takes place," Dr. Reinstein said. "One idea may be that the inflammatory cells tend to clump into the divots rather than racing across a smooth ablated interface." When performing SMILE, Dr. Reinstein ad- vises practitioners to keep the possibility of sterile multifocal inflammatory keratitis occurring post- operatively in mind. "Our take-home message is that these eyes must be followed very closely," he said. Localized stromal melting may be more like- ly due to the focal nature of this condition. With this in mind, practitioners may want to perform an interface washout earlier than with the classic appearance of DLK, Dr. Reinstein recommended. In addition, these cases should be followed closely because it is important to rule out an infectious component if there is any doubt about the origin, he concluded. continued from page 83

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