EyeWorld India June 2019 Issue

EWAP JUNE 2019 63 FEATURE by Michelle Stephenson EyeWorld Contributing Writer Trifocal IOLs provide near, intermediate, and distance vision Although not yet approved for use in the United States, trifocal IOLs are providing near, intermediate, and distance vision to patients in Europe and Canada Editors’ note: Dr. Berdahl has ƂPCPEKCN KPVGTGUVU YKVJ #NEQP Johnson & Johnson Vision (Santa #PC %CNKHQTPKC 4Z5KIJV #NKUQ 8KGLQ %CNKHQTPKC CPF $CWUEJ .QOD $TKFIGYCVGT 0GY ,GTUG[ &T 6JQORUQP JCU ƂPCPEKCN KPVGTGUVU YKVJ #NEQP ,QJPUQP ,QJPUQP CPF %CTN <GKUU /GFKVGE &T 0GWJCPP JCU PQ ƂPCPEKCN KPVGTGUVU TGNCVGF VQ JKU EQOOGPVU Contact information Berdahl: john.berdahl@vancethompsonvision.com Neuhann: prof@neuhann.de Thompson: vance.thompson @vancethompsonvision.com B ecause multifocal IOLs do not provide optimal intermediate vision, surgeons often mix and match IOLs to achieve the best vision at all three distances. “We will either implant an extended depth of focus (EDOF) IOL or a lower add multifocal in the dominant eye, and we will implant a higher add bifocal in the non-dominant eye in an attempt to get all three distances,” said Vance Thompson, MD , Sioux Falls, South Dakota. In contrast, trifocals can be implanted in both eyes because they provide vision at all three distances. Three trifocal IOLs are currently approved for use outside of the United States: the AT LISA (Carl Zeiss Meditec, Jena, Germany), the AcrySof IQ PanOptix (Alcon, Fort Worth, Texas), and the FineVision (PhysIOL, Liège, Belgium). According to Thomas Neuhann, MD , Munich, Germany, the basic principle of two diffractive step-widths combined to provide distance, intermediate, and near foci is used by all of these lenses. “The Alcon lens uses a particular diffractive construction to obtain an intermediate range from 1.2 to 0.6 m. The intermediate focus is not created at the expense of the light distributed to the distance and near foci but makes light otherwise lost, such as in bifocal diffractive lenses, available and usable for the intermediate focus,” he explained. John Berdahl, MD , Sioux Falls, South Dakota, noted that the adoption rate of trifocals outside of the United States has been tremendous. “In many places, it’s the go-to lens type. It is about defocus curves and trying to provide as much of a continuous range of vision as possible, while avoiding unwanted side effects like positive dysphotopsias,” he said. Advantages and disadvantages The advantage of trifocal IOLs is that they provide vision at all three distances. “No currently available single lens provides distance, intermediate, and near vision,” Dr. Berdahl said. “Trifocals would give each eye the ability to see well at all three distances, which I suspect will allow for more forgiveness if we aren’t exactly on target.” “Because all multifocal IOLs divide the incoming light into more than one focus, the effect of the light in ‘out of focus’ images reduces the contrast of ‘in focus’ images,” Dr. Thompson said. “If a patient is looking at a distance, he or she will have near and intermediate images that are not in focus, which can reduce contrast sensitivity and modulation transfer function (MTF). MTF is a useful optics measure of true or effective resolution, since it accounts for the amount of blur and contrast over a range of spatial frequencies. As a result, unwanted visual phenomena, including glare and halo, can occur. One of the main reasons that multifocal IOLs are being implanted with growing frequency is because the optics have been optimized to the point that patient satisfaction is much higher than multifocal implants of 10 or 20 years ago. There is a much lower incidence of glare and halos. Twenty years ago, they were 0.1% of the implants I placed, and now multifocals are 40% of the implants that I use because of how happy they make my patients who desire to be spectacle independent. I have been in trifocal FDA trials in the United States, and I think they’re going to be a game-changer for us, too.” However, there are certain patients for whom Dr. Thompson would be cautious about recommending any implant that splits light, whether it is an EDOF or multifocal lens. Any eye pathology that scatters light in an unsophisticated way can degrade the sophisticated optics of modern-day multifocals or EDOF lenses. “For example, dry eye, epithelial basement membrane dystrophy, or a corneal irregularity, such as keratoconus, should be treated before implantation of a trifocal. If we cannot decrease the higher order aberration state of the cornea and tear w“ ̜ >˜ >VVi«Ì>Li iÛi] Üi don’t want to add a multifocal implant to that optical system. We also like to make sure the 6JKU CTVKENG QTKIKPCNN[ CRRGCTGF KP VJG ,CPWCT[ KUUWG QH EyeWorld . It has DGGP UNKIJVN[ OQFKƂGF CPF CRRGCTU JGTG YKVJ RGTOKUUKQP HTQO VJG #5%45 1RJVJCNOKE 5GTXKEGU %QTR D VICES