Trifocal lenses

Reducing the intermediate range dip in visual acuity (VA) while maintaining near vision adequate for reading in most patients gives trifocal intraocular lenses (IOLs) an advantage over bifocal or extended-depth-of-focus designs, Thomas Kohnen MD, PhD, FEBO told the 2016 ASCRS•ASOA Symposium & Congress in New Orleans, USA. Patients also experience less glare and halos with trifocal IOLs than with bifocals, and trifocal dysphotopsias are about the same as with extended-depth-of-focus IOLs, added Dr Kohnen, who is Professor and Chair of the Department of Ophthalmology at Goethe University Frankfurt, Germany. “My choice now is quadrifocal, trifocal or extended-depth. I am not using bifocal lenses anymore,” he said. Spectacle independence gives trifocals – including Zeiss’ AT LISA tri, PhysIOL’s FineVision and Alcon’s AcrySof IQ PanOptix – an advantage over extended-depth-of-focus IOLs, such as Abbott Medical Optics’ Symfony lens, Dr Kohnen said. “Symfony patients need reading glasses most of the time, at least one dioptre addition, whereas most trifocal patients do not,” he noted. DEFOCUS CURVE IS KEY Defocus curves illustrate the trifocal IOL advantage, Dr Kohnen added. Ideally, the defocus curve would be flat at 0.0 logMAR or 20/20 from plano all the way through 3.0D defocus. With current diffractive bifocal IOLs with a 2.5D or 3.0D add, vision hits 0.0 logMAR or 20/20 at distance, then dips to about 0.2 logMAR or 20/35 at about -1.5D defocus, and rises back to about 0.1 logMAR or 20/25 at -2.5D to -3.0D. Trifocals generally reduce the intermediate dip, Dr Kohnen said. In a study he conducted with 54 patients implanted with the trifocal AT LISA tri 839MP, mean binocular VA was -0.1 ± 0.1 logMAR or about 20/16 at distance, and 0.0 ± 0.1 logMAR or 20/20 at intermediate and near distances. Moreover, contrast sensitivity was within normal range in photopic, mesopic and mesopic with glare conditions. Patients also reported some dysphotopsias, with halos the most common at 60 per cent, followed by glare at about 35 per cent. However, patients judged optical quality good, with a mean 7.3 of 10 in bright daylight, 7.4 in ambient light and 6.8 in dawn light, and were satisfied with vision for most activities. (Kohnen T et al. Am J Ophthalmol 2106;161:71-72) Other authors have reported similar results with other trifocal lenses, including the FineVision and PanOptix, Dr Kohnen said. “Trifocal IOLs give good VA at far, intermediate and near distance, and patient satisfaction is high despite some optical phenomenon… my patients are satisfied with these lenses.” Thomas Kohnen: kohnen@em.uni-frankfurt.de

Tags: glare, halos, visual acuity