IOL range expanding
New optical designs for presbyopic IOLs offer patients more options
The range of presbyopic IOLs continues to expand with new diffractive extended depth of focus (EDOF) optical designs and new hybrid and accommodating IOLs on the horizon, reports Jorge Alió MD, PhD, FEBO, Universidad Miguel Hernández, Alicante, Spain.
“New presbyopic IOLs present opportunities for the present and the future, but to use them properly we have to be aware of what they offer and how they fit our patients’ needs,” Prof Alió told the 37th Congress of the ESCRS in Paris, France.
Among multifocal IOLs there are new diffractive models that target the decrease in haloes and glare by decreasing the near optical power, substituting it by an EDOF effect. There are also new refractive multifocal IOLs with new optical profiles, and new materials.
WHAT IS EDOF?
Prof Alió noted that the EDOF IOL concept has become very popular, but there is some confusion about what constitutes an EDOF lens. EDOF IOLs manipulate the spherical aberration of the IOL in a way that elongates the defocus curve. That in turn eliminates the overlap of near and far images and therefore theoretically eliminates the halo effect.
“The trade-off is a decrease in the quality of the retinal image, which limits their performance as there is a degradation of the vision quality. This is why the near vision capability has to be limited to about one dioptre,” he added.
New EDOF IOLs include the Mini WELL (SIFI, Italy), which generates multifocality by having positive spherical aberration in the centre and negative spherical aberration in the mid-periphery. Employing an entirely different strategy for multifocality or extended depth of focus are new IOLs and implants that use the pinhole effect. One example is the IC-8 (AcuFocus) IOL, which has a 3.23mm opaque mask with 1.36mm aperture imbedded within the optic.
Another new idea is the XtraFocus Pinhole Implant (Morcher), designed for ciliary sulcus implantation as a piggyback lens. Composed of a black hydrophobic acrylic material, it has an overall diameter is 14mm and a 1.3mm central aperture. The implant’s material blocks visible light and is transparent to infrared light above 750nm, allowing retinal examination with optical coherence tomography and scanning laser ophthalmoscopy.
HYBRID MULTIFOCAL-EDOF IOLs
Prof Alió noted that some of the so-called EDOF lenses available today are really multifocal lenses with low near-add power. By manipulation of spherical aberration these lenses leave part of the light out of focus to avoid the overlapping of images and the consequent haloes and glare.
“EDOF lenses should be called such only when they do not have either refractive or diffractive added multifocality. If they do, they should be called hybrid multifocal-EDOF IOLS,” Prof Alió said.
Among multifocals of this type is the Tecnis Symfony (Johnson & Johnson Vision). This is a single-piece, hydrophobic acrylic, foldable lens with a biconvex, wavefront-designed anterior aspheric surface, an addition of +1 .75D at the IOL plane and an echelette design to correct chromatic aberrations and theoretically improve depth of focus. However, research shows that although the correction of chromatic aberrations improves contrast sensitivity it does not increase depth of focus.
Another of the new multifocal-EDOF hybrids is the AcrySof IQ PanOptix (Alcon), a diffractive trifocal unapodised lens. It distributes light to four focal points, with half of the light devoted to distance and half devoted to near and intermediate with respective addition powers of +2.17D and +3.25D. The posterior lens surface is spherical, and the anterior surface is aspheric, with a central 4.5mm diffractive portion.
Among the new refractive multifocal-EDOF hybrids is the Acunex Vario (Teleon), which has a unique sectorial optic design with a 1.5D addition with a smooth transition between zones to provide an extended depth of focus with sharp visual acuity results for the intermediate and distance ranges.
Other options include phakic and piggyback multifocal IOLs such as the Presby IPCL (Care Group) which has a trifocal diffractive optic, designed for phakic presbyopic patients. There are also piggyback multifocal IOLs such as the Sulcoflex (Rayner), the ReSTOR (Alcon), AT Lisa (Zeiss), and Mplus (Oculentis). Although these implants can provide good results, success with the lenses is highly dependent on a near perfect alignment of the optical axes of the piggy-back and primary IOLs.
Finally, there is the re-emergence of the accommodating lens, now with new technologies that no longer attempt to use the forward movement of the optic to achieve accommodation. Among these new IOLs is the AkkoLens Lumina, which uses two optical elements shifting perpendicular to the optical axis to produce accommodation. Studies with the lens to date have shown that it can restore visual function and accommodation, with no effect on the contrast sensitivity, Prof Alió said.
Jorge Alió: firstname.lastname@example.org