The most implanted intraocular lenses (IOLs) in cataract surgery are the monofocal lenses. A monofocal IOL has equal power in all regions and a single zone of clear focus, producing excellent vision from a determined distance. Typically, they are effective in restoring satisfactory distance vision, which means wearing eyeglasses for reading or close work.
However, many patients require spectacle correction for intermediate and near vision, even after surgery. Thus, multifocal IOLs were designed to meet the increasing demand from patients for spectacle independence. For providing far, intermediate and near vision simultaneously, multifocal IOLs possess two or more independent focal points corresponding to different dioptric powers. Critical aspects of multifocal lenses, whether they use refractive or diffractive optics, are related to the principle of simultaneous vision, in which while an image is in focus, the image out of focus is suppressed.
Multifocal IOLs are designed to split light into different foci. However, the division of light that occurs as it passes through a bifocal and above all a trifocal IOL is also responsible for the optical phenomena (e.g., glare and halos) and the loss of contrast sensitivity that occurs after implantation of such IOLs, thus reducing visual quality.
In an attempt to achieve good quality of vision at all distances, while avoiding undesirable photic phenomena, a new generation of IOLs was introduced, the extended depth of focus (EDOF) IOLs.
In 2014, the FDA recognized the EDOF IOLs as a “new product category intended to enhance near and intermediate visual performance while having minimum impact on distance performance”. The Agency noted that “EDOF IOLs could have advantages over the multifocal IOLs including a lower rate of glare and halos and less loss of contrast at distance focus, although visual performance improvement at near may be modest or absent”.
The basic principle behind EDOF technology is to create a single elongated focal point to enhance the depth of focus and provide a continuous range of vision.
While multifocal IOLs aim at providing spectacle independence for both near and distance vision by dividing light into two or more foci, EDOF IOLs improve the extension of clear vision without splitting the light beam.
The incident beam is not divided:
SIFI EDOF IOLs Mini WELL and Mini WELL Toric provide a high level of spectacle independence at all distances and ensure good vision while using computers, tablets and smartphones with less contrast reduction and fewer photic phenomena commonly associated with multifocal IOLs.
Future trends for EDOF IOLs will involve the improvement of vision for near distance.
To view SIFI's EDOF IOLs click here.
Product Concept and Optics Design
The optic development of this lens is based on a patented engineering innovation exploiting the wavefront aberrations to increase the depth of focus in order to generate an uninterrupted vision from near (40 cm) to far without gaps of vision.
Unlike to other multifocal IOLs on the market (refractive/diffractive), Mini WELL does not have a discrete number of foci but a continuum of foci which depends on its innovative optics using the spherical aberrations.
The patented innovative technology of the Mini WELL utilizes the spherical aberrations, induced in the central part of the IOL only, to deliver depth of focus allowing the correction of presbyopia without compromising distance vision especially at night.
Differently from IOLs with diffractive optics, where concentric circles are present and a prismatic effect is used, the optics of the Mini WELL has three (3) zones where different spherical aberrations are applied. Those zones are not visible.
The transition areas of the three optical zones are smooth and optically efficient.
For this reason, an uninterrupted high-quality vision at all distances in a progressive manner is possible without “jumps” of vision or halos.
The presence of a continuum of foci results in a progressive multifocality (elongated focal point) that positively affects the performance of this IOL providing good uninterrupted quality of vision at all distances without annoying incidences of dysphotopsia phenomena.
To view SIFI's EDOF IOLs click here.