How Is Extended Depth of Focus Achieved with a Small-aperture Lens?

Life happens on small and grand scales, right in front of us and from afar; most of us want to experience all of it. Since the first bifocal IOLs were developed in the 1980s, scientists and manufacturers have been on a dedicated mission to provide individuals with great vision at all distances after cataract surgery. Following those early bifocal lenses, the development of multifocal lenses provided good vision at multiple distances, and accommodative IOLs attempted to mimic the focusing ability of the natural eye. However, although many of these options have been successful in achieving good visual acuity at distinct distances, this has often come at the price of decreased overall quality of vision.1-3 Rather than creating two or three focal points, extended depth of focus (EDOF) technologies aim to increase overall depth of field, creating a fluid visual experience that provides better near vision than monofocal technologies and, at the same time, less trouble with glare and halos than multifocal IOLs. There are a number of EDOF lenses on the market, and they achieve their desired visual range via a variety of methods. The Symfony IOL (Abbott Medical Optics) has a unique echelette design. (The manufacturer refers to this lens as providing an extended range of vision, as opposed to EDOF.) The Light Adjustable Lens (Calhoun Vision) can be shaped to provide additional spherical aberration through postoperative irradiation of the silicone material with ultraviolet light.4