Extended Depth of Focus IOLs
Extended Depth of Focus (EDOF), or Extended Range of Vision, is a new technology that has recently emerged in the treatment of Presbyopia-correcting IOLs. In contrast to multifocal intraocular lenses (IOLs) used in treatment of presbyopia, EDOF lenses work by creating a single elongated focal point to enhance “range of vision” or “depth of focus”.
Many factors including chromatic aberration can cause image degradation in pseudophakic eyes. A previous study found that most pseudophakic chromatic aberration is caused by chromatic dispersion from IOLs as compared to the cornea. The average eye has approximately 2.0 diopters (D) of chromatic aberration for wavelengths between 400nm and 700nm and 0.8D for wavelengths between 500 nm and 640 nm. Correction for this type of image degradation with achromatic IOL technology has, in previous studies, been shown to improve image quality and contrast sensitivity in pseudophakic eyes.
As of July 15th 2016, the TECNIS Symfony IOL (Abbott Medical Optics, Inc. of Santa Ana, California) is the first FDA approved lens of its class. The IOL has a biconvex wavefront-designed anterior aspheric surface and a posterior achromatic diffractive surface with an echelette design (Figure 1). This proprietary format creates an achromatic diffractive pattern that elongates a single focal point and compensates for the chromatic aberration of the cornea. Its overall diameter is 13.0mm, with an optical zone of 6.0mm, and is available in power ranges from +5.0 to +34.0 D, while incorporating an ultraviolet light-absorbing filter.
A recent comparative study found the Symfony IOL achieved significantly better postoperative uncorrected monocular and binocular distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities when compared to the monofocal Tecnis ZCB00 IOL (P ≥ .013). 
A large prospective multi-center study demonstrated that the Symfony IOL provided comparable clinical outcomes in distance visual acuity to monofocal and current multifocal lens technologies, and possibly better intermediate visual acuity outcomes compared to current multifocal technology, with high levels of patient satisfaction.  411 patients who had bilateral implantation of the extended range of vision IOL, with intended micro-monovision in 1 group (monovision group) and intended emmetropia in the other group (non-monovision group). The mono-vision group was comprised of 112 patients, while the non-monovision group was made up of 299 patients. The mean decimal uncorrected distance (UDVA), intermediate (UIVA), and near (UNVA) visual acuities were 0.95, 0.81, and 0.69, respectively, 4 to 6 months postoperatively. Significantly better UIVA (P = .003) and UNVA (P = .011) were found in the monovision group than in the non-monovision group. Spectacle independence was high, with only 14.4% of eyes requiring reading spectacles frequently. In the same study, dysphotopsias (halos, glare, or starbursts) were reportedly low, with more than 90% of patients reporting no or mild halos, glare, starbursts, or other photic phenomena.
IOL implantation after cataract extraction, or as part of refractive lens exchange, is a relatively safe procedure. However, risks that come with invasive eye surgery are still significant and may include, but are not limited to infection, increased IOP, corneal edema, posterior capsular opacification (PCO), IOL decentration, macular edema, and retinal detachment. Severe, vision threatening infections (e.g. endophthalmitis) are rare, but possible, adverse events associated with any intraocular surgery.
High levels of patient satisfaction were achieved in an initial study. One hundred two patients (91.1%) and 283 patients (94.6%) in the monovision and non-monovision groups, respectively, said they would recommend the same procedure to their friends and family. In the entire cohort of 411 patients, 385 (93.7%) would recommend the surgery and 388 (94.4%) would choose the same IOL again.
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