There are a number of ways to improve near vision for presbyopes, including multifocal intraocular lenses (IOLs)–traditional or low add–and pseudoaccommodative IOLs. It has been well documented that a small pupil and higher order aberrations, such as spherical aberration (SA) or coma, can increase depth of focus.1
In combination with some degree of monovision, this may enable some patients to have good near vision with a monofocal IOL or a corneal refractive treatment. However, there may be tradeoffs in terms of visual quality.
The ophthalmic industry is beginning to see a new category of extended depth of focus (EDOF) IOLs that are designed to provide a continuous range of focus with fewer limitations than multifocal IOLs or the pseudoaccommodative options described above. These include the Tecnis Symfony IOL (Johnson & Johnson Vision/AMO), which relies on diffractive echelette optics to elongate the focal line, and the small-aperture IC-8 IOL (AcuFocus), which is not yet available in the United States, as well as other designs in development.
Advantages vs. multifocal
The EDOF category offers two advantages over traditional multifocal IOLs. First, it offers a natural range of vision, rather than one or two “sweet spots.”
This can be easy to explain to a patient who has worn bifocal or trifocal spectacles. They understand that each portion of their spectacle lens has a limited range, beyond which there is a blur. While patients can adapt to spectacles or multifocal IOLs with distinct focal points, the idea of having a broader field of clear vision with an EDOF lens is attractive.
Additionally, because EDOF lenses do not split light among focal points the same as a multifocal IOL, there is minimal-to-no loss of distance clarity and contrast acuity. Since patients do not have to suppress the second (blurred) focal point, they are less likely to experience ghosting, haloes, or “waxy” vision. It also lowers my level of concern about the impact of a presbyopia-correcting IOL in the context of other anterior segment conditions.
Because of this, I will consider an EDOF lens for post-refractive eyes (with regular corneal astigmatism and a well-centered ablation bed) and for patients with early Fuchs or mild-to-moderate dry eye disease that responds to treatment. I still do not recommend any presbyopia-correcting lens, including EDOF, for patients with any evidence of macular pathology.