Extended Depth of Focus Intraocular Lenses for Presbyopia

Sruti S. Akella; Viral V. Juthani


Curr Opin Ophthalmol. 2018;29(4):318-322. 

In This Article

Extended Depth of Focus: Optical Principles

The human eye is designed to focus light on the fovea, but even a healthy eye will experience some degree of ocular aberrations, which significantly affect the quality of retinal images.[5] These aberrations are mainly classified as monochromatic (defocus, astigmatism, spherical, and coma) or chromatic (longitudinal and transverse). Monochromatic aberrations are intrinsic properties of the eye and lower-order aberrations can be corrected with contact lenses, spectacles, and intraocular lenses. However, correction of chromatic aberrations has also been shown to improve retinal image contrast.[6,7] The field of refractive surgery therefore has been increasingly interested in targeting correction of chromatic aberrations, especially with IOLs. This is particularly relevant for the cataract surgeon, as previous work has shown that most pseudophakic chromatic aberration is caused by chromatic dispersion from IOLs.[8]

EDOF lenses work by focusing incoming waves in an extended longitudinal plane, as opposed to the monofocal lenses which focus plane waves in one single point or two to three discrete points (bifocal or multifocal, respectively). This elongated focus is meant to eliminate the overlapping of near and far images caused by traditional multifocal IOLs, thereby eliminating the halo effect. Theoretical studies have shown that the EDOF lenses provide better optical quality on the whole addition range than multifocal and monofocal lenses.[9]

Another subtype of enhanced depth of field IOLs is so-called small aperture IOLs. These lenses are designed with a pinhole that blocks unfocused rays of light that can potentially degrade image quality. Reducing the pupil aperture allows only central-focused light to reach the retina, resulting in a high-quality extended depth of focus without blurry transition zones.