Differences in lenses
The Comfort lens is a purely refractive lens with a high light transmission. It is rotationally asymmetric with a sector-shaped segment on the anterior surface providing +1.5 D for improved intermediate vision. Due to a transition zone between both segments, it can be considered an extended-depth-of-focus (EDOF) lens rather than a bifocal IOL.
The Symfony lens has a diffractive posterior surface that generates a continuous focus with an effective addition of about +1.78 D. Combining this diffractive posterior surface with a refractive anterior surface, the Symfony, a EDOF lens, provides reduced chromatic aberration leading to improved contrast sensitivity.
In many ways, the two lenses are comparable, Dr. Breyer noted. Measured clinical defocus curves for Comfort lens and Symfony lens are virtually identical, with no statistically significant (p < 0.05) differences between mean visual acuity values from 0.0 D to -2.5 D (see Image 1).
Measuring both IOLs on an optical bench, the modulation transfer function (MFT) focus through curves show similar characteristics. Symfony is somewhat better in the intermediate range, but it is difficult to translate optical bench values to clinical outcomes.