A New Read on Presbyopia
Currently, our options for correcting presbyopia at the time of cataract surgery are traditional multifocal IOLs, accommodating IOLs, monovision with monofocal IOLs and now the new Tecnis Symfony IOL (Abbott Medical Optics). Traditional multifocal lens implants use diffraction, which allocates light to multiple focal points by creating zones on the anterior surface of the lens. This allows for simultaneous viewing of images at distance and near. Accommodating IOLs hinge forward by their haptics as the natural ciliary muscle contracts and relaxes to provide near vision focus.
Independent research on the new Symfony lens is limited at this time, but its manufacturer says it was designed with what’s called an extended range of vision to provide clear vision though a limited depth of focus without splitting light or changing position.1 The lens has refractive echelettes, which appear as concentric rings and have a similar appearance to traditional multifocal lenses at the slit lamp.1 These echelettes do not split the light into different foci; rather, they introduce a pattern of light diffraction that elongates the focus of the eye, providing an extended range of vision.
AMO also says the lens design corrects for spherical and chromatic aberrations, and that the aspheric anterior surface and posterior achromatic diffracting surface provide great retinal image quality and contrast sensitivity.1 The Symfony also has a toric version for astigmats.
The manufacturer says contrast sensitivity with Symfony is similar to that of monofocal IOLs, which may be better than that obtained with a multifocal IOL due to the latter’s splitting of light. Instead, AMO says, Symfony images are not out of focus, causing fewer halos.1
Sacrificing Near Vision
Despite its advantages, this new lens may not provide the same near vision obtained with traditional multifocal lenses, and clinicians must keep this in mind with patients whose work or hobbies require precise near vision. Some cataract surgeons may compensate for this by using bilateral Symfony lenses and leaving the non-dominant eye slightly myopic, in the -0.75D to -1.00D range.
Preoperatively, we have to keep in mind other ocular pathologies (e.g., severe ocular surface disease, corneal dystrophy, retinal pathology) that would limit patients’ quality of vision after cataract removal and make them less than ideal candidates for this lens.
Clinicians must check distance, intermediate and near vision at all post-op visits. To ensure patient satisfaction, we need to ask patients how their “new eyes” are functioning during activities of daily living. While most achieve positive outcomes, it’s important to reassure those with less than ideal outcomes that you will work closely with them and their surgeon to address any concerns. Luckily, these conversations, in our experience, are few and far between.
Staying up to date on the latest IOLs allows us to better educate patients on this important decision. Often, patients are unaware they could possibly regain some of the range of vision they used to have.
|1. Abbott Medical Optics. Tecnis Symfony IOL. 2017. Available at www.vision.abbott/us/iols/extended-depth-of-focus/tecnis-symfony.html. Accessed March 8, 2017.|