Presbyopia correction, using the latest technological advances in intraocular lenses, has proved to be something of a revolution for patients. It has allowed them to have their cataracts treated and then provided the opportunity to improve their vision without glasses. For many, post-cataract vision is the best they have ever seen.
As the largest provider of premium spherical, toric and presbyopia-correcting IOLs in the UK, Optical Express is committed to staying abreast of current technology and to investigating any new advances that can benefit our patients. In our model, the examining optometrists conduct the preoperative examination and educate the patient about the risks, range of potential outcomes, alternatives and benefits of various surgical options.
In further discussion with the patient, the surgeon makes the final lens decision and completes the informed consent process, most commonly on the day of surgery. All patients are recommended to see the surgeon in advance of surgery. However, the vast majority elect to meet the surgeon on the day. Both eyes are typically treated on sequential days, with routine follow-up at one day, one week, three months, and annually thereafter.
We currently offer choices ranging from premium aspheric monofocal lenses through to functional (low) add lenses and high-add multifocals. The middle category includes both low-add multifocal IOLs and the relatively new Tecnis Symfony extended range of vision IOL (Abbott Medical Optics), which incorporates compelling new technology.
Tecnis Symfony
The Symfony lens has diffractive optics, but it is not a traditional multifocal that splits light into two or three focal points. Instead, its ‘echelette’ design produces a novel pattern of light diffraction that elongates the focus in the eye (Figure 1) to produce a continuous range of vision (Figure 2). The US Food and Drug Administration (FDA) has had to create a new lens category based on the unique optical properties of the Symfony, calling it ‘extended depth of focus’.
Unlike a multifocal, it directs all of the incoming light to the retina. And because the focus is elongated rather than having distinct peaks, the brain doesn’t have to suppress the secondary focal points, reducing the chance of ghosting or halos. In clinical studies, and in our own experience, the incidence of glare and halo is similar to that of a monofocal IOL.
The trade-off of the extended range is some loss of acuity at the very near range. We have found, however, that this has little impact on patient satisfaction.
The optical quality is another technological advance that bears explaining. Tecnis Symfony incorporates achromatic optics that reduce the eye’s natural chromatic aberration – the small degree of blur that comes from the difference in how light at opposite ends of the visible spectrum focuses on the retina (Figure 3). By bringing longer wavelength visible red and shorter wavelength blue/violet light into tighter focus, the achromatic design (especially when combined with correction of spherical aberration), enhances retinal image quality without any negative effect on the depth of focus.1,2
The result is a lens that provides very sharp distance vision with near to intermediate vision that is very functional and perfectly adequate for using, for example, a mobile phone or computer, reading the newspaper, and most other common daily near vision tasks. Less time is spent counselling patients about glare and halo and about adaptation, because patients seem to adapt to this lens faster than they do to multifocal technologies. And, because it is also available in the UK in a toric version, it can be offered to a wide range of patients.
Clinical results
After one year of experience with the Tecnis Symfony, clinical data reveals excellent results.
The lens has been implanted in 4,464 eyes of 2,702 patients at Optical Express, including more than 300 eyes with the toric version of the lens.
The mean age of patients implanted is 56.9 years (range, 36 to 88 years). Eyes with a wide range of refractive error, from -14.13 DS to +8.38 DS, with up to 3.75 DC of astigmatism, were treated.
Postoperatively, the mean manifest spherical equivalent for all eyes was -0.27 ±0.56 D. At the last follow-up exam, the mean monocular uncorrected distance visual acuity (UCDVA) was 0.06 ±0.18 (20/20-3) and mean binocular UCDVA was -0.03 ±0.11 (20/20+1), with 99% of patients seeing well enough to be able to reach the driving test standard without correction.
Uncorrected near visual acuity was 0.31 ± 0.17 monocularly and 0.24 ± 0.14 binocularly at the last visit, with the majority seeing N5 or better (Figure 4). Patients were very satisfied with these outcomes and 92% said they would recommend surgery with the Symfony lens to a friend when completing a post-treatment questionnaire.
Although ophthalmic surgeons at Optical Express have a range of intraocular lenses available to them from which they can choose freely, with these results the Tecnis Symfony has become the premium lens of choice to use for many patients. Each patient’s clinical and lifestyle requirements are taken into careful consideration during the consultation process, of course. In most cases, the combination of achromatic lens technology and advanced diffractive optics means that the clinical team can offer patients the kind of functional vision they demand without the side effects they would prefer to avoid.
Looking ahead
There are still exciting advances to come in presbyopia correction. We may, for example, see further developments in optical quality and lenses that can be implanted through smaller incisions. Further into the future yet, one can envision a time when the multifocality of a lens could be adjusted or removed or when we could offer patients a truly accommodative IOL. In the meantime, we already have presbyopia-correcting technology that is a marked improvement over the multifocal technology of just a year ago.
Stephen Hannan is clinical services director for Optical Express
References
1 Weeber HA, Piers PA. Theoretical performance of intraocular lenses correcting both spherical and chromatic aberration. J Refr Surg 2012;28 (1):48-52.
2 Artal P, Manzanera S, Piers P, Weeber H. Visual effect of the combined correction of spherical and longitudinal chromatic aberrations. Opt Express 2010;18(2):1637-48.