Extended depth-of-focus IOLs may provide improved visual performance

October 18, 2016
Clark Y. Chang, OD, MSA, MSc, FAAO

Dr. Chang is a subinvestigator in numerous clinical trials. He is immediate past president of New Jersey Academy of Optometry, and an advisory board member for International Keratoconus Academy for Eye Care Professionals (IKA), Gas Permeable Lens Institut

,
Jim Owen, OD, MBA, FAAO

As your patients celebrate another birthday milestone, they are again back in your chair wondering why their reading glasses mysteriously disappear when they are out exploring life or why their arms are not as long as they used to be.


As your patients celebrate another birthday milestone, they are again back in your chair wondering why their reading glasses mysteriously disappear when they are out exploring life or why their arms are not as long as they used to be. Do the above patient scenarios sound like déjà vu?

Before you examine the validity of a conspiracy theory that every presbyope is against you, please understand that this dreaded discussion about presbyopic corrections is gut-wrenching for both doctors and patients.

There may be a constellation of options available-glasses, contact lenses, or refractive surgeries-and yet each has its own associated compromises that your patients have to comprehend.

Related: Caring for the post-operative cataract patient

Upon vaguely grasping the comparative concepts of monovision and multifocals, the potential visual compromises become more daunting when some treatment modalities appear not to be easily reversible, that is, surgery. Nonetheless, we are fortunate in that both our optical and surgical options continue to innovate and grow.

With cataract surgery being one of the most common ophthalmic surgeries performed in the world-and the rising demand for a better quality of life from our patients­-the refractive benefits of a well-planned cataract surgery are immense.

Patients often want to actively engage you in these presbyopic discussions. It is estimated that nearly 4 million cataract procedures are performed each year, and as the baby boomer population grows older, this number will only continue to trend upward.1

Meeting patients' IOL expectations

Despite established monovision strategies with monofocal intraocular lenses (IOL) and a plethora of premium multifocal IOL options, patients continue to desire better functional outcomes that have a more continuous range of post-procedural vision.

Patients also wish for less optical aberration-related limitations-most notably night haloes and glare. The latest IOL innovation is Tecnis Symfony and Tecnis Symfony Toric (Abbott Medical Optics), which will be available to U.S. patients in late 2016.

Related: Top 6 reasons to refer for cataract surgery

Symfony and Symfony Toric represent a new category of premium IOL with a novel optical concept called extended depth of focus (EDOF), which may make our conversation more palatable for patients who want more visual freedom after surgery.

 

Previous multifocal designs distribute light energy in such a ratio where zones of discontinuities, typical in the near to intermediate visual range, may be noticeable to patients. These compromises may not only lead to insufficient visual competencies during near and/or intermediate activities, but they could also lead to reduced IOL performance in dim lighting, including haloes and glare.

The Symfony lenses with EDOF design incorporate a proprietary diffractive echelette pattern, which provides more continuous light energy distribution, leading to an elongation of depth of focus. Thus, the built-in EDOF optical feature results in an extended range of focusable light rays across multiple reference distances, allowing continuous vision connecting far to intermediate and into near focal points.2

Related: Will the SMILE procedure replace LASIK?

Another subjective restriction observed by many patients with previous multifocal IOL designs is that these IOLs may not provide patients with consistent visual quality across different illumination levels. The typical complaint of poor vision in dim light has been associated with increases in spherical aberrations in the optical system and decreases in contrast sensitivity.3

In addition to EDOF, Symfony lenses also have a unique blend of optical features overcoming notable refractive limitations from previous generations of premium multifocal IOLs. In order to combat the adverse influences of spherical aberration, Symfony lenses include a wavefront-designed anterior aspheric surface and biconvex curvatures in its anterior and posterior optical surfaces.

Related: An OD’s perspective on his own cataract surgery

The aspheric optics can assist in better alignment of paraxial and marginal light rays at the retinal plane, which maintains good image quality and contrast sensitivity across different light settings despite pupil sizes.

Symfony’s proprietary achromatic technology also helps to preserve contrast sensitivity as well as reduce symptoms of dysphotopsia, such as chromatic aberrations.2,4 These results have been clinically demonstrated in Symfony’s FDA study data.5

Symfony shines in FDA study

The FDA randomized, multicenter clinical trial was conducted across 15 investigation sites. In this study, 148 patients who received Tecnis Symfony were compared to 150 patients who received Tecnis monofocal lens. For near vision (40 cm), Symfony group saw significantly better at near vision than the monofocal group and, when measured binocularly, the Symfony group saw between 20/25 and 20/30 at the designated near working distance.

 

Additionally, patients with Symfony achieved 20/20 vision at the intermediate range (66 cm). While there was not a difference in distance vision between the two lenses, there was a significant increase in lines of vision at both intermediate and near vision in eyes with Symfony when compared to the group who received Tecnis monofocal. As expected, the adverse events did not differ between the two groups.5

Related: Selecting topical regimens for cataract patients

No significant difference was noted in contrast sensitivity across multiple spatial frequencies under mesopic conditions when comparing Symfony groups to the monofocal control group. In the FDA study, fewer than 3 percent of patients spontaneously reported significant night vision symptoms with a low incidence of glare and halo.

This quality of vision appears to hold across varying pupil sizes as demonstrated by the limited loss of modulation transfer function (MTF) when the pupil size increased from 3 to 5 mm.5

It is not often that we benefit from both sphere and toric premium IOL receiving simultaneous FDA approval. With the toric lens, 92 percent of patients were reported to have less than 0.50 D of residual astigmatism. In addition, the toric lens has a nearly identical defocus curve when compared to Symfony spherical, which means that the Symfony toric can provide the same benefit of improved intermediate and near vision.5

Related: Charting new directions in glaucoma treatment

Up until now, there has been a limited availability of toric IOLs that offer multifocal optics. Symfony toric IOL will allow eyecare providers to offer a new and viable option to patients with corneal astigmatism.

While Symfony family of lenses and its EDOF design concept couldn’t come soon enough, it is with anticipated excitement that we await to witness the positive improvements that these IOL options can bring to our patients who desire more functional post-operative visual performances. 

As well, we expect that IOL technologies will only continue to improve from here and we can hardly wait to see what the future may bring next.

References:

1. MarketScope, LLC. 2016 IOL Report: A Global Market Analysis for 2015 to 2021. Market Scope, LLC.

2. Abbott Medical Optics. TECNIS Symfony Extended Range of Vision IOL Package Insert. Available at :  http://www.tecnisiol.com/eu/tecnis-symfony-iol/files/symfony-dfu.pdf. Accessed 10/12/16.

3. Unsal U, Baser G. Evaluation of Different Power of Near Addition in Two Different Multifocal Intraocular Lenses. J Ophthalmol. Jun 2016;2016:1395302.

4. Hillen, M. Mission: Impossible. Ophthalmologist. 2016 August. Available at: https://theophthalmologist.com/issues/0716/mission-impossible/. Accessed 10/12/16.

5. Food and Drug Administration. Press release: FDA approves first intraocular lens with extended range of vision for cataract patients. 15 July 2016. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm511446.htm. Accessed 10/12/16.