Synchrony IOL shows long-term accommodative ability

Accommodative IOLs offer the potential advantage of producing spectacle independence following crystalline lens extraction without the optical aberrations that are inherent in multifocal IOLs. In order for accommodative IOLs to compete with multifocal lenses, they will need to consistently deliver large amplitudes of accommodation. Although single-optic accommodative IOLs are being utilized in the U.S., dual-optic IOLs such as the Synchrony offer the potential for greater accommodative amplitudes and greater percentages of spectacle independence. The Synchrony IOL, because of its unusual design, does require additional demands on the surgeon for creating an adequately sized and well-centered capsulorhexis, complete cortex removal and rhexis polishing through the small diameter rhexis, and care with injection of the IOL into the capsular bag. However, the added advantages of a dual-optic IOL should validate its utilization once FDA approval arrives.

In this month’s column, John Vukich reviews the Synchrony accommodative IOL and some of the important clinical data that substantiates its efficacy.

Richard Hoffman, M.D.,
Column Editor

The Synchrony dual-optic accommodative intraocular lens provides enhanced near vision and compares favorably to diffractive multifocal IOLs

Synchrony lens
Source: Abbott Medical Optics

The quest to find an accommodative intraocular lens (IOL) has dramatic implications for how we treat our patients. I believe it would represent a paradigm shift in what we can offer to our patients at various ages and if we can create a lens that truly provides reliable accommodation, I believe it will fundamentally change the way we practice ophthalmology.

Designing accommodation

The Synchrony IOL (Visiogen, Abbott Medical Optics, AMO, Santa Ana, Calif.) is a single-piece dual-optic, silicone lens designed to mimic the natural lens. It has a 5.5 mm high plus anterior optic of +32 D, coupled to a 6.0 mm negatively powered posterior optic. The concept is that these two lenses are separated by a spring-activated mechanism. The haptics separate the lenses at a given distance under constriction of the capsule, and during relaxation of the capsule following accommodative effort, anterior movement of the positive anterior optic produces increased power for near tasks.
The function of the IOL suggests there is some mechanical advantage to filling the capsular bag. I think it is important to not discount the angular insertion of the zonules anteriorly and posteriorly to the equator. Perhaps it is not an inevitable consequence that the zonules, particularly the posterior zonules, will become fibrotic with age, which could be a consequence of inactivity.
The surgical technique when implanting the Synchrony is one of standard cataract surgery with particular attention being paid to the anterior capsulotomy, which is a critical component to the function of the lens. The capsulotomy must be well centered and small. It also needs to be intact because it creates a mechanical system that will be under tension.
The lens is then inserted through a 3.8 mm incision using a proprietary injector system that injects the posterior optic first, followed by the anterior optic. The post-op regimen also is similar to standard cataract surgery with perhaps a slightly longer treatment with anti-inflammatory drugs; although it is not yet clear if the extended use of anti-inflammatories is necessary.

Reviewing the results

We now have a number of patients around the world who are three years out from surgery. At the 2009 ASCRS Symposium in San Francisco, Victor Bohorquez, M.D., Servioftalmos Department of Ophthalmology, Bogotá, Colombia, presented his two-year follow-up data on 19 patients who had bilateral implantation. Their best-corrected distance visual acuity (BCDVA) at one year and two years post-operatively were 20/28 and 20/23, respectively.
It is interesting to note that the patients’ visual acuities improved from the first year to the second year. This could be the result of neuro-adaptation or exercises that improve the eyes’ ability to move the lens.
Similarly, the improvement also is reflected in the reading speed at one year and two years post-operatively. Even with increasingly smaller optotypes, the reading speed was actually better at two years than at one year.
Also at the 2009 ASCRS Symposium, Ivan Ossma, M.D., M.P.H., clinical professor, Universidad Industrial de Santander, Bogotá, presented results from a randomized, double-masked trial of the Synchrony compared to the ReStor multifocal IOL (Alcon, Fort Worth, Texas). In the study, 100 patients were randomly assigned to receive bilateral implantation of the Synchrony (50 patients) or ReStor (50 patients).
The study was looking at binocular and monocular visual acuity at 6 and 12 months post-operatively at near, intermediate and distance visions.
The uncorrected distance acuity was statistically similar in each eye with more than 90% of the patients achieving 20/20 or better visual acuity.
What were statistically significant, however, were the distance-corrected and intermediate visual acuities. The Synchrony was better at 60cm, 80cm, 1m, and 2m (2-tailed t test, P<0.001), but they were similar to the ReStor at 40cm and 4m.
None of the Synchrony patients complained of “severe” or “very severe” halos or glare compared to 31.4% and 20% of the ReStor patients, respectively (Fischer’s Exact test, P<0.001). There were, however, reports of moderate glare by Synchrony patients at a similar rate as ReStor patients.
The Synchrony also provided significantly better contrast sensitivity than the ReStor in photopic and mesopic conditions.

Long-term accommodation

There is long-term objective evidence of the Synchrony’s accommodative ability.
Douglas D. Koch, M.D., professor and the Allen, Mosbacher, and Law Chair in Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, demonstrated ultrasound biomicroscopy (UBM) accommodation of five eyes at one year at the 2009 ASCRS Symposium. The UBMs were taken under cycloplegic and accommodative conditions at 6 and 12 months post-operatively, and then they were repeated at two years along with an iTrace Visual Function Analyzer (Tracey Technologies, Houston).
The two methods independently confirmed the mechanism of accommodation in the same eye of just under 3 D.
Long-term capsule clarity always is a concern with IOLs, but after three years of follow-up, we now know that Nd:YAG laser treatments are rarely used (4/209, or 1.9%) and the laser did not negatively affect accommodative ability. The complete filling of the capsular bag seems to have some restrictive effect of cellular migration and posterior capsular opacification (PCO).
So in conclusion, the Synchrony provides long-term accommodation leading to enhanced near vision. It compares favorably to diffractive multifocal IOLs currently in the U.S. market, and the YAG rate appears to be low.

Dr. Vukich is an assistant clinical professor at the School of Medicine and Public Health, University of Wisconsin, Madison. He has financial interests with Abbott Medical Optics (Santa Ana, Calif.). Dr. Vukich can be reached at 608-282-2000 or javukich@gmail.com.