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Accommodating IOL technology continues to evolve
Newest dual-optic design more closely mimics natural accommodation and properties of the crystalline lens.
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Although we are fortunate to have a number of options for the correction of presbyopia at the time of cataract surgery, the current options either have some inherent compromises, as in the case of multifocality, or do not consistently provide good uncorrected near vision, as seen with single-optic accommodating IOLs.
Dual-optic accommodating IOLs were developed to try to address these shortcomings. The combination of a high-plus anterior optic with a negatively powered posterior optic restores accommodation by causing a change in optical power with the movement of the ciliary muscle. The anterior optic moves forward on accommodating effort, sharpening the near focus.
The first such IOL, the Synchrony (Abbott Medical Optics), has been successfully used for several years in Europe and other areas outside the United States. But as we continue to perfect dual-optic IOL design, it is desirable to more closely mimic natural accommodation, which results in an increase in the optical power of the crystalline lens and in negative spherical aberration. Additionally, the central region of the natural lens exhibits greater change in optical power compared to more peripheral regions.
New-generation lens
A new-generation dual-optic lens, the Synchrony Vu, is attempting to take advantage of these properties. It has a central aspheric zone with negative spherical aberration that blends into a peripheral spherical optic. In theory, this design should allow the lens to utilize pupil constriction during near viewing to maximize the near benefit from the central aspheric zone without degrading optical image quality.
Eduardo F. Marques
Through extensive ocular modeling, it was determined that a 2.5-mm central zone and 2.1 D peak power provides the best balance between optical quality and depth of focus. Modeling showed that this combination provides about 1 D greater depth of focus while still meeting ISO standards for optical quality of monofocal IOLs.
We recently evaluated the performance of this new IOL in patients enrolled at clinical sites in Spain and Portugal. In a prospective, non-randomized study, 61 eyes of 31 cataract patients were implanted with the Synchrony Vu lens. The mean age of subjects enrolled was 70.0 ± 7.5 years.
Monocular and binocular visual acuities were measured with an ETDRS chart at far (4 m), intermediate (80 cm) and near (40 cm) distances. Mesopic contrast sensitivity was measured with the Optec 6500 functional acuity test (Stereo Optical) with and without glare. A subjective questionnaire about visual symptoms was also administered.
Clinical results
Six months postoperatively, 97% of patients had 20/40 or better uncorrected binocular near visual acuity (Figure 1), and 90% achieved 20/40 or better distance-corrected binocular near (Figure 2). Intermediate vision was also excellent. Mesopic contrast sensitivity was within normal limits, both with and without glare.
The mean sphere was −0.25 ± 0.62 D, mean cylinder was −0.76 ± 0.57 D and the mean spherical equivalent was −0.63 ± 0.61 D. More than 80% of eyes were within 1 D of plano. The minimum add required to achieve threshold near visual acuity was 1.28 ± 0.45 D.
When we asked patients about their spectacle use, 68% said they never needed spectacles at any distance. Of those who needed spectacles at least occasionally, patients were about twice as likely to use spectacles for near tasks as for far or intermediate.
Overall, 93% of patients achieved functional uncorrected binocular visual acuity of 20/25 or better for far and 20/32 or better for intermediate and near. Glare and halo were reported as mild or nonexistent by 80% of patients (Figures 3 and 4).
Based on our findings, next-generation dual-optic accommodating IOLs provide good near and intermediate vision without sacrificing distance visual acuity or quality of vision, something that is important to demanding presbyopic patients. As this technology continues to evolve, dual-optic accommodating IOLs with enhanced optics can be a significant addition to the armamentarium of options for cataract surgery patients who desire good uncorrected vision at all distances.