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Toric multifocal IOL now an option for cataract surgery patients
The Tecnis Symfony provides a solution for patients with astigmatism.
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With advancing technology, cataract surgery is now less invasive, resulting in better recovery and outcomes. Not only have the surgical techniques for cataract extraction improved, but the quality of and options available for IOLs have increased as well.
On July 15 the FDA approved the Tecnis Symfony lens from Abbott Medical Optics, an extended depth of focus IOL that provides a full range of continuous high-quality vision after cataract surgery, in standard monofocal and toric.
The Symfony IOL increases depth-of-focus at all distances continuously and also has five toric IOL options to correct corneal astigmatism. Traditional monofocal IOLs correct vision only at distance, resulting in dependence on glasses, contact lenses or refractive surgery to meet all of the patient’s visual needs. Also, previous multifocal IOLs only corrected specific foci, leaving deficiencies in vision in the areas between the foci.
Symfony optics
Unlike monofocal IOLs that provide a fixed focus point at one particular distance, the Symfony elongates the range of focus of the eye and provides a continuous range of vision at near, intermediate and distance. Symfony utilizes diffractive concentric rings, much like the Tecnis Multifocal (TMF) lens. However, TMF utilizes two foci, and Symfony utilizes one elongated focal point to extend the range of vision. Therefore, if TMF and Symfony IOLs are likened to spectacles, TMF would be like a bifocal and Symfony would be like a progressive lens. Both the TMF and Symfony correct for chromatic aberration by incorporating achromatic technology.
Image: Parkhurst G
In studies published by the manufacturer, patients with Symfony IOLs are able to achieve 20/20 vision at 66 cm (-1.50 D defocus) and greater distances. At 40 cm (-2.50 D defocus) patients achieved acuities of 20/40 or better. TMF patients also achieved 20/20 vision at distance, but visual acuity is highly variable between foci with TMF IOLs.
Optimal acuity (20/20) is obtained only at two foci with the TMF: distance and near (depending on the model). This results in pockets of reduced vision in the intermediate/near distances for all models of TMF: ZKB00 (+2.75 D), ZLB00 (+3.25 D) and ZMB00 (+4.00 D). The ZKB00, ZLB00 and ZMB00 obtain 20/20 near acuity at 50 cm, 42 cm and 33 cm, respectively.
The Symfony IOL has been shown to be more effective in providing smooth acuity at distance to 66 cm with no pockets of blurred vision. This proves to be beneficial for far distance, intermediate and extended reading distances. However, patients with Symfony IOLs have acuity that decreases linearly with decreased working distance starting at 66 cm. At 66 cm, most patients achieve 20/20 acuity, at 50 cm patients have 20/30 acuity, and at 40 cm patients have 20/40 acuity. The benefit of Symfony is that the vision is gradually lost at near working distances, and the patient will not experience jumps in clarity as seen with the TMF IOL.
The Symfony IOL comes in 0.5-D increments ranging from +5.00 D to +34.00 D in both toric and non-toric multifocals. The Symfony toric lenses come in the following five models: ZXT100, ZXT150, ZXT225, ZXT300 and ZXT375 (the three-digit number corresponds to diopters of cylinder in the lens at the IOL plane). All Symfony lenses are biconvex, with a wavefront-designed anterior aspheric surface and a posterior achromatic diffractive surface. Symfony uses UV-blocking hydrophobic acrylic material.
Patient selection
The Symfony IOL is a great option for patients with clear optical systems who would normally qualify for a multifocal IOL. Patients with astigmatism now have a new option to improve vision and would make great candidates for this surgery.
The major advantage of Symfony over TMF is the increased depth-of-focus. There are no added risks or complications with Symfony. However, the historical risks and complications of cataract surgery still apply.
In the initial studies, 97% of patients were satisfied with the Symfony IOL and would have it implanted again. Although vision at near may be decreased with Symfony, patients obtained two more lines of acuity over monofocal IOLs. Most patients with Symfony reported independence from spectacle use. At distance, 100% of patients reported freedom from spectacles, at arm’s length 97% reported spectacle freedom, and at near 87% reported spectacle freedom. While most patients may be satisfied with their vision without spectacles, some patients may still require spectacle correction for reading. A possible resolution could be to use a blended vision approach.
For example, a Symfony IOL could be used in the dominant eye to maintain the best-corrected vision at distance in the dominant eye and a TMF IOL (model based on the patient’s habitual reading distance) in the nondominant eye for near vision. This would provide clear distance vision in both eyes, clear intermediate vision in the dominant eye and clear reading vision in the nondominant eye. Patients who have unsuccessfully tried monovision correction in the past report that dissatisfaction was based on reduced distance vision in one eye. A blended approach could be an excellent way to achieve spectacle freedom in patients who are sensitive to minor decreased acuity at near.
Overall, with the Symfony lens, patients with astigmatism are now eligible for a multifocal IOL.
- References:
- FDA. FDA approves first intraocular lens with extended range of vision for cataract patients. www.fda.gov/newsevents/newsroom/pressannouncements/ucm511446.htm. Posted July 15, 2016. Accessed September 3, 2016.
- Tecnis Symfony IOL. Tecnis IOL. http://www.tecnisiol.com/eu/tecnis-symfony-iol.htm. Accessed September 3, 2016.
- For more information:
- Daniel Mulder is a fourth-year student at the Rosenberg School of Optometry, University of the Incarnate Word. He recently served a rotation with a cataract surgeon who went on to implant one of the first Symfony lenses in the U.S. Mulder can be reached at dmulder@student.uiwtx.edu.
Disclosure: Mulder reported no relevant financial disclosures.
Perspective
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Michael D. DePaolis, OD, FAAO
Fourth-year optometry student Daniel Mulder provides a nice overview of a timely modality. Through his rotation with surgeon Greg Parkhurst, MD, Mr. Mulder gained valuable insights while observing cataract surgery, enabling him to provide our readers with a specific, relevant description of the Tecnis Symfony’s optics as well as patient selection and fitting suggestions.
It’s refreshing to see one of our future optometrists eager to share his unique experiences with cataract surgery with the readers of Primary Care Optometry News, and we thank him for his contribution.
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