Just as cataract surgery and IOL technology are rapidly advancing, so too are patients’ demands for their vision. The loss of accommodation after cataract surgery has been an inconvenience to patients for several decades and is often corrected with near-vision spectacles. However, with many patients now desiring complete spectacle independence, a growing focus has been placed on presbyopia-correcting IOLs. As a result, numerous lenses have been developed to address this condition.
One of the earliest types of presbyopia-correcting IOLs were accommodating IOLs, which are designed and positioned within the capsular bag in such a way that they change shape as the ciliary body contracts, thus mimicking the natural accommodation of the lens. The FDA trials of these lenses showed promising results, with nearly 100% of patients attaining 20/40 or better distance, intermediate, and near BCVA.1 Patients are typically happy with the intermediate vision provided by these lenses, but studies have found that these IOLs do not offer the accommodative range necessary for near work2 and are prone to lens tilt and decentration once capsular fibrosis sets in.3 Prophylactic Nd:YAG laser capsulotomy can help prevent this complication. Multifocal IOLs, which focus images at two or three focal planes, are now more commonly used to correct presbyopia.
Both refractive and diffractive multifocal IOLs are available, with varying degrees of add power built into the lenses. The discrete focal points of these lenses allow for more reliable distance and near targeting. Common complaints associated with multifocal IOLs are glare, halos, and decreased contrast sensitivity4,5; however, patients implanted with the newer low-add multifocal IOLs have fewer complaints of these issues. A more recent addition to the armamentarium of IOL technology is the so-called extended depth of focus, or EDOF, IOL, which aims to optimize visual acuity at intermediate distances without compromising distance vision. In July 2016, the first EDOF lens—the Tecnis Symfony (Abbott Medical Optics [AMO])—was approved by the FDA for use in the United States. This article focuses on both low-add diffractive multifocal IOLs and the Symfony IOL.
LOW-ADD DIFFRACTIVE MULTIFOCAL IOLs
The main diffractive multifocal IOLs used today in the United States are the Tecnis (AMO) and AcrySof IQ ReSTOR (Alcon). These IOLs use apodized diffractive surfaces to focus light at two focal planes, thus achieving good uncorrected near visual acuity (UNVA) and uncorrected distance visual acuity (UDVA). Initially, these IOLs had high add powers built in, such as the SN6AD1 (Alcon; +3.00 D), SN6AD3 (Alcon; +4.00 D), and ZMB00 (AMO; +4.00 D). The postoperative outcomes achieved with these lenses are good, with Chiam et al6 reporting UDVA of 20/30 or better in 93% of patients and UNVA of 20/30 or better in 75% of patients implanted with the SN6AD3. Similar results have been reported with the ZMB00.7Unfortunately, while UDVA and UNVA are excellent, uncorrected intermediate visual acuity (UIVA) with these lenses is suboptimal.8
To address this issue, low-add IOLs were developed, including the SV25T0 (+2.50 D [Alcon]), ZKB00 (+2.750 D [AMO]), and ZLB00 (+3.25 D [AMO]). These lenses have a shorter distance between focal planes, thereby improving visual acuity along the defocus curve. The postoperative outcomes with low-add IOLs are promising.9-12 Hayashi et al9 compared visual acuity results achieved with a monofocal IOL versus the SV25T0. The investigators found that both IOLs performed comparably for UDVA, while the SV25T0 performed significantly better for UNVA (30 cm) and UIVA (50 cm). Glare and contrast sensitivity were comparable for both IOLs, although halos were more commonly reported with the SV25T0. Similarly, Kretz et al11,12 studied ZKB00 and ZLB00 outcomes and found that 100% of patients were at least moderately happy with their postoperative results, and only 15.3% (ZKB00) and 13.6% (ZLB00) required spectacles for some daily activities.
It is clear that low-add multifocal IOLs produce good results, but how do they stack up against high-add multifocal IOLs? In a world where computer and cell phone usage—with a working distance of 40 cm to 60 cm—are becoming more prevalent, having optimal intermediate vision is becoming increasingly important. Kim et al13 compared outcomes of patients implanted with the ZKB00, ZLB00, and ZMB00 in a prospective study. As expected, UDVA was comparable for all IOLs, while the high-add lens performed significantly better at 33 cm (0.17, 0.13, and 0.11 logMAR for the ZKB00, ZLB00, and ZMB00, respectively) and the low-add lenses performed significantly better at 50 cm (0.10, 0.14, and 0.18 logMAR for the ZKB00, ZLB00, and ZMB00, respectively). Although glare and halo symptoms were not significantly different among the lenses, patients were subjectively more satisfied with the low-add lenses.12 Studies evaluating the ReStor lenses have yielded similar results.14,15
Mastropasqua et al14 compared outcomes of patients bilaterally implanted with the SV25T0, the SN6AD1, or a combination of the two. Unsurprisingly, the SN6AD1 performed better at 30 cm to 40 cm, and the SV25T0 performed better at 60 cm. The combination group had a wider range of spectacle independence at all distances, suggesting that combining low-add and high-add multifocal IOLs could be a viable solution for achieving optimal vision for all daily activities. Although low-add diffractive multifocal IOLs produce excellent vision over a wide range, patients can still experience the side effects of multifocality, including glare, halos, and decreased contrast sensitivity. In the aforementioned study by Kim et al,13 despite the satisfaction reported by patients implanted with low-add multifocal IOLs, 30% to 50% still experienced halos and glare.
SYMFONY LENS
The Tecnis Symfony EDOF IOL has been in use in Europe since 2014, but with its recent FDA approval, it stands to be a large player in the US market. The Symfony lens utilizes proprietary diffractive optics to extend the range of vision and is designed to minimize spherical and chromatic aberration, thus achieving satisfactory distance, intermediate, and near visual acuity while decreasing the risk of glare and halos. A toric version is also available, increasing the number of patients that can have this lens.
International studies of the Symfony IOL have confirmed that the lens provides excellent near and intermediate vision.16,17 A multicenter trial in New Zealand showed that patients with the Symfony IOL experienced 20/20 or better mean UCVA from distance through 1.50 D of defocus and 20/40 or better through 2.50 D of defocus.18 In the US multicenter trial that ultimately led to its FDA approval, patients bilaterally implanted with the Symfony IOL were compared with those implanted with the Tecnis monofocal IOL. Patients in both groups had similar UDVA results, but those in the Symfony group achieved 1.7 more lines of intermediate (66 cm) vision and 2.2 more lines of near vision. The mean UNVA for the Symfony group was between 20/25 and 20/30.19 Notably, in both studies, there was no difference in the rates of glare and halos between the Symfony and monofocal groups. Head-to-head studies are still needed to compare the Symfony IOL with low-add diffractive multifocal IOLs in regard to vision along the defocus curve and visual side effects.
CONCLUSION
Presbyopia-correcting IOLs have made great strides over the past 2 decades. Both low-add diffractive multifocal IOLs and the newly approved Symfony EDOF IOL have allowed patients to achieve spectacle independence over a long range of vision, with decreasing side effects. Presbyopia still remains an ever-present challenge without a perfect solution, but these lenses are undoubtedly a step in the right direction.
1. Cumming S, Colvard DM, Dell SJ, et al. Clinical evaluation of the Crystalens AT-45 accommodating intraocular lens: results of the U.S. Food and Drug Administration clinical trial. J Cataract Refract Surg. 2006;32:812-825.
2. Stachs O, Schneider H, Beck R, Guthoff R. Pharmacological-induced haptic changes and the accommodative performance in patients with the AT-45 accommodative IOL. J Refract Surg. 2006;22:145-150.
3. Cazal J, Lavin-Dapena C, Marin J, Verges C. Accommodative intraocular lens tilting. Am J Ophthalmol. 2005;140:341-344.
4. Davison JA, Simpson MJ. History and development of the apodized diffractive intraocular lens. J Cataract Refract Surg. 2006;32:849-858.
5. De Vries NE, Webers CAB, Touwslager WRH, et al. Dissatisfaction after implantation of multifocal intraocular lenses. J Cataract Refract Surg. 2011;37:859-865.
6. Chiam PJ, Chan JH, Aggarwal RK, Kasaby S. ReSTOR intraocular lens implantation in cataract surgery: quality of vision. J Cataract Refract Surg. 2006;32:1459-1463.
7. Akaishi L, Vaz R, Vilella G, et al. Visual performance of Tecnis ZM900 diffractive multifocal IOL after 2500 implants: a 3-year follow up. J Ophthalmol. 2010;2010. pii:717591.
8. Petermeier K, Messias A, Gekeler F, et al. Outcomes of the Acrysof ReSTOR IOL in myopes, emmetropes, and hyperopes. J Refract Surg. 2009;25:1103-1109.
9. Hayashi K, Ogawa S, Manabe S, et al. Visual outcomes in eyes with a distance-dominant diffractive multifocal intraocular lens with low near addition power. Br J Ophthalmol. 2015;99(11):1466-1470.
10. Boujan A, Tandogan T, Pinelli G, et al. Clinical results after implantation of a new diffractive, multifocal intraocular lens with a reduced near add power (+2.75D). Klin Monbl Augenheilkd. 2016;233(5):633-638.
11. Kretz FT, Gerl M, Gerl R, et al. Clinical evaluation of a new pupil independent diffractive multifocal intraocular lens with a +2.75D near addition: a European multicenter study. Br J Ophthalmol. 2015;99(12):1655-1659.
12. Kretz FT, Koss MJ, Auffarth GU, et al. Intermediate and near visual acuity of an aspheric, bifocal, diffractive multifocal intraocular lens with +3.25 D near addition. J Refract Surg. 2015;31(5):295-299.
13. Kim JS, Jung JW, Lee JM, et al. Clinical outcomes following implantation of diffractive multifocal intraocular lenses with varying add powers. Am J Ophthalmol. 2015;160:702-709.
14. Mastropasqua R, Pedrotti E, Passilongo M, et al. Long-term visual function and patient satisfaction after bilateral implantation and combination of two similar multifocal IOLs. J Refract Surg. 2015;31(5):308-314.
15. Pedrotti E, Mastropasqua R, Passilongo M, et al. Comparison of two multifocal intraocular lens designs that differ only in near add. J Refract Surg. 2014;30(11):754-760.
16. Pedrotti E, Bruni E, Bonacci E, et al. Comparative analysis of the clinical outcomes with a monofocal and an extended range of vision intraocular lens. J Refract Surg. 2016;32(7):436-442.
17. Kaymak H, Hohn F, Breyer DR, et al. Functional results 3 months after implantation of an “extended range of vision” intraocular lens. Klin Monbl Augenheilkd. 2016;233(8):923-927.
18. Tecnis Symfony IOL. Abbott. https://www.tecnisiol.com/eu/tecnis-symfony-iol.htm. Accessed September 1, 2016.
19. Abbott announces positive results from pivotal study of Tecnis Symfony IOL for cataract surgery. Abbott. May 8, 2016. http://abbott.mediaroom.com/2016-05-08-Abbott-Announces-Positive-Results-from-Pivotal-Study-of-Tecnis-Symfony-IOL-for-Cataract-Surgery. Accessed September 1, 2016.
