Cataract surgery has evolved from a procedure devised to remove a cloudy lens to one that additionally aims to incorporate refractive solutions. Until recently, emmetropia for distance vision was the main goal, and many patients required reading glasses after surgery. However, improved techniques and increased patient expectations have resulted in the quest for a simultaneous presbyopic solution.
Various multifocal IOL designs have been an excellent option in patients who desire spectacle independence. Specifically, the latest generation of trifocal IOLs provides excellent distance, intermediate, and near vision with high levels of spectacle independence and patient satisfaction. However, several factors can still affect visual results and patient satisfaction. Chief among these are glare and halos and reduced contrast sensitivity. Another is the fixed focusing distances that these lenses afford.
EXTENDED RANGE OF VISION
In June 2014, the Tecnis Symfony IOL (Abbot Medical Optics; Figure 1) received the CE Mark. This IOL offers several advantages over traditional multifocal IOLs. One is its echelette design, which produces a unique pattern of light diffraction, elongating the focusing ability of the eye. The result is an extended range of vision.
Another advantage is that the Symfony compensates for image-degrading chromatic aberration between shorter blue and longer red wavelengths. It has been reported that correction of chromatic aberration results in a sharper focus of light.1,2 This lens design therefore allows improved depth of focus, increased retinal image quality, and reduced visual disturbances (glare and halos) compared with the design of traditional multifocal IOLs.
REAL WORLD RESULTS
My colleagues and I have compared the performance of the Symfony IOL with the AT LISA tri (Carl Zeiss Meditec). We used a standard monofocal IOL (Tecnis; Abbott Medical Optics) as a control. The defocus curve of the control provided a benchmark for the other two groups.
Each lens was implanted in one eye of 10 consecutive patients (20 eyes) who presented for cataract surgery or refractive lens exchange with no other ocular comorbidity. Both the Tecnis Symfony and the AT LISA IOLs performed well and similarly to each other, with all patients achieving 20/25 visual acuity or better and excellent levels of uncorrected near, intermediate, and distance visual acuities (Figure 2; personal data submitted for publication). In terms of the defocus curves, the AT LISA had three distinct points of focus corresponding to near, intermediate, and distance vision, with a drop in vision between these points. By contrast, the Symfony had a smooth defocus curve up to approximately 2.50 D (Figure 3). We also found that the Symfony provided better contrast sensitivity than the AT LISA tri and Tecnis monofocal IOLs (Figure 4).
CONCLUSION
The AT LISA tri and the Symfony IOLs are high-quality lenses that produce excellent near, intermediate, and distance vision. The early results from our small group of patients, however, suggest that the latter provides an extended range of vision. Therefore, we have found that the Symfony IOL offers another option in presbyopia correction with improved contrast sensitivity and reduced glare and halos.
Amir Hamid, BMedSci, FRCOphth, is Medical Director of Ultralase Optimax Eye Surgery Specialists in London. Dr. Hamid states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: amir.hamid@optimax.co.uk.
- Weeber HA, Piers PA. Theoretical performance of intraocular lenses correcting both spherical and chromatic aberration. J Refract Surg. 2012;28(1):48-52.
- Artal P, Manzanera S, Piers P, et al. Visual effect of the combined correction of spherical and longitudinal chromatic aberrations. Opt. Express. 2010;18(2):1637-1648.
