Presbyopia is defined as a progressively diminished ability to focus on near objects. It is derived from the Greek word presbys, which literally means ‘trying to see as old men do’.
Traditionally it has been managed with a spectacle correction with either near addition glasses (readers), bifocal or varifocal spectacles. More recently the use of multifocal contact lenses has gained popularity.
Surgical management
For those in search of reduced spectacle or contact lens dependence (or complete independence), several surgical techniques have been introduced. These include corneal laser vision correction (monovision or multifocal corneas), corneal inlays and refractive lens exchange (RLE) employing the implantation of a multifocal intraocular lens. The choice of treatment depends on an individual’s lifestyle, visual demands, budget and the availability of surgical expertise and instrumentation.
Refractive lens exchange with intraocular lens implants
RLE is identical to the cataract extraction and implantation of lens implants performed routinely in the NHS. Modern cataract surgery has proved to be extremely effective and safe with a very low rate of complications.1 As such, attention has increasingly turned to using this technique in clear lens extraction for presbyopic individuals. The difference is that instead of implantation of a monofocal intraocular lens, giving only good uncorrected distance or near vision, a bifocal or trifocal lens is used. This presbyopic ‘refractive lens exchange’ has proved to be a safe and effective method for reduced spectacle dependence.2,3 Furthermore, it has the added attractiveness of being a definitive procedure with no further interventions required in later life.
Multifocal lenses have been an excellent option in such patients. The latest generation of trifocal intraocular lenses allow excellent levels of distance, intermediate and near vision with high levels of spectacle independence and patient satisfaction.3,4 Despite this, there are several factors which can affect visual results and patient satisfaction. Chief among these are glare and haloes, and reduced contrast sensitivity. Another is the fixed focusing distances such lenses afford.
The Symfony IOL: extended range of vision vs multifocality
In June 2014, the Tecnis Symfony IOL (Abbot Medical Optics, Santa Ana, California, USA) received CE marking. This new IOL offers several exciting new advantages over traditional multifocal IOLs.
The Symfony uses an ‘echelette’ design which produces a unique pattern of light diffraction. This elongates the focusing ability of the eye and allows an extended range of vision. The Symfony also compensates for chromatic aberration between shorter blue and longer red wavelengths, which can lead to image degradation. It has been reported that correction of chromatic aberration results in a sharper focus of light.5,6 This allows for improved depth of focus, increased retinal image quality and reduced visual disturbances (glare and haloes).
Early results
We have previously reported on our results in a small pilot study.7,8 In this study we were able to demonstrate a smooth extended range of vision in the Symfony group of patients versus three points of focus in a trifocal IOL (AT Lisa Trifocal Carl Zeiss Meditec) group representing near, intermediate and distance vision (Figure 1).
We were able to defocus the Symfony by up to 1.5D with no significant reduction in visual acuity. Binocular uncorrected visual acuity was 20/25 or better in 90 per cent of the Symfony group and 92 per cent in the trifocal group (Figure 2) with the Symfony group achieving binocular uncorrected near vision of N6 or better in 82 per cent of patients and N6 or better in the trifocal group in 74 per cent of patients.
The Symfony IOL also demonstrated higher levels of contrast sensitivity compared to both the AT Lisa trifocal group and a control group comprising patients with implantation of the Tecnis monofocal IOL (Figure 3). This is consistent with AMOs own trial data.9,10
Recently we have been able analyse the results of 95 consecutive eyes implanted with the Symfony IOL and 98 consecutive eyes implanted with the AT Lisa trifocal IOL. Visual performance at three months postoperatively for both groups were excellent with the Symfony group achieving binocular uncorrected visual acuities (BUCVA) of 20/25 or better in 96 per cent of patients and in the trifocal group this was 94 per cent (Figure 4).
Near visual acuity was N6 or better in 78 per cent of patients in the Symfony group and 81 per cent in the trifocal group, N5 or better in 63 per cent of the Symfony group and 60 per cent in the trifocal group (Figure 5).
Conclusion
Both the AT Lisa and the Symfony are high quality lenses, which produce excellent results. These results from a larger group of patients with longer follow up than in our previous study allow cataract and refractive surgeons another option in presbyopia correction with the Symfony IOL. It offers an extended range of vision, improved contrast sensitivity and reduced glare and haloes.
References
1 Narendran et al. Eye (2009) 23, 31-37; doi10.1038/sj.eye.6703049
3 Hamid et al. Efficacy and rotational stability of the AT Lisa Trifocal Toric IOL.
4 Mojzis P et al. J Refract Surg, 2014, Oct;30(10):666-72. doi: 10.3928/1081597X-20140903-06.
5 H.A Weeber and P.A. Piers. J Refract Surg, 2012;28(1):48-52.
6 P. Artal et al. Optics Express, 2010; 18(2):1637-1648.
8 Hamid A. Cataract and Refractive Surgery Today Europe. October 2014, 36–37.
9 AMO: 168 Data on File_Symfony_Simulated Defocus Curves
10 AMO: 166 Data on File_Extended Range of Vision IOL 3-Month Study Results (NZ)
Amir Hamid is consultant ophthalmic surgeon at North East London Treatment Centre, King George Hospital, Ilford, and medical director at Optimax and Ultralase, UK. Arif Sokwala is head optometrist at Optimax and Ultralase