Which multifocal lens is best? A question I am often asked by patients. With different eye clinics advertising and claiming that the lens they offer is better than anything else, potential patients wishing to have cataract surgery or refractive lens exchange (RLE) surgery can be faced with a confusion of choice.
Multifocal lenses are a type of intraocular lens implanted at the time of lens surgery (cataract or RLE). They differ from standard monofocal lenses, which generally give good distance vision in that they offer the opportunity for patients to enjoy a range of vision from distance, intermediate and near without the need for glasses. This is achieved by an lens optical design which typically consists of concentric rings of increasing power separated into seamless zones for vision at a range of distance. This is an attractive proposition for someone who wants to be independent of glasses for distance and in particular reading vision. My patients often say they feel younger after multifocal lens surgery because they aren’t shackled to reading glasses any longer.
To understand what some of the different lenses offer it is important to understand the very basics of optics. Someone wishing to read at 40cm ( a typical distance of a book or newspaper) would usually require additional optical power of +3.0 dioptres (unit of power). On the other hand if the text was held at arm's length (intermediate distance) the optical power required would be roughly +1.5 D. Seeing in the distance doesn’t require any additional optical power over what is required to correct distance vision in that individual. Having understood these basics it is possible to explain what the current lenses offer and move closer to the answer to the question on which multifocal is better.
Amongst the current crops of multifocal lenses the predominantly used lenses are the Physiol Finevision Trifocal lens, Zeiss AT-LISA trifocal lens and the AMO Symfony lens. Both the Physiol Trifocal and the Zeiss Trifocal have built in powers of 1.75D for intermediate and 3.5D for near, giving a full range of vision at all distances. The Symfony lens has an intermediate only power of +1.75D. Other lenses such as the Oculentis Mplus Comfort or Mplus MF20 have powers of +1.5 and +2.0D respectively. Surgeons using Symfony or Mplus lenses typically ‘extend’ the range of focus of these lenses by targeting the patient’s non-dominant eye for a small amount of added prescription (0.5 to 0.75D) to boost the range of focus in one eye (technically called micro-monovision).
In term of post-operative results, a higher proportion of patients are completely independent of glasses after trifocal lenses than they are with other types of lenses. This is down to the simple fact that the optics of these lenses (the +3.5D part) allow reading at 40cm. Having said that, this doesn't mean the other lens designs aren’t as good. The right lens depends on each patients lifestyle and visual needs. The person who likes playing golf, doesn’t read that much and doesn’t mind the possibility of occasional glasses would be very happy with a Symfony or Mplus lens. A bookworm who loves reading or someone who loves sewing would probably prefer a trifocal lens.
Patients should be aware of some other factors with multifocals. All multifocals can cause glare and haloes around bright point sources of light such as headlights when driving at night. This tends to be more common with trifocal type lenses and occur less often with the Symfony or Mplus lenses. In the majority of cases even where there are haloes around headlights when driving at night patients are so delighted with their new independence from glasses that they don’t find the haloes particularly troublesome. Personally I haven’t had to remove any lenses in patients due to night time haloes. Some patient may just never like the quality of vision they achieve with a multifocal lens and roughly 0.5% of my own patients require an exchange of lens implants due to dissatisfaction. This can be with any type of lens. The final thing to mention is that multifocal lenses of all types work best in good lighting. Hence a patient with a mutlifocal trying to read the program at the theatre or opera with the lights down can struggle.
Which is the best type of mutlifocal lens? Trifocal or Symfony? The answer depends on your lifestyle and needs. If you’re an outdoor sportsman who reads on an Ipad and doesn’t mind the possibility of occasional reading glasses, the Symfony lens may suit you. Alternatively, if you're a book worm and hate the idea of reading glasses, one of the Trifocal lenses may be best for you. If your’e a taxi driver that drives at night for work the Symfony or Mplus lens may be the best option for you with occasional use of reading glasses.
I would also advise you to follow the advice of your eye surgeon. Surgeons like me that do this type of lens surgery tend to stick with lenses we know work and keep our patients happy. Each surgeon will have their own preferences, but be assured that these preferences are based on the knowledge of satisfaction from past patients. I personally use the Finevision, Zeiss and Symfony lenses.
Finally, my old mum just had lens surgery. She’s 72, a retired psychiatrist who reads a lot, sews for her grand kids and plays golf twice a week. She had the Zeiss trifocal lens. She’s over the moon!
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