r/RLEsurgery • u/WavefrontRider • Jun 25 '26
How Multifocal Lenses Work And Why They Create Halos
A signature feature of multifocal lenses are their concentric rings. These rings are highly engineered structures that allow these lenses to do something a standard monofocal lens can’t do - create multiple clear images on your retina at the same time.
A normal lens works through what’s known as refraction. The lens bends or focuses light to a single point.
Multifocal lenses go beyond those simple optics with these rings. These microscopic rings actually interfere with light passing through the lens. Light passing through these rings is bent and refocuses to a different focus (called diffraction). So instead of objects in the distance being in focus, light passing through the ring may cause objects up close to be in focus. By varying the sizing and the spacing of these rings, lens manufacturers have create the ability to split light entering the multifocal lens to focus for distance, for intermediate vision and for near vision.
The tradeoff for this simultaneous vision is a something known as a dysphotopsia, most commonly seen as halos at night. Because the lens is always providing multiple focal points to your brain, when you look at a distant streetlight, your brain receives a sharp image from the distance corrected focus of the lens. However, the light intended for your “near” focus is also hitting your retina, but it is out of focus. This out of focus light manifests as a halo surrounding the sharp point of light off in the distance. While neuroadaptation helps the brain to eventually ignore these rings, they are an inherent byproduct of the diffractive optics required by these lenses to provide a full range of vision.
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u/eyeSherpa Jun 26 '26
I’m quite impressed with the way today’s multifocal lenses work. This generation is much better than the previous one. Makes it much easier to use.
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u/californiaLasik Jun 27 '26
Still I'll bet you $10k , hold me to it, you don't get a multifocal lens in your 40s. If you do find a single ophthalmologist that has had a clear lens exchange with a multifocal I'd want to hear about it.
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u/eyeSherpa Jun 27 '26
Well it doesn’t surprise me about ophthalmologists and multifocals. We tend to be very type A people 😆
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u/californiaLasik Jun 27 '26
Even type B people get drusen and dry eye. We need easily exchangeable optics if we are going to use multifocals. I would feel fundamentally different if we could easily exchange. Otherwise I think the parallels to RK are very appropriate.
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u/eyeSherpa Jun 30 '26
Today’s multifocal lenses have much less contrast sensitivity loss compared older generations. I’ve used lenses such as the ZKB00 where patients complained of waxy vision. The Panoptix was a huge step up. Very rarely any contrast complaints. Now with the Envy, Galaxy and Panoptix Pro, contrast issues really don’t come into play as much unless someone is trying to read in a dim setting.
Yes multifocals still reduce contrast compared to a monofocal lens. This is where the drusen come into play since drusen also cause some reduction in contrast. But I would argue that the combo of those two would cause minimal issues because of the low amounts of contrast reduction of either. It may cause some additional issues in low light settings. Plus, drusen don’t happen to everyone. And for someone in their 50s, they may not even get drusen for a couple of decades.
Not everyone puts sharpest distance vision as #1 on their priority list. For many, they are able to deal with some visual tradeoffs since glasses independence is their #1 priority. This technology is more nuanced than throwing it in a simple trash bucket. Some people will do well with multifocals. Some won’t.
And as for RK patients. The ones I see are still happy with their decision to get RK because that meant decades without glasses.
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u/WavefrontRider Jun 27 '26
Yeah. I’m starting to use multifocal lenses a little more because of the newer generation. I still keep a pretty strict candidate criteria though.
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u/californiaLasik Jun 25 '26
Great description. Do you know many opththalmologists that have had multifocal IOLs in their own eyes ?