Multifocal IOLs were an immediate game-changer when they arrived on the scene in the late 80s. Distance and near vision through the same lens? We couldn’t believe it. I was six at the time, but I bet I had a good day without even realizing why.
What they do and how they work
Since then, the technology has continued to improve and multifocal IOLs have become such a hot topic that just one blog won’t do it. We’ll need at least 10 blogs to – wait, no, come back, okay yes 10 is too many, I see that now – at least 2 blogs to get the job done. So today, we begin with what they do and how they work. This will be followed by this blog’s annoying younger brother, “What they don’t do and why not.”
In an earlier blog, we talked about how the natural aging of the lens changes our eye from “autofocus” into “fixed focus” mode. Ideally, we could just replace your fixed focus (worse) natural lens with a new one that has autofocus (best). Sadly, that technology doesn’t exist; and as of the time of this writing, it isn’t even on the horizon. Instead, we can replace your fixed focus (worse) natural lens with a new one that is multifocal (much better).
By “much better,” I’m referring to the ability to read and see distance both without requiring a pair of glasses. A multifocal lens has rings of near and distance-focused power like an archery target. That way, you’ve got focused light if you’re reading a book, and if you look up across the room, you’ve still got focused light.
Is this lens focused for distance or near?
It doesn’t work by changing focus from distance to near (like the autofocusing lens your eye had from birth till somewhere in your forties). It works by sharing focus for distance and near. With a natural, youthful autofocusing lens, or with a monofocal IOL, you could ask, “Is this lens focused for distance or near?” And you’d be able to get a straight answer. With a multifocal IOL, if you ask, “Is this lens focused for distance or near?” the answer will be, “Yes.”
This used to be (in the 90s) a somewhat blunt, ham-handed solution because the light coming into the eye was split into distance and near in an extreme way. The result? Big ol’ halos and a lack of sharpness to the vision whenever it was even mildly dim (dusk, dawn, indoors… lots of places). Nowadays, multifocal IOLs are much more advanced. But “advanced” is a generic, brochure buzzword kind of adjective, so what does that actually mean?
Modern Multifocal Technology
Modern multifocal IOLs work better because the aberrations (that steal away sharpness and clarity) are dramatically reduced. There is precision to the split – the sharing – of light being focused at distance and near. The science behind it is super impressive (and impossible to explain in-depth without 10 hours, 4 cups of coffee, and 2 whiteboards). The less in-depth (but still accurate) description is that the multifocal rings diffract (spray) and refract (bend) the light coming into the eye in a precise way; a way to create the least amount of halo and more sharpness to the image. In addition, your pupil is different in size when looking near vs. far – a feature modern multifocal technology uses to your advantage.
The take-home is that modern multifocal IOLs can be perfect for people that follow into the middle of a Venn diagram with two qualifiers. The left circle is non-negotiable from the clinical perspective. The right circle is non-negotiable from the patient perspective. A “great candidate” means that the anatomy and physiology of the eye should allow excellent near and distance vision without glasses, with minimal side effects. Advanced 3D imaging and diagnostic testing determines this.
For the circle on the right, there are some folks – and some jobs – that require both eyes to have the exact same vision without glasses. You might be one of those people. The best way to determine if you are is in consultation with your doctor.
The “multifocal sweet spot”
When people fall into the “multifocal sweet spot,” it can feel miraculous. Both eyes can see distance, and both eyes can see near. It’s worth finding out if you’re a candidate, because we have options for multifocal IOLs now that allow for clarity that was impossible just a few years ago. It’s possible to have vision that just… works, where you never have to think about glasses again because everything is just clear all the time.
It’s also worth finding out because sometimes there’s a better option than a multifocal. And even though I hate a cliffhanger as much as the next guy, that’s what we’ll discuss in Part Two.