Joel Hunter, MD Refractive Surgeon, Hunter Vision Updated 10/31/18 11:21 AM
The goal of RLE is to allow you to see near and far without needing glasses. That goal is easily met before the age of 40—with glasses and contacts for some or without for others. But after that age, your eye can only do one or the other. It can only see distance, or only see near, but the seamless autofocus between the two is lost forever. And sadly, I actually mean forever with the current technology available. We may come up with a new autofocusing lens or a way to restore autofocus to the natural lens, but we’re not there yet. We’re really not even close; nothing is waiting in the FDA pipeline that’s anywhere near that standard.
So the way we can fix near and distance vision both is by wearing reading glasses or bifocals. If you’re among the majority of folks who don’t like that option, there is another way around it. The way to avoid the need for glasses is to split the light coming into the eyes so that some is focused for distance and some is focused for near. The details on percentages of light focused for each and how much focusing power is necessary are super complicated, but luckily, they’re also unnecessary to understand this topic.
Intra-ocular lens options
There are two ways for an intra-ocular lens (IOL) to split the light entering your eyes into near focus and distance focus. The first is to use concentric rings of near and distance focus and let your macula (the central vision part of your retina) sort it out. This is called a multifocal IOL. The second way is to have one eye of more clarity for distance and the other eye have more clarity for near and let your visual cortex in your brain sort it out. This is called blended vision.
To be a candidate for a multifocal IOL, you need to meet a lot of specific criteria. They’re all centered around the same idea: you must have the potential for excellent contrast sensitivity (image sharpness). That’s because multifocal IOLs reduce contrast sensitivity. It makes sense. With only some of the light being focused whether you’re looking at near or distance, not as much contrast is possible. The best multifocal IOLs decrease contrast the least, but they all reduce it some. That being said, in eyes that are otherwise ideal in the contrast department, multifocal IOLs are an excellent option.
To be a candidate for blended vision, you must have the potential for each eye to see well on its own. That means that after the old lens is out and the IOL is in its place, each eye needs to be able to see 20/20. You’ll notice the pre-operative standards aren’t quite as stringent. That’s because they don’t need to be for blended vision to work. I’m admittedly biased here, although I have used and still use both options for IOLs. It’s just that when I’ve been the “second opinion” doc for patients who aren’t quite where they’d like to be visually, I end up exchanging multifocal IOLs for blended vision IOLs. It’s hard not to get biased after the first few times that happens.
My theory for why this happens is that the visual cortex can sort out blended vision a little easier in those (somewhat rare) cases where a multifocal IOL isn’t allowing enough contrast sensitivity for good vision. There other places I’ve written about blended vision. But since this article is about IOL options, I’ll just point out that it utilizes an aberration-free monofocal IOL.
Either choice can be a good choice
There are a lot of different brand names of IOLs, but they all boil down to these two options: multifocal or monofocal. (A quick extra point about a third IOL type—I used Crystalens many, many times and I don’t have nice things to say about it so I won’t say anything because that’s what I was told to do by my mother.) Either choice can be better depending on what your pre-operative diagnostics show. The good news is that with all the choices, most people can be a candidate at some point for one or the other.