Joel Hunter, MD Refractive Surgeon, Hunter Vision Updated 07/03/19 5:06 PM
The meanings of “nearsighted” and “farsighted” can be confusing. Once we define farsightedness, we can discuss if LASIK might help. Ok?
Definitions of Farsightedness and Nearsightedness
The terms “nearsighted” and “farsighted” have become common terms to describe vision problems that are technically referred to as “myopic” and “hyperopic,” respectively. This is an odd development, because it’s common for simpler, clearer explanations to take root in our lexicon. But in this case, half the time people say “nearsighted” or “farsighted,” the definitions get mixed up. I notice this because most of the people I meet every day happen to be talking about their vision. When they get to the word “nearsighted” it usually sounds like there’s a question mark after it. “I can’t see anything because I’m so… nearsighted?” I used to have this problem, too. Short of becoming an ophthalmologist, nothing could keep it straight for me. In our defense, it is confusing that “farsighted” means you can see far away. Every other time we use words in this manner, we’re usually referring to something that isn’t functioning. Gastritis? Bad stomach. Laryngitis? Bad larynx. Farsightedness? Great far vision. People have good reason to feel uncertain about how to describe their vision.
A note to the NEARsighted
It’s possible you may have stumbled on this article while trying to find a solution to your blurry distance vision. (This means you have nearsightedness on account of your functional near vision). If that’s you, I can tell you from the start that LASIK usually can help. But if it’s farsightedness you have, the answer is somewhat more involved.
How to know if you’re farsighted, and what it really means
The easiest way to know if you’re farsighted is to take a look at your glasses’ or contacts’ prescription. What you’re looking for is the “+” or “-” in front of your prescription. The number doesn’t matter for this. If what you see is a plus sign, then you’re very likely farsighted. And that plus sign? That’s there for the same reason the answer to the question “Can LASIK help farsightedness?” is more involved.
If you're the type that wonders "Can I have LASIK eye surgery for farsightedness?" you've come to the right place.
Before I annoy some folks by accident, here’s a spoiler. This is for those who’ve run out of patience and find the nuance in this explanation tedious instead of enthralling (or, at the very least, interesting). LASIK can sometimes fix farsightedness (hyperopia) with great accuracy and results. But this is only if your eye has some specific criteria determined during evaluation.
Back to the plus sign. The plus is there because your eye needs to have some focusing power added to it to have clear vision. It’s the reason farsightedness can sometimes take years to cause any trouble with the vision. The natural lens inside your eye has a built-in autofocus that happens to specialize in one thing: adding focusing power. That feature is there for one main purpose, which is to allow clear near vision.
Have you ever seen a camera’s viewfinder display snap into focus after a split second of blur, as you point at something a few inches from the lens? If so, you’ve seen the reason we need autofocus in our eyes. You need more focusing power added for up close vision to be clear. With farsighted eyes, there’s not enough focusing power to see a clear image anywhere, near or far. But that autofocusing lens inside the eye comes to the rescue because it can add the missing power. Who cares if that’s supposed to be reserved for reading? “I’ll give my power to help you focus wherever you need,” is how the lens responds to the need of the farsighted human.
In all honesty, the lens in your eye is a lot like The Giving Tree. But there comes a day when the lens is older, stiffened from the passing years, and it has no more power to give. In those final days, with a bit of straining, it gives its last bit of focusing power to let you see. A pair of glasses will need to add that power for you from now on. That first pair of glasses has a plus sign in front of the prescription, representing the focusing power they will add. Now that we’re all crying, (No? Just me? Well then everyone’s heart must be harder than the lens in that story.) we can now discuss how LASIK can help in some cases.
LASIK can help farsightedness—but it’s not for everyone
LASIK is outstanding at one thing. It takes the prescription you need in your glasses or contacts and puts it on the front of your eye. From then on, your vision is always corrected no matter where you focus. In the case of a plus prescription—when the lens inside the eye has given all the power it can—LASIK can add that power to the eye. The changes it must make to the topography of the cornea are more complex than for nearsighted LASIK, and the requirements are more exacting. Since the cornea must become steeper—a hill instead of a plain—its topography has to start out as just that. It must be a plain with no interesting hills or valleys. While LASIK can make the cornea steeper when those conditions are met, it must not be made too steep or the quality of vision won’t be optimal.
If your plus prescription is high or your cornea already has a somewhat steep curvature to begin with, it is important you go to an excellent LASIK surgeon. This is because a good surgeon will be honest and helpful by telling you that you shouldn’t get LASIK. A consult with a surgeon like that will let you know if LASIK could add the focusing power to your eyes that your natural lens once did. In those cases, I’d like to think it makes the old lens happy to have the eye focused again like in the bygone days. As an added bonus, it’s nice to not have to keep track of whether it’s farsightedness or nearsightedness you’ve got, because you no longer have to deal with either.
Why is there less of a chance for LASIK if I’m farsighted?
I wish it was a myth that the chance of LASIK candidacy is lower for folks who are farsighted. I wish I could say, “Good news! LASIK is almost always amazing for people who are farsighted!” But I can’t say that. It isn’t a myth. It’s just science that determines the decreased chances for LASIK if you’re farsighted. And as I learned during my demoralizing attempts to build a hoverboard as a child, science doesn’t care about my hopes and dreams.
We know the reason it’s harder to be a candidate for LASIK if you’re hyperopic (if we’re talking science, it seems like we should use the official language for farsightedness). LASIK works by changing the shape of the clear, domed window on the front of your eye called the cornea. The excimer laser used in LASIK is able to sculpt that cornea with extreme precision without damaging tissue that we don’t want to sculpt. The keyword, however, when we’re describing the difference with hyperopic LASIK isn’t precision; the keyword is sculpt.
Myopic vs. Hyperopic LASIK
The laser (and any other technology, for that matter) can’t change the shape of the cornea by adding anything to the shape. It can only sculpt — that is subtract — to make the shape into what you’d need to have clear vision. With myopic LASIK, that’s easy to describe: the cornea is too steep to see clearly so it is made more flat. That’s a situation set up perfectly for subtraction. With hyperopic LASIK, we’ve got the opposite issue. The cornea is too flat to see clearly and must be made steeper. But we can’t add to the hilltop. How would we make it steeper?
The answer is in sculpting down the sides of the hill to make everything more steep. Part of why LASIK used to be a non-starter altogether for hyperopes is that the algorithms for driving the laser weren’t sophisticated enough to treat only the periphery and leave the center alone. It could treat hilltops, but didn’t do a good job of treating anywhere else. Then LASIK got better and could be done on hyperopes, but not very well. The regression effect (“my LASIK wore off”) was really terrible because the laser could basically sculpt a moat around the center of the cornea. Now, with modern laser, there are very good hyperopic treatments that are able to smooth down the periphery and steepen the cornea much more naturally. At last, people who are hyperopic have a LASIK option.
I am hyperopic (farsighted). What are my chances?
The chances of being a hyperopic candidate, however, are still much lower than if you are myopic. That’s because the way the prescription is fixed has become unimaginably more precise, but relies on the same principle of sculpting that it always did. We still can only smooth down the sides of the hill. As hyperopic prescriptions get higher (usually around +2.00 or above) the amount of sculpting in the periphery necessary becomes problematic. The hilltop — the center of the cornea — remains untouched but the more we steepen the hill, the smaller the hilltop becomes.
That center of the cornea is the optical zone you’re looking through for clear vision, so as you’d assume, a large optical zone matters. If the “treated” optical zone (even though laser never touched it) is made too small, then you’ll end up with problems we used to see in the old days of LASIK. The chances increase of night vision trouble, lack of clarity, halos, etc. So while it is a near certainty of having 20/20 distance vision and reading vision without glasses, the cost to the quality of your vision isn’t worth it. There is such a thing as a bad 20/20.
With the imaging diagnostics available today, and our understanding of how corneal topography influences vision, we can make the right choice ahead of time. We don’t have to go into LASIK wondering how it will turn out. That’s great news for LASIK candidates and non-candidates alike, because having eyes that see clearly without glasses is amazing, but having eyes that are able to see clearly with or without glasses is even more important. There are cases where hyperopic LASIK is fantastic, and you get to have both: clear vision and no glasses. But when you’re farsighted and LASIK isn’t an option, you can take comfort in knowing you’re probably going to have options that are even better to get out of glasses — either in the future or right now.