Why Does Lasik Wear Off For Some
Lasik permanently changes the cornea. Thus, it lasts forever right? Yes and no. Of course, the answer isn’t as cut and dry as that. That would be too easy! But in reality, many different things determine whether the lasik will wear off.
For the majority of people, lasik will provide great distance vision as long as the eyes remain healthy. The re-treatment rate after today's modern lasik is less than 0.5%. But years out from lasik, it is possible that the eye can change and wear off some of the lasik treatment.
Technology, experience and improvements in surgical technique have greatly improved the way lasik treatments are performed today. Despite all that, there are a few different categories of patients who have an increased risk of lasik wearing off over time. In addition, getting older does change our eye and this will effect how lasik corrects your vision.
What Causes Lasik To Wear Off?
There are a few different ways you have can prescription return after lasik.
Before lasik, your cornea exists in a certain shape. While this shape may not correct your vision well (which is why you need glasses), this shape still exists in harmony with the rest of your eye.
To correct your vision with lasik, we change the shape of your cornea.
For someone who is nearsighted, the cornea is too steep. So lasik works to correct this by flattening the center of the cornea (see also How Does Lasik Work?).
Having a flatter cornea corrects your vision (which is what we want after lasik). But this brings your cornea out of its natural harmony and your own cornea may try to change that.
During lasik, cornea tissue is removed. The cornea can’t regenerate that tissue. But on the surface of the cornea is a thin layer of cells called epithelium similar to the skin that we have elsewhere on our body. These cells are constantly growing.
These cells can actually change the steepness of the cornea to some degree. Over the course of a few months, this layer of cells can become thicker within the center treated part of the cornea; attempting to bring your cornea back into its natural shape. This can cause the prescription to wear off or regress a small amount. Higher treatments, with a greater change, are at a greater risk of this regression.
Change in cornea strength profile
Lasik not only flattens the cornea but causes some thinning to the cornea as well. This can change the strength profile of the cornea.
Imagine you are trying to bend a metal rod for some reason.
- If you have a very thick rod, you need herculean strength in order to bed the rod. The rod will resist your bending.
- Now let’s take a coat hanger. Hopefully you will be able to bend this metal rod.
As the thickness of the rod decreases, it becomes easier to bend.
The cornea has a natural bend in it. That’s how it forms that dome shape. In simple terms, if you make the cornea thinner, you reduce the biomechanics of the cornea and it can bend more. While not as extreme as the metal rod example, this slight change in bend can cause the cornea to become steeper and cause a little bit of regression after lasik.
How Common Does Lasik Wear Off
Despite all those different factors playing a role in causing regression, re-treatments are uncommon after lasik.
The chance of you having residual prescription and needing a re-treatment is 0.5% or less with today’s nearsighted lasik treatments. That’s quite low! Put another way, 199 out of 200 people won’t need a re-treatment after lasik!
And in fact, certain people will likely have an even lower rate.
- Younger patients are less likely to need re-treatments than older patients. (will get to this later)
- Having less prescription and lower astigmatism
- And starting out with a cornea that isn’t so steep
But My Friend’s Lasik Didn’t Last…
Let’s take a walk down history lane.
Lasik received official FDA approval in 1996. Since that time, millions of people have had lasik within the past 2+ decades.
Now, think about how life was like back in 1996. There were no cell phones; the internet was still pretty new. Technology was very different. Even with all that, lasik provided a revolutionary way to correct vision.
But if you're thinking that lasik technology peaked in 1996, you would be dead wrong. Lasik technology has dramatically evolved over the course of those 2+ decades. This improved technology has led to improved outcomes.
Older lasik treatments had a higher re-treatment rate. In fact, this rate could be as high as 10-15%. Gradually this number came down to the number we see today. What led to all the change?
The laser technology behind lasik is one major component of the re-treatment rate. As mentioned above, lasik works by flattening the center of the cornea. The center of the cornea, after-all, is the part of the cornea in which we look out of to see. And this is what old-style conventional lasik treatments did. They treated the center of the cornea.
Conventional treatments, however, caused a greater slope difference between the center treated cornea and the peripheral untreated cornea. This can increase regression. (as well as cause extra halos around lights at night).
This led to the development of wavefront-optimized lasik in 2003. This particular type of treatment created a blended transition zone between the treated and the peripheral cornea. This prevented sharp differences in the cornea to improve outcomes and reduce the chance of regression.
Change in patient selection
Back in the early days, lasik was used to treat very high prescriptions. If you remember from above, high treatments lead to higher regression and re-treatment rates. But as vision corrective surgery progressed, less and less of these patients with high prescriptions were getting lasik.
Instead of lasik, a different procedure emerged to correct these high prescriptions. In 2005, the Visian ICL received FDA approval. This procedure differs from lasik in that it uses a tiny lens placed within the eye to correct vision (see also Learn Exactly What Is ICL Surgery). Because this lens is able to be manufactured in many different powers, it allows ICL to correct a very large range of vision. And the ICL became the preferred option for those with very high prescriptions.
Change in surgeon experience
Technology and patient selection can explain a large amount of the improvements in regression. But it can’t explain everything.
In fact, some of the largest studies evaluating re-treatment after lasik showed dramatic improvement in re-treatment rates from the beginning of the study to the end of the study despite using the exact same technology. In the beginning of the study in 2005, the re-treatment rate was around 2.5%. But by the end of the study in 2012, the rate had decreased to less than 0.5%.
There are additional surgeon factors which influence the need for re-treatments.
Some of these may include:
- The development of nomograms to further improve accuracy after lasik
- The refinements in surgical technique to make treatments more consistent
- Improvement in lasik candidate selection or eye health/prescription optimization prior to lasik
Each of these things can influence how low the re-treatment rate after lasik will be. While some of these things surgeons have collectively learned over the years, some of these things are more individualized to the surgeon and the lasik center.
But The Eyes CAN Change Over Time
Some people may have changes in their prescription completely independent of lasik and their cornea.
For most people, the prescription of the eye stabilizes before the ages of 18-21. But for certain individuals (especially those that spend a lot of time studying such as in graduate programs), the prescription can continue to get more nearsighted with time.
This can “wear off” the lasik treatment.
Even without excessive book-work, vision CAN become slightly more nearsighted with time in our 20s and 30s. It’s not much (it may only be about -0.05 of prescription per year), but it can add up over the course of a decade or two. Because of this, some people may find that they don’t see quite as sharp in the distance 10 years out from lasik. The lasik has “worn off”.
(see also The Reasons Behind Eyesight Getting Worse in 20s).
Final note on age
As much as we want our eyes to stop changing, they never really do. (see also Exactly When Does Vision Stop Changing). And the older you get, the more your vision changes.
The biggest change that you will first notice comes during the 40s. During this decade of life, the natural lens inside your eye starts to become less flexible. As this occurs, you start to have more difficulty seeing up close. This requires reading glasses in order to be able to see up close. Unfortunately this is unavoidable; even if you have had lasik!
But this change in vision also affects how surgeons perform lasik treatments for those in their 40s and up.
Typically when surgeons perform lasik treatments, they can include a small buffer of extra prescription to help adjust for any effects of regression. This works fine for young patients who don’t have any issues with reading up close.
But for older patients, having this extra buffer of prescription means a slightly reduced ability to read (the lens must focus through that extra buffer first before focusing up close). Thus, treatment targets tend to be “tighter” in older patients with less extra buffer. This can lead to a slightly higher rate of regression (but is balanced out by optimizing the remaining ability to read up close).
And as that lens inside the eye ages even more on its way to becoming a cataract, it can actually cause changes in the prescription of the eye. This can cause your vision to shift - typically this causes you to become more nearsighted. This change in prescription from the lens can cause it to appear that the lasik has regressed. Although, cataract surgery not a re-treatment is the preferred way to correct this remaining prescription.
Lasik with today’s modern lasers is very different from lasik performed over 20 years ago. Re-treatment rates after lasik used to be very high but now it is much less common to need any lasik enhancement procedure. However, there are still things that will change over the course of your lifetime that will affect your vision and how you see from lasik.
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