The FACTS on How Long Does Lasik Last
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 most people, lasik will provide great distance vision as long as the eyes remain healthy. The retreatment rate after todays modern lasik is less than 0.5%. 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. 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 the final shape immediately after lasik may not last. The cornea does have a way it can change on its own
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.
Eye changing over time
Finally, 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 cause “apparent” lasik regression. (see also The Reasons Behind Eyesight Getting Worse in 20s).
So How Common Is Regression
Despite all those different factors playing a role in causing regression, re-treatments have gotten to be uncommon after lasik.
The chance of you having residual prescription and needing a retreatment 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 retreatment after lasik! And as you get beyond a few years out from your procedure, if you hadn’t needed any retreatment by now, you are much less likely to have any additional regression and need any enhancement.
And in fact, certain people will likely have an even lower rate.
- Younger patients are less likely to need retreatments 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 retreatment 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 retreatment 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 retreatment 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 retreatment after lasik showed dramatic improvement in retreatment 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 retreatment 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 retreatments.
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 retreatment 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.
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).
But 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 and increases the retreatment rate.
Lasik with today’s modern lasers is very different from lasik performed over 20 years ago. Retreatment 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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