Going into PRK, expect to have blurry vision for quite a while. It simply takes time for the vision to sharpen up all the way to 20/20. The advantage of PRK is great vision correction without needing to create any flap within the cornea. An advantage is NOT quick recovery.
And so your vision will heal up in different stages. The first week things will be the most blurry. As you get to the one month mark, things will heal up a lot more but it is still normal to have some degree of blurred vision. Fortunately by the 3 month mark, vision recovery has pretty much completed for most people.
Here is what you can expect at each stage after PRK.
Within the first week
A lot will happen within the first week after PRK. This is really the worst stage of recovery after PRK.
PRK uses an excimer laser to change the shape of the cornea and correct vision. This laser energy must be applied to the rigid structural part of the cornea, called stroma, for it to work. But turns out there is another layer in the way called epithelium. This layer serves as the skin-like layer of our cornea.
Epithelium and stroma of the cornea; Image by StemBook (CC BY 3.0) / modified from original
Lasik creates a lasik flap to get past the epithelium. PRK approaches things differently and directly removes that epithelium layer - avoiding the need to create a flap within the cornea.
This epithelium must then heal back. This gives us our recovery for the first week.
When the epithelium is missing from the cornea, you have a very giant scratch. Having a small scratch will cause some pain and blurred vision, having a giant scratch will cause a lot more. Thankfully a contact lens is usually placed to help with the pain.
Vision works best when looking through a clear surface. Having an intact epithelium creates a clear surface. But when this epithelium is removed, the surface becomes rough. Your vision becomes blurry. How blurry? Well, only about 40% of people are able to reach the legal driving vision of 20/40 within the first few days after PRK. In fact, the vision can get slightly worse in the first few days as the irregular margins of the healing epithelium start to grow into the center of vision.
Fortunately this heals up. Within about 3-4 days, the epithelium has healed over the giant scratch. As the epithelium continues to become smooth again, the vision continues to sharpen up over the course of the rest of the week. How sharp? Well, don’t expect to be perfectly 20/20 just quite yet. Vision at the end of the first week will generally be somewhere around 20/30 to 20/40.
More functional vision, but there is still more vision recovery to come.
1 Month After PRK
So we’re there right? Well…no
Vision improves between the first week and the first month out after PRK. But it is still normal to have blurry vision one month out.
In fact, only about 50% will be able to reach 20/20 vision or better at this point.
So what’s going on?
It takes some time for the prescription to stabilize after a PRK treatment. And at the one month, the prescription isn’t yet stable. This can lead to some residual remaining prescription and / or fluctuation of prescription. This remaining prescription will make vision a little more blurry. Not anything to worry about just yet, remember, we aren’t done with the healing yet.
But even if you can see 20/20, vision just may not seem very clear. This is due to something called higher order aberrations.
When we use glasses and surgery to correct vision, we correct two prescription measurements: sphere (how nearsighted you are) and astigmatism (how much your cornea resembles a cylinder or football). These two different measurements are called lower-order aberrations and can easily be corrected with glasses and surgery because they are symmetric and regular.
But there's more that blurs vision. Higher order aberrations have a more irregular and uneven shape and can't easily be corrected with lenses. It include things such as spherical aberration, coma, and trefoil. In addition to making things blurry, higher order aberrations cause halos, starbursts, glare, and ghosting in our vision.
Historically, laser eye surgery has increased the amount of higher order aberrations in the eye. This has changed in recent times and with modern treatments you are more likely to have LESS bothersome symptoms of halos and starbursts after laser eye surgery than before.
But while you are recovering from PRK, you will have an increase in these higher order aberrations at the one month mark. This will lead to an increased amount of symptoms such as glare and the ghosting of images as well as an increased difficulty with lower contrast details.
3 Months After PRK
We are finally making some progress.
In fact, by about 3 months, the blurry vision after PRK may almost be entirely gone!
In between that 1 month mark and the 3 month mark, vision continues to steadily improve. The prescription of the eye stabilizes and with this comes improvements in what you can see. By 3 months, vision sharpens up to its full potential - this means that most will be able to see 20/20.
That extra glare and ghosting at the 1 month? That’s gotten better as well.
If we look at someone treated with PRK and someone treated with lasik, objectively their vision is finally equal 3 months out.
But there is more than just objective numbers..and subjectively, vision may be very close but may not fully seem 100%. But fortunately even that resolves by 6 months after PRK.
Blurry Vision Beyond 3 Months Out
The typical timeline applies to most patients after PRK. But of course, not every patient will fit neatly into this recovery. There are a few things which can cause blurry vision outside of the usual normal recovery of PRK. Here are some of the most common things: (but this doesn’t include everything and its important to visit your doctor if things continue to be blurry)
Residual Prescription Error
Vision sharpens up within 3 months after PRK all assuming that everything is 100% accurate. But unfortunately this won’t always be the case. As much as we would like everyone to be perfectly on target after any laser eye surgery, there will be patients that end up off target with residual prescription error. Having some residual prescription means blurry vision (without glasses).
Luckily this doesn’t happen very often. Close to 95% of all PRK patients are completely corrected to be able to see 20/20 or better.
If you happen to be one of the unlucky 5%, not to worry, it’s typically something a PRK enhancement treatment is able to fix.
Dry Eye
Anyone who has laser eye surgery will have an increase in the amount of dry eye within the first few months after the procedure; PRK patients aren’t spared from this.
Removing the epithelium and making it grow back creates a lot of inflammation on the surface of the eye. The inflammation is trying to respond to the “injury" the surgeon created. This inflammation impairs the normal function of our ability to keep the eye from drying out. As a result, the eye dries out easier until this all heals up.
Vision can become blurry or fluctuate when the eye dries out. On the surface of the eye is a tear film. When healthy, this tear film is smooth and crystal clear. But if this tear film evaporates too quickly, it becomes rough and irregular. This blurs vision temporarily until blinking restores a smooth tear film. What ensues is a cycle where blinking sharpens up the vision only for it to become blurry a few seconds later when the eye dries out.
After PRK it is important to use frequent preservative free artificial tears to treat this dry eye and allow the eye to heal up. Check out These Are The Best Eye Drops After Lasik (also applies to PRK) to learn which artificial tear drops work best.
While much of this heals up within the first 3 months, some can notice dry eye beyond (especially those who noticed some dry eye beforehand).
Haze
One feared issue with PRK is the development of haze. Developing haze long after PRK can cause the prescription to regress, cause extra glare and cause the vision to be blurry.
Fortunately problematic haze has become very uncommon with modern PRK treatments. In fact, unless you are highly nearsighted, your risk is less than 0.1% (and even if you are highly nearsighted, that risk only goes up to 1%).
Learn more at What YOU Can Expect With Post PRK Haze
Summary
Vision takes a long time to sharpen up after PRK. The first week out after PRK will have the most blurred vision. Once that surface heals over, vision steadily improves. By month 1, vision has sharpened up significantly but it isn’t until month 3 that vision no longer becomes blurry.
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