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How Long Does Blurred Vision Last After Cross Linking?
It’s worse enough dealing with blurry vision from keratoconus. On top of this, it is common to have to deal with blurry vision after corneal cross linking for keratoconus as well. But, the procedure is still important in order to halt the progression of keratoconus.
Vision will be especially blurry after corneal cross linking for keratoconus during the first 7 to 10 days following the procedure. Beyond that, it is possible for the cross linking to change the prescription of the eye and make your glasses not work as well as they used to. This can continue to change years out after the procedure.
Other than those two major changes, there is another short term change worth mentioning, but it may have an almost insignificant effect on vision. So let’s explore each of these distinct phases in depth.
Initial Blurry Vision
When we look at an object, light passes through the front surface of the eye, through the natural lens inside our eye and hits the retina in the back of the eye. And especially during corneal cross linking, a lot happens on the front surface or cornea of our eye!
On the very surface of the cornea is a thin layers of cells called epithelium. These cells are responsible for providing a protective coating to all the rest of the layers below. It’s the skin of the cornea.
Normally the epithelium is very smooth. Having a smooth glass-like surface allows light to easily pass through and give us vision.
But this changes after corneal cross linking. Well, at least with FDA approved type of corneal cross linking. Corneal cross linking actually exists in different forms. The very effective form which is approved for use in the United States involves removing this epithelium layer (called “epi-off” cross linking within the medical community). As we understand and learn about corneal cross linking more, different methods, such as those that keep the epithelium intact, may become the dominant way we treat those with keratoconus in the future.
After we remove the epithelium, it must regrow. This regrowing process takes approximately 3-5 days. But here’s the thing, without the epithelium, the surface of the cornea is no longer glass-like. The layers below the epithelium are much more rough. Like a stained glass window, it is much more difficult to look through the cornea. Light scatters instead of passing through cleanly. Your vision is blurry!
This blurry vision will last at least 3-5 days, the same time that it takes for the epithelium to regrow, but can last just a little bit longer, up to 7-10 days waiting for that epithelium to become perfectly smooth again.
During this healing process, your surgeon will add a contact lens to the surface of the eye. This contact lens doesn’t correct prescription, it simply serves as an “artificial epithelium” to help protect the eye and make it feel more comfortable during the recovery (since it is painful not having an epithelium).
But because tears underneath this contact lens can mask the rough surface of the cornea, it can improve vision slightly more, at least in the beginning. As the epithelium grows, it can add some extra distortions. Thus, you can find in the first 3-5 days that your vision gets worse before it gets better.
Haze After Cross Linking
Once you get past the initial immediate causes of blurry vision after corneal cross linking, you still aren’t fully in the clear. Haze can create one possibly insignificant or minor effect on vision.
It stands to reason that anything creating cloudiness of the cornea can cause some blurry vision. After-all anything that creates cloudiness is a barrier for light passing through. After corneal cross linking, haze develops within the cornea for the first few months.
The cornea isn’t meant to be blasted with UV light. When combined with riboflavin, it’s great to strengthen the cornea. But the cornea still must heal up from this irradiation.
Haze is the healing response of the cornea after corneal cross linking. The tight and organized framework which allows the cornea to be transparent becomes slightly more distorted. Extra light is scattered causing some haze.
Most people will be none the wiser that haze has developed on the cornea. Haze really is something more academic than relevant. But haze can potentially cause some extra glare or fog-like symptoms after corneal cross linking. These can build up to the second month before gradually resolving over the following months.
The Biggest Change On Vision
So far, most of the blurry vision after corneal cross linking has been within the first week. With a few minimal changes beyond that. But over the long-term, there is a bigger effect on vision: the prescription of the eye.
As keratoconus gets worse, the prescription of the eye changes. Keratoconus causes the cornea to become weaker. As the cornea becomes weaker, it is less able to maintain a dome shape. This causes the cornea to bulge out and form a cone shape. The cornea becomes steeper as a result.
Steeper cornea with keratoconus; image by Madhero88, CC BY-SA 3.0, via Wikimedia Commons
This steeper cornea changes how light focuses in the eye. Ie, it changes your prescription; the prescription of the eye becomes more nearsighted (also with a high amount of astigmatism).
So what happens if we make the cornea stronger? Well, this partially reverses everything!
A stronger cornea is able to maintain that dome shape better. The cornea bulges less. The cornea becomes less of a cone shape; it becomes flatter.
This flatter cornea REDUCES the amount of nearsightedness and astigmatism! This can improve overall vision.
While this typically is great, there are a few problems:
Glasses don’t work as well
Glasses can’t adjust to all the changes with your cornea and prescription on their own. This means that while you may have gone into the surgery with a perfectly optimized prescription to give you your best vision possible, you may have come out of the surgery with a glasses prescription which is “off”.
Our natural lens inside our eye does have the ability to adjust to some of these changes. In particular, our natural lens is able to focus through extra nearsighted prescription to sharpen things up.
Because the changes after corneal cross linking can leave you with a pair of glasses with extra nearsighted prescription, you may not even notice the change in prescription. And some people don’t really have a significant change in the shape of their cornea and thus prescription after cross linking.
But if the cross linking causes changes in astigmatism, it can potentially really throw off your prescription causing you additional blurry vision.
The changes happen over time
If the cornea completed all of its changes after corneal cross linking in two to four weeks, while it would still be annoying to have to get a different prescription, you could take care of it once and for all.
But the cornea keeps on changing! In fact, the cornea can change for YEARS! This could mean more frequent adjustments to glasses and contact lenses in order to optimize your vision.
While it still can change over years, the vast majority of change happens within the first year after corneal cross linking. After that mark, changes to the prescription of the eye slow down.
And again, not everyone will notice these changes to prescription.
The first phase of blurry vision after corneal cross linking occurs during the first week following the procedure. This blurry vision heals up within 7 to 10 days as the eye recovers. Following this phase, corneal cross linking can change the prescription of the eye and make your glasses work less effectively - blurring vision. This can continue to change for years out from the procedure.
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