When Does The Corneal Flap Heal After Lasik?
It isn’t natural to have a flap within the cornea. That’s not how we were born. But everyday, thousands of individuals have a corneal flap created within their cornea because of lasik. The success of lasik demonstrates that the eye can survive with a corneal flap. But does this corneal flap heal after lasik?
Corneal flaps after lasik will not heal 100%. But due to the way laser created lasik flaps are created, there is a significant amount of healing to create much strength and stability. A lot of this healing occurs within the first week out after lasik and continues to progress over the following months.
Thus, it is very rare for the corneal flap after lasik to present any issue. A significant amount of healing occurs to allow the cornea to behave pretty much like a normal cornea.
About The Lasik Flap
For this discussion, we are going to be talking about laser created lasik flaps. These flaps are created using a femtosecond laser. This is the modern way of creating corneal flaps in contrast to those lasik flaps created with a blade called a microkeratome. In general, laser created lasik flaps heal much more than those created with a microkeratome. (see also Finally Make Sense of All The Different Types Of Lasik for more information)
Lasik corrects vision by changing the shape or curvature of the cornea. To do this, laser energy must be applied to the structural framework of the cornea called the stroma. To quickly get down to the stroma layer of the cornea, lasik creates a flap that is folded back. Following the treatment, this lasik flap is replaced on the surface.
An average cornea is approximately half a millimeter thick! And the lasik flap only involves about 20% of the cornea. These are very thin things. This allows the lasik corneal flap to involve as minimal of the cornea as possible.
Creation of the flap
There are two main parts to a laser created lasik flap.
- The bed of the lasik flap
- The sides of the lasik flap
This 3D geometry of the lasik flap improves the ability of the lasik flap to heal up.
What Makes Lasik Flaps Strong
So what do we want out of the healing of the lasik flap? We want strength and stability. We want it to almost be like there is no lasik flap at all. And we can get close to that goal!
When we place the lasik flap back into position onto the cornea, we want to make sure that it stays in that same location. The unique properties of the femtosecond created lasik flap helps to prevent the lasik flap from slipping or dislocating - ie, it makes it strong.
The flap sidewalls
Remember the two main parts of the lasik flap and how it leads to a 3D shape? This significantly increases the strength and stability of the lasik flap. Doesn’t seem like much, but having walls helps keep the lasik flap in place.
Imagine you are cooking pancakes on a griddle (and using lots of butter so the pancakes not only taste delicious but slide pretty readily on the griddle). This griddle has no sides; the pancake-griddle interface is a 2D plane. Theoretically, if you nudge the pancake, you can cause it to slide off the griddle and onto the floor; ruining your breakfast.
Now instead, cook a large pancake within a skillet. This skillet has walls; the pancake-skillet interface is more than just a flat surface. The walls provide extra stability to keep the pancakes within the skillet. You really have to nudge the pancake pretty hard in order to overcome the resistance of the wall of the skillet and dislodge the pancake from the skillet.
The walls of the lasik flap work in almost the exact same way! Keeping the lasik flap on the surface of the cornea.
In addition, these walls can be created with inverted bevels to make the lasik flap even stronger.
A lot of times, inflammation gets a bad rap. But inflammation can be a good thing. And this is true after lasik.
A small amount of inflammation is created at the edge of laser created lasik flaps. This inflammation eventually leads to the development of a small amount of scar tissue. This scar tissue actually will seal up the edges of the lasik flap and make them even stronger. (and has zero impact on vision)
This inflammation and development of microscopic levels of scar tissue are what allows the lasik flap to heal over time.
How Long After Lasik Until Flap Heals
Ok, now that we know what causes the lasik flap to heal up, when can we expect this all to happen?
The lasik flap is the weakest within the first 24-48 hours after lasik
There is one step that must initially occur to strengthen up the lasik flap. Until this occurs, the lasik flap is pretty weak and can be disrupted with minimal effort. Disruptions of the lasik flap most often occur during this time frame. (see also What To Do If You Accidentally Rubbed Eyes After Lasik)
On the very surface of the cornea is a skin-like layer called epithelium. When the lasik flap is created, and lifted back, a lasik-flap shape break or scratch is created in the epithelium. This break creates discomfort within the first few hours after lasik. But fortunately this break heals pretty quickly during those hours.
Until this break heals over, the lasik flap can be moved pretty easily, but after this break heals up, the epithelium forms a complete sheet over the lasik flap. It’s akin to putting a lid on our pancake skillet. The epithelium provides even further resistance to the lasik flap moving around.
That epithelium strengthens over the first week
The corneal flap heals quite a bit within the first 24-48 hours after that scratch in the epithelium heals over, but it becomes even stronger within the first week.
During the first week after lasik, the epithelium redevelops all of its tight connections. As this occurs, the epithelium becomes even stronger. This stronger epithelium protects the corneal flap even more. The strength of the lasik flap has improved considerably.
Corneal flap healing beyond the first week
But we aren’t at full strength after the first week. There is more to come. This is due to the microscopic inflammation at the edge of the lasik flap and the subtle scarring that occurs. This allows the corneal flap after lasik to get stronger with time.
Approximately two-thirds of this occurs within the first month out after lasik. And this continues to strengthen even up to three months out from lasik and beyond.
And while the corneal flap may never be as perfectly strong as a natural cornea; a significant amount of healing does occur. So much so that it’s even rare for injuries to the eye to cause an issue with the lasik flap.
Laser created lasik flaps heal up with a significant amount of strength and stability. During the first 24-48 hours, the lasik flap is the weakest. As the epithelium heals over this lasik flap, initially within the first 24 hours and then later strengthening over the first week, the strength of the lasik flap improves considerably. Gradually over the remaining months, the lasik flap continues to heal and strengthen over time.
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