One crazy step of lasik involves placing a tiny ring on the eye. But even crazier still, this ring actually suctions onto your eye! Fortunately this isn’t painful (because of numbing eye drops), but it does create a bizarre experience. The success of lasik actually depends on this suction ring.
The suction ring is essential in Lasik to ensure the lasik flap is created appropriately. By suctioning on the eye, it is able to stabilize the eye and prevent any eye movements. This allows the laser to create perfect reproducible lasik flaps.
Occasionally the suction ring will be unable to obtain suction or actually break suction during a lasik treatment. While this can be stressful, this may just add extra inconvenience to your vision correction.
How Lasik Flaps Are Created
The cornea isn't very thick. In fact, the whole thickness of the cornea is only about half a centimeter!
Now imagine trying to use your hand to precisely create a lasik flap into the cornea. Maybe you can create some form of a flap but the outcome probably won't be very good.
Fortunately we don't have to worry about that because machines are used to create the lasik flaps. And trust me, in this case, machines are much better than what humans can do.
The Old
When lasik first arrived, the machine was a small bladed instrument called a microkeratome. A microkeratome consists of a blade which is used to create a smooth flat cut within the cornea. (don't worry, the eye is numb for all of this)
But what happens if the eye moves around during all of this? This can change where the blade is cutting and lead to issues creating the lasik flap.
Thus, a suction ring is used to hold the blade in the same position during the entirety of the cut.
The New
The suction ring didn't go away when lasik transitioned to all-laser treatments.
Instead of a blade, a laser is used to create the lasik flap. The particular type of laser used is called a femtosecond laser. Instead of cutting like a blade, the laser precisely places small laser spots; way too small to be seen with the eye or even under a microscope. Each of these spots forms a microscopic air pocket in the cornea. One millionth of a billionth of a second later, ie one femtosecond (hence the name), the laser places a second spot directly adjacent. This pattern continues until there is a flat plane of these spots. The laser then does the same process vertically to create the edges to the lasik flap.
It is only after all of these tiny pockets are created that the surgeon manually completes the connection to have a full and complete 3D lasik flap.
But despite how fast the laser is able to work, it still takes about 20-30 seconds for the laser to create all of these billions of pockets. If the eye is able to move around this, there is no way that each of the spots would be placed in the exact spot needed to create a complete lasik flap.
Thus a suction ring is still used with modern all-laser lasik. The suction ring stabilizes the eye (and also prevents you from blinking through the treatment) and ensures that all the laser spots are created exactly where they need to be.
What Can Go Wrong With The Suction Ring
Ok. Seems straightforward. But the suction isn’t always foolproof.
Everyone's eye is shaped slightly differently with different curvatures to their corneas. Some people have steeper corneas. Some people have flatter corneas. Same goes with the width of the cornea as well. Some people have more narrow corneas than others. Overall, there is just a wide variety of eyes.
And this suction ring must be designed to fit all these different eyes. That’s a tall task.
Some laser manufacturers have gone the one size fits “all" approach. Other laser manufacturers have instead opted to offer a few different sizes in order to help ensure that proper suction is obtained.
And while this does work for almost everyone, it isn’t 100%. Rarely, no matter how hard we try, the suction ring just won't be able to achieve full suction on some patients. In this case, lasik just won’t work and an alternative laser correction procedure such as PRK is typically pursued instead.
And for other patients, you can initially get suction and treatment is started, but the suction just isn’t very strong. During the middle of the treatment, the suction can break. This leaves an incomplete or irregular lasik flap.
When this happened with the blade, lasik must be aborted. The eye is left to heal up and then PRK can be performed at a later date.
With the laser, there are fortunately a few more options.
- If the lasik flap has become irregular (because of significant eye movement before the surgeon was able to stop the treatment), than lasik is aborted, the eye is left to heal up and then PRK can be performed at a later date.
- If the lasik flap still looks regular but is just incomplete, the laser treatment can often be re-attempted. This is especially true if the flat lasik bed was already fully created - the laser is simply programmed just to create the new vertical edges. This all assumes that adequate suction can be achieved.
Fortunately having the suction break during lasik may just add extra inconvenience to getting your vision corrected rather than anything worse.
What You Experience With Suction Ring
There are two major changes that you will notice when that suction ring is applied to your eye:
The first is that you will notice a large amount of pressure. The suction effect will increase the pressure of the eye. The pressure from the laser will also increase the pressure of the eye. And you WILL FEEL this pressure! It can startle you if you are unprepared.
This pressure sensation will also cause your vision to fade away. In the back of your eye sits the retina. The retina takes visual information and sends it through the optic nerve to the brain. When the pressure increases in the eye, this blocks the eye’s ability to send this visual information. This causes your vision to fade away to black. Frequently this isn’t immediate, it will take a few seconds for everything to fade away.
Summary
The suction ring is used during lasik to stabilize the eye. This allows the laser to precisely place its treatment and create the lasik flap. While this works for almost everyone, there are some people where this suction ring may not work or even lose suction during treatment. Fortunately these can be managed well.
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