March 21, 2023 | Lasik

The Reason For Fluctuating Vision After Lasik

By Barrett Eubanks, M.D.

The Reason For Fluctuating Vision After Lasik

Lasik corrects vision by changing the shape of the cornea. That must mean that the cornea is key for focusing light into the eye. Wrong! Well, partly right.

The shape of the cornea is important for the prescription of the eye. But there is another “structure" which technically does the real focusing.

What I’m talking about is a layer of tears that rests on top of the cornea. This is called the tear film.

This tear film can become weaker after lasik and dry out quicker. When the tear film dries out, vision can become blurry and fluctuate. The tear film is thus to blame for fluctuating vision after lasik.

But there are ways to improve and fix. So let’s first examine what is going on and then what you can do about it.

Introduction To The Tear Film

Everything that you see must first pass through the tear film before reaching the cornea and the rest of the front of your eye. It is technically the tear film which focuses most of the light within the eye. But because the tear film conforms to the shape of the cornea, changing the shape of the cornea with lasik is able to correct vision.

But while the tear film is important to give us good vision, the key functions are actually to provide nutrients to the cornea and prevent the eye from drying out. Having a good healthy tear film keeps the eye healthy and comfortable and also provides for stable vision.

Enter Lasik & Dry Eye

In our eye is a tear gland that produces tears. Nerve connections from our eye tell this gland to produce more tears whenever the eye becomes more dry.

Lasik disrupts these nerve connections. Creating a lasik flap and reshaping the cornea breaks these nerve connections. Eventually these nerve connection regrow, but until then the eye has more difficulty producing tears.

This means less tear film.

Most people will notice this because the eye dries out a little more. When the eye dries out, they will experience the feeling like there is something in the eye or a burning or gritty sensation.

But because the tear film is so important to vision, some people will also notice fluctuating vision after lasik.

Fluctuating Tear Film = Fluctuating Vision

On a calm day, sitting next to a smooth flat pond, you can see right through (assuming the water is clean).

Fish in plain view in clear pond
This fish can’t hide in this smooth flat pond; image by Ricky Davis on Unsplash

Same thing with the tear film. When the tear film is smooth and flat, vision passes right though and we see.

But if the tear film dries up, it becomes irregular. Light scatters when passing through and vision becomes blurry.

So we blink. And our eyelids work like squeegees to smooth out the tear film. Our vision sharpens up again.

If you were to hold your eyes open without blinking long enough, your tear film will dry up. But because we regularly blink our eyes (about six times a minute), a normal healthy tear film is able to stay flat and smooth until we blink again - preventing the tear film from drying out and blurring our vision.

But if the tear film is inadequate, it will dry out before we blink again. What this leads to is fluctuating vision. Immediately after blinking, the vision sharpens up (in fact, you may even be able to read the 20/20 letters); but when the tear film dries up a few seconds later, vision becomes blurry.

Because lasik can reduce the volume of the tear film in the short term, this can make the tear film more likely to dry out and fluctuate after lasik.

What Else Makes The Tear Film Worse

Lasik isn’t the only cause of having a weak tear film. In fact, there are many other reasons the tear film can dry out quicker - pretty much any other cause of dry eye. And most people who do have fluctuating vision after lasik more than likely have other causes of dry eye that add to the lasik.

Contrary to popular belief, our tears aren’t just all liquid. In fact, sitting on the surface of the tears is an oil or lipid layer. (And sitting between the cornea and the liquid layer is a separate mucous layer which sticks the tears to the surface of our eye).

Layers of the tear film on our cornea
Layers of the tear film on our cornea; image by NIH Image Gallery from Bethesda, Maryland, USA, Public domain, via Wikimedia Commons / modified from original

This oil layer is a major cause for tears drying out too quickly.

Within our eyelids are tiny glands called meibomian glands. This oil layer gets produced in these glands. But, if the quality of the oil produced isn’t good, this oil layer isn’t very effective and tears simply evaporate away. This can be further complicated by an overgrowth of our normal skin bacteria on our eyelids, called blepharitis, which can destabilize the tear film even more.

So between tears evaporating too quickly as well as not producing enough tears, a perfect storm exists to cause fluctuating vision after lasik.

And of course, any other medications or medical conditions that dry the eye out only add to the issue.

Check out Learn Exactly Who Should Not Have Laser Eye Surgery for more on conditions and medications that dry the eyes out.

Worse When Reading

Aside from other causes of dry eye, fluctuation of vision will also be made worse when we do certain activities, such as reading.

Remember how blinking restores a smooth tear film again? And how we blink about six times a minute? Well this blink rate can drop depending on what we are doing.

When performing tasks that involve a high degree of concentration or focus, we blink much less. Up to 5 times less frequent! This includes working on the computer, reading, and can include driving. Blinking less means more time for the tear film to dry out and blur our vision.

What To Do About It?

It can be incredibly annoying getting lasik done to sharpen up your vision only to suffer with fluctuating vision afterwards. But there are ways to improve it and heal things faster.

The most simple way involves artificial tears. While important for everyone after lasik, they become even more important when the tear film is weak.

Artificial tears thicken up the tear film to keep it from quickly drying out.

In fact, you may have noticed that artificial tears can temporarily fix the fluctuating vision. Putting the artificial tear drop in can provide clear vision - at least for a few minutes.

To help provide longer relief and improvement, try switching to a thicker gel-based artificial tear or a more advanced one. Visit These Are The Best Eye Drops After Lasik to learn all about the different types.

Also Treat Causes of Dry Eye

Artificial tears are more of a temporary short term solution (but are still helpful to prevent the dry eye from becoming worse).

But to really improve things more, it is important to treat any other causes of dry eye. Ask your doctor for treatments that are the most important for you.

  • If your eyelid meibomian glands aren’t producing good oils, starting an omega-3 supplement can help. Using a warm eyelid mask can also heat up the oils and allow them to flow easier onto the eye.
  • Blepharitis can be effectively treated by cleaning the eyelids with eyelid cleansing wipes (but be sure to wait at least a week to avoid rubbing the lasik flap out of position by inadvertently rubbing the eyes)
  • Great prescription eye drops exist (and even a dry eye nasal spray) which can reduce inflammation on the eye and / or stimulate tear production.
  • And one other way to thicken the tear film is to prevent it from draining away as quickly from the eye by reversibly or temporarily plugging small eyelid drains called punctum.

Getting on top of the dry eye and aggressively treating it is the best way to improve and resolve the fluctuating vision.


After lasik, the tear film which rests on the surface of our eye can dry out quicker than normal. This can cause the vision to fluctuate. Using artificial tears is the best way to stabilize and resolve the fluctuation of vision but it is also important to treat other causes of dry eye as well.

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