After cataract surgery, a whole lot of things will change for your vision. Even after the prescription stabilizes and despite a perfect surgery the vision can feel a little off.
Now, there are a whole host of reasons why vision may be blurry after cataract surgery.
But what if only one eye is blurry? Technically you can still see, but the prescription difference between the eyes may cause the vision to be in an imbalance and difficult to deal with.
Sometimes this vision imbalance is temporary and mostly unavoidable. Sometimes this vision imbalance may be expected and in some cases even planned. But regardless of how it happens, there are many different ways to fix it such as glasses, contacts, surgery or even just time.
So read on to learn how it all happens and how to take care of it.
It's Only Temporary - Surgery One Eye At A Time
The most common way the vision becomes imbalanced after cataract surgery is simply timing.
Although both eyes can be done at the same time, the vast vast majority of cataract surgeries are still only performed one eye at a time. Until both eyes go through surgery, there will be a time when one eye is corrected with cataract surgery while the other isn’t.
Vision will be bright and clear in the recently corrected eye while the other eye with the cataract will still be dull and blurry.
But this isn’t the only problem. Perhaps a bigger issue leading to the eyes become imbalanced is the fact that you may have worn glasses prior to cataract surgery.
After cataract surgery, vision is usually corrected as much as possible for distance vision. For many people, this means that NO glasses or a much lighter glasses prescription are required to see off in the distance. If you’ve worn glasses your whole life, it will very likely be a big change from what you are used to. And while that’s great!, it does mean that in between eyes things can be really annoying.
Once the first eye is completed, the uncorrected eye may still need a large glasses prescription in order to see. This will cause a large vision imbalance between the eyes after cataract surgery.
That is, until both eyes have cataract surgery.
More Persistent Reasons For Vision Imbalance
Not everything can be solved as simply as performing cataract surgery on the second eye. For example, what if there is no planned second surgery?
Only One Cataract Needs Surgery
Some individuals may only develop a cataract in one eye. While fortunately after cataract surgery, these individuals won’t experience too much difference in clarity between the two eyes (since the other eye still sees well), these individuals can experience a difference in prescription. And as we've seen, a large difference in prescription causes a vision imbalance (a theme that we'll see repeated again and again).
Leftover Prescription After Cataract Surgery
Sometimes there can be unexpected vision imbalance after cataract surgery, even after having both eyes done. And this can happen even in an otherwise perfect surgery.
Cataract surgery has become very accurate but it isn’t 100%. Approximately 1 out of 20 people after cataract surgery can end up significantly off target.
When cataract surgery is done one eye at a time, the surgeon can adjust on the second eye if the first ends up off target. While this can help improve the ability to get out of glasses for distance, it can result in a small amount of vision imbalance between the eyes.
Fortunately, in small amounts, you may not even really notice the difference.
But even if you do end up on target, if you don't correct astigmatism during cataract surgery, this can also leave you with a significant difference in prescription.
Intentional Vision Imbalance
There is one final major group. One method of correcting vision with cataract surgery is to intentionally create a vision imbalance. One eye is corrected for distance vision, the other is corrected for up close vision. This is known as monovision.
Many people already do this with contact lenses prior to cataract surgery and this result can be replicated with cataract surgery.
How To Deal With Vision Imbalance
Small amounts of vision imbalance can be adjusted to and tolerated. If this wasn’t the case, monovision wouldn’t be possible.
In the first few months out after cataract surgery, the imbalance between the two eye steadily improves as the eyes get adjusted.
Check out Adjusting And Training Eyes After Cataract Surgery to learn more about that process.
But for the other causes, the vision imbalance may need to be treated.
Correcting imbalance with glasses
With small prescriptions, glasses can be used to match both eyes and eliminate the vision imbalance. If no prescription is required for the recently corrected eye, glasses can be simply made with a blank lens for that eye.
But glasses have limits to how much prescription difference it can treat between eyes.
When we look at an object in front of us, that object passes through the glasses and then our own eye and natural lens and is focused as a distinct image on our retina.
Light focusing in the eye; image by Sunshineconnelly at en.wikibooks, CC BY 3.0, via Wikimedia Commons
Let’s try an experiment. If you have reading glasses handy, take them and slowly push them away from your face. What you will notice is that the size of the object in front of you slowly gets a little larger. When you push reading glasses further away from you, the reading glasses actually work a little stronger. This stronger prescription creates a different size of image that you see.
The actual size of the image projected onto our retina will actually be different depending on the prescription of the glasses.
Now, this difference in size isn’t any issue when both eyes are the same. But it does become problematic when one eye differs significantly from the other.
Our brain can’t adjust very well if the images from the two eyes are significantly different sizes. This creates significant eye fatigue or even double vision.
How much is too much prescription difference? Well, many people can tolerate up to about 3.00 difference in prescription between the two eyes. (But this can vary quite a bit from person to person and even depends on how the glasses are made).
Less than that and glasses can still work to fix the vision imbalance after cataract surgery.
If you already have a pair of glasses and are waiting to have cataract surgery on your second eye, this may get you by. Learn more at What To Do About Glasses After Cataract Surgery On One Eye
When Glasses Won’t Work
If the vision imbalance between the eyes is just too high, glasses may not be a workable option. But there are other ways to correct the vision imbalance.
Contact lenses sit on the surface of the eye and correct vision. This one single difference changes the way contact lenses correct vision compared to glasses.
Glasses change the apparent size of an object because they sit further from the eye. When light passes through glasses, it is first focused through the glasses before being focused by the eye. That small gap allows for a change in the size of the image.
The contact lens sits directly on the surface of the eye. Once vision is corrected by the contact lens, it is immediately focused by the eye. There is no gap and no change in the “size" of the object. (Technically not zero change, but much less than glasses)
Therefore, contact lenses can be used with almost ANY difference in prescription between the two eyes!
If one eye sees well without correction and the other eye has more than 3.00 prescription, a contact lens can be used to correct that eye and balance the two eyes.
For those who are used to wearing contact lenses, this is the easiest solution.
When Contact Lenses Won’t Work
But as easy as a solution contact lenses provide, not all people can tolerate it. Contact lenses can cause more dry eye and irritation. Others simply don’t like the hassle of putting them in and taking them out every day.
Beyond contact lenses, laser eye surgery such as lasik can be used to eliminate vision imbalance.
Similar to how contact lenses correct from the surface of the eye, laser eye surgery does the exact same thing. It can correct large differences in prescription and put the eyes back in balance.
Lasik can especially be a great option for younger individuals (those 40-45 or less) who only had a single cataract as it preserves the focusing ability of their good lens.
But lasik is more costly than glasses and contact lenses and isn’t great for those with severe dry eye.
Cataract Surgery For Vision Imbalance
If the above options are all exhausted, cataract surgery can actually be performed in the absence of a cataract IF the initial cataract surgery caused a large and difficult to correct imbalance in vision.
Performing cataract surgery on the “good" eye can correct the prescription difference and allow the eyes to be back in balance.
If glasses or contact lenses don’t work out, this can be the best option for older individuals (those 45-50 and older). If the good natural lens has already lost flexibility due to age and is having trouble focusing up close or has some early cataract clouding, then it probably won’t be missed if it is removed to correct the vision imbalance.
Summary
Vision imbalance can happen after cataract surgery for a variety of reasons. For many, it can occur temporarily between the first and second procedure. It can also occur because of less than perfect accuracy or simply because only one eye actually needs cataract surgery. Glasses can be used to correct the vision imbalance, but glasses have limits to what they can do. When glasses don't work, contact lenses or other surgeries can be very effective at making the eyes equal again.
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