Monovision is one of the oldest techniques to get out of glasses. For years and years, monovision has been used with contact lenses. When laser eye surgery came out, monovison was also successfully utilized to reduce the need for glasses. And just like with contact lenses and laser eye surgery, monovision can also be used with cataract surgery.
Monovision with cataract surgery works very well. Many people are able to adjust to monvision and significantly improve vision without glasses. However, monovision isn’t perfect. For many, there will still be times reading glasses will be required; especially to see smaller details. Monovision can also make nighttime vision a little more challenging.
The good news, is that advances in cataract lens technology have improved how monovision works.
But before we get into those details, let’s refresh our knowledge on how monovision works.
How Does Monovision Work
After cataract surgery the prescription of our eye changes. This is due to the new artificial lenses that replace the cataract.
Before cataract surgery, you may have some prescription error that requires glasses. But when selecting the prescription of the new artificial lens, your cataract surgeon can eliminate most if not all of that prescription error and give you much better vision without glasses; typically for your distance vision looking far away.
This new cataract lens CAN’T change focus. Because of this, up close vision is typically blurry after cataract surgery and requires reading glasses.
But not everyone wants to wear reading glasses after cataract surgery, and so there are alternative ways to improve up close vision. One of those is monovision.
We have two eyes. What if we intentionally focus ONE of those eyes for up close near vision? Well, then you have monovision.
Sounds unusual, but surprisingly it works very well. Our brain can tolerate small differences in prescription between our two eyes. After a short adjustment period, many people are successful adapting to monovision.
Learn more how monovision works at Is My Brain Adjusting To Monovision?
The Advantages Of Monovision
There are really two main pros of monovision. After-all, there is really only one main goal with monovision: get out of glasses. Does monovision meet that goal?
- The first pro is that monovision does that pretty well. If it didn’t work to get people out of glasses, nobody would do it. With monovision, you are able to see the computer and read much better than if both eyes were focused in the distance.
- The second pro is that many people are able to successfully adjust to monovision. With surgery, the success rate is generally between 90-95%.
The Downsides of Monovision
But monovision isn’t perfect. There are some cons of monovision. It’s not an absolute perfect solution.
- The biggest con of monovision is that for many it won’t completely get you out of glasses.
There are limits to how much prescription difference our brain can tolerate. Having a smaller amount of prescription difference allows for much greater success adapting to monovision. (This smaller difference in prescription is often coined mini-monovision or blended vision to distinguish it from traditional monovision).
The more reading prescription you add, the better the ability to read; but also the bigger the prescription difference between the two eyes.
Having a smaller but easily tolerated prescription difference between the two eyes won’t provide perfect reading vision. And about 70-75% of everyone with mini-monovision WILL require reading glasses for some amount of reading (typically small print or in challenging darker environments).
Making the reading prescription stronger can improve the ability to read without glasses, but it can reduce your odds of adjusting to the monovison. And eventually, if you make the reading vision too strong, it becomes difficult to see things a little further out such as the computer.
- Monovision can add some additional glare and can make nighttime driving vision more challenging.
Normally the brain is able to ignore the up close eye. This is why monovision works. But at nighttime, it becomes more difficult to ignore that up close eye. And since that eye isn’t sharp for distance, it adds a blurry image to what see. This can result in extra glare. For some patients, it’s bothersome enough to use a temporary pair of nighttime driving glasses to correct both eyes for distance and allow for comfortable driving.
Comparison Between Multifocal Lenses
Monovision isn’t the only way to get out of glasses with cataract surgery. The other way this is done is through special lenses which allow for each eye to simultaneously focus far away in the distance and up close. Read more about those lenses at Your Complete Guide Of Lenses For Cataract Surgery.
Multifocal (and more recently trifocal lenses) will provide more reading vision and more freedom from reading glasses than monovision. But it doesn’t do so without some of its own tradeoffs. These lenses do come with more glare, halos and starbursts than monovision. In addition, some may notice a slight faded or waxy vision due to a subtle reduction in contrast from these lenses; a reduction in contrast that also limits the successful use of these lenses when there are other eye problems. And while our brains are again capable of adjusting to these new lenses, monovision provides a good alternative to reduce the need for glasses.
Improving Monovision
Despite monovision being such an old technique, modern advancements in cataract surgery have improved how we use this technique. In particular, advancements in lens technology have reduced the need for glasses with monovision.
Multifocal lenses correct vision by splitting light. This is why multifocal lenses come with the additional symptoms of glare, halos and starbursts. But a new lens technology works instead by bending or reshaping light to extend the range of focus. This type of lens is aptly named an “Extended Depth of Focus Lens".
To be fair, these new extended depth of focus lenses still don’t provide as much up close vision on its own as a multifocal lens. The bending of light is only able to cover far away vision and intermediate or computer vision. But this new lens does open up more opportunities for monovision.
Because these lenses provide a larger focus range than a standard cataract lens, better reading vision can be obtained through monovision - even at less prescription differences!
This not only means better ability to adjust to the monovision (because of less difference in prescription), it also means less need for reading glasses. And performing monovision with cataract surgery in this way with extended depth of focus lenses can decrease the need for reading glasses from 75% to about 35% or less.
And of course, this reading vision can even be improved further with just a little bit more difference in prescription.
Summary
Monovision provides a great way to reduce the need for glasses after cataract surgery. But for most, monovision won’t be able to eliminate glasses completely; reading glasses may still be required from time to time. But new extended depth of focus cataract lenses have improved how we can correct vision with monovision.
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