Monovision has been around almost as long as people started needing reading glasses. Well, not quite that long. But at least as long as people have been wearing contact lenses. Why has monovision existed for so long? Because it can be a really great way to get out of glasses.
Generally, our brains are set up well to adjust to monovision. Because of this, many people are successful in adjusting to monovision with contact lenses or through corrective surgeries such as lasik or cataract surgery. But not all. Most people love it. But no matter what, there will be some people who don’t. And it’s unlikely those who hate monovision will adjust over time.
There is a lot to unwrap about monovision. So lets explore:
- What actually happens with monovision and the tradeoffs
- How our brain adjusts to monovision
- Can we do anything to improve our monovision success
What Is Going On With Monovision
We have two eyes. Each eye works together to enhance what we see. But our eyes don’t actually process vision. Our eyes are just like photocells in a digital camera. The picture in front of us actually gets transmitted from these photocells to our image processing CPU - ie, our brain.
So with two eyes, the brain takes that visual information and sums it up to provide a picture better than each individual part. If you close one eye, you may notice that vision out of one eye doesn’t look as good as vision out of two eyes.
But yet monovision intentionally prevents the two eyes from working together by changing the focus of an eye!
However monovision is popular because it is done for a good reason: presbyopia.
What happens in presbyopia
When we are young, the natural lens inside our eye is capable of changing shape. If we are looking at a sunset off in the distance but suddenly want to look down and read our phone, the lens changes shape to focus on the phone instead. It does all this seamlessly.
And this is all great until this stops working. Gradually, the natural lens becomes less flexible over time and we lose the ability to see up close. To read our phone instead, we need to throw on a pair of reading glasses or progressive glasses. (or if you are nearsighted already, you can just take off your glasses)
But not everyone like glasses.
Monovision can “fix" presbyopia
So, instead of having two eyes focused for the distance and zero eyes focused for up close. Many people choose to do monovision and have one eye focused for the distance and one eye focused for up close.
This gives back the ability to read without glasses.
Not a perfect solution
Monovision provides a compromise between vision and freedom from glasses. Monovision won’t restore the vision you had back in your 20s when the natural lens was working perfectly. Instead we give up a few different things in order to be able to be able to read without glasses.
- We don’t see as sharp as what we would see using both eyes together. You will only see as sharp as one eye can see.
- We don’t have the same depth perception. Perfect depth perception comes from each eye providing a slightly different picture to the brain. The brain is then able to create a 3D space around us. When the brain is only provided visual cues from one eye, it can’t create as robust of perception of depth.
- Having monovision will cause some additional halos and glare due to the blurring of one eye.
But despite all of the apparent downsides, monovision enjoys a high success rate. Our brain is able to overcome many of those drawbacks.
People Adjust To Monovision
The success rate of monovision with contact lenses is around 75%.
The success rate of monovision with surgery such as lasik and cataract surgery is even higher at around 90-95%.
And it’s not even just people begrudgingly “putting up with" monovision. Despite the fact that monovision causes real physical changes in vision, individuals who adjust to monovision aren’t affected by those changes and enjoy the flexibility that monovision offers.
How the adjustment happens
It all comes down to the ability of the brain to ignore or suppress the visual information from an eye.
When one eye becomes slightly blurry, our brain turns OFF the input from that eye. This happens immediately due to complex signaling pathways in our brain.
And this happens to everyone! Whether you can adjust to monovision or not. The part of the eye responsible for fine detail is effectively shut off and all the input comes from the other non-blurred eye. Until you cover and compare eyes, you may not even know one eye has become slightly blurry.
However, not everyone has the same ability of blur suppression. Some people can suppress a larger difference in blur between eyes than others (such as the blur created with monovision).
Those that can suppress blur better generally do better with monovision.
Thus, there are some physiological limits to how well you’ll adjust to monovision. Some people just do better than other.
Will it get better with time?
Our brain is capable of adjusting to a lot. But with monovision, if you don’t initially adjust to it, chances are low that you will eventually get there.
Many people with monovision know whether it works for them within the first few weeks. As mentioned above, there are just some differences between individuals that can’t be overcome.
Beyond this period, for those that do tolerate monovision, there can be small improvements in the ability to use the eyes over time. While the visual information doesn’t change, our ability to use this visual information in our day to day for reading or performing tasks gets better.
Not adjusting? Well, not all hope is lost. There could be things preventing you from adjusting to monovision.
Roadblocks Preventing Adjustment To Monovision
While there are some things that we can’t change about our eyes (such as our ability to suppress blur) and our ability to adjust to monovision, there can be some things you can change to increase your success adjusting.
Suppressing blur isn’t the only formula to adjust to monovision. We can’t forget that “what we see" is also important.
Reduced vision
You can be successful with monovision even with one eye being out of focus as long as overall you can see well. Stated another way, anything that blurs your vision and makes it harder to see will make monovision harder for you.
When both eyes work together, the brain can compensate and adjust a little for things blurring your vision. But in monovision, little things that may blur your vision become more significant.
What can blur your vision?
- Having uncorrected astigmatism
- Having significant dry eye
- Having other eye pathology such as cataracts
Having the sharpest vision in each eye provides the best opportunity for success with monovision.
Changing monovision prescription
Perhaps the monovision prescription you have is too much. Perhaps you can only tolerate so much difference. Then reducing the prescription difference between the eyes may make you more likely to achieve success with monovision.
With contact lenses this can easily be done with a change in your prescription. But this can also be done with surgical monovision through an enhancement procedure.
Reducing the amount of monovision does come at a cost, however. You won’t be able to read as much and will require reading glasses more frequently. But if this is the only way monovision will work for you than it becomes a necessary trade-off.
Summary
Despite the apparent drawbacks, many people have done very well and continue to do well with monovision. And a lot of it has to do with built-in mechanisms of our brain to control what we see. But everyone’s eyes and brain work differently and so monovision won’t work for everyone. But there are some things that can be worked on to give the best success of adjusting to monovision.
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