12 May What is monovision?
The AAO (American Academy of Ophthalmology) defines monovision or blended vision as a corrective measure for dealing with presbyopia or “aging eye” – the normal eye aging process that makes it difficult to focus on close objects clearly. 
As you age, you are bound to find it more challenging to read a newspaper, menu or focus on your Smartphone screen. Although it is possible to deal with such vision problems using readers or magnifying eyeglasses, it can be annoying when you must use reading glasses every time you want to read. Monovision is a viable option for individuals who wish to reduce dependence on reading glasses as they age.
Monovision means correcting one eye for really good far away vision and the other eye for good reading vision. And that way, you can see far away without glasses and you can see up close without glasses, so it’s great. You have a lot of freedom from glasses. Not everybody tolerates it. Some people don’t like the difference between the eyes, but for most people, it works very well and allows them to not have reading glasses always in their pocket or on a chain around their neck.
How does monovision work?
Monovision can be achieved using contact lenses, artificial lens implants (intraocular lenses) or through refractive surgery (such as LASIK). It works on the basis that many people have a “dominant” eye – one that sees better if you have to close one eye.
Establishing eye dominance is easy given studies have found a link between eye dominance and handedness, i.e. righties have their right eyes as the dominant eyes and vice versa although there may be exceptions to this rule. For instance, it’s harder to establish eye dominance, if you can use different hands to write. 
Monovision corrects vision in the dominant eye for distance vision while the other eye is left nearsighted to enable a person to see close objects. The eyes still work in unison allowing clearer vision at any distance. Monovision works since the brain is more focused on visual information from the dominant eye.  Distance vision isn’t significantly disturbed when a near-powered lens is fitted on the non-dominant eye to improve near vision.
Although monovision may appear complicated, most people adapt quickly to this vision correction technique. In most cases, it’s impossible to tell apart the eye that has been set for near or distance vision when both eyes are open.
What are the downsides of monovision?
In most cases, it takes a week or two for people to adapt to monovision. However, some people can’t adapt completely. As a result, it is not a universal solution to dealing with presbyopia. This is precisely why eye doctors recommend trying monovision contact lenses out before committing to a more permanent solution such as monovision LASIK surgery.
If a patient who undergoes monovision LASIK finds it difficult to adapt, the surgery can be reversed through an enhancement procedure on the eye that has been left for near vision.
Besides adaptation problems, monovision can also make a person lose depth perception (3D visual perception and distance of objects). In some cases, you may still need reading glasses when reading small print or night driving. 
Monovision can also make it difficult for you to engage in performance sports, night driving or other activities that require intricate close vision.
Preferences to the procedure can also vary based on many factors including career choices. For instance, monovision can be ideal for a 50-year old retiree but not as appropriate for a driving instructor of the same age.
Monovision: is the procedure reversible?
The good news is if we do monovision and you don’t like it, it can be reversed. We can come back and do an enhancement. We correct you for excellent distance vision in your reading eye, then both eyes see very well far away. You’re very balanced. Unfortunately, you have to then get reading glasses, but we can reverse the effect. It’s really rare that we would do that. Our tests ahead of time really help us establish whether or not you’re going to like monovision.
Is monovision the only way to fix your vision?
Monovision is the best way, and really the only way, to correct reading vision with LASIK surgery if you’re older. If you’re younger, under the age of 45, you don’t need to do monovision because you still have flexibility in your natural lenses. You’ll still have good reading vision after LASIK. But as you get older, older than 45, monovision is the way to give you good distance and reading vision, both, if that’s what you want.
Monovision: why do I need reading glasses?
It’s a really frustrating thing. You’ve had great distance vision your whole life, and now all of a sudden, you need reading glasses. Unfortunately, that happens to everyone. And the reason is the lens inside your eye gets harder with age, and loses its flexibility. It’s no longer able to focus to flex for close vision. That’s why you have to get reading glasses. There are some potential solutions for that trifocal and multifocal lens implants, monovision laser vision correction, and they can alleviate the need for reading glasses.
This article is not a substitute for a consultation with your surgeon. Before choosing to proceed with laser eye surgery your surgeon will have a detailed discussion with you about the right procedure and about the potential complications.
A unique mix of expertise, experience and international reputation, Dr Ron Binetter is the figure behind the Binetter Eye Centre. With more than two decades of hands-on experience in eye surgery, Dr Binetter is a specialist in cataract, lens implantation and laser eye surgery. Learn more about Dr Ron Binetter’s background and qualifications.