Monovision

People who have lost their accommodation, but still have good distance vision, may only require glasses for reading.  In contrast, people with presbyopia in combination with other types of refractive errors may require other or additional types of glasses. Common refractive errors are: myopia (difficulty seeing far distances), hyperopia (more blur at near than at distance) and astigmatism (blur or distorted vision at all distances).

People with myopia who have lost their accommodation may be able to see close-up objects by simply removing their distance glasses. However, people that want to leave their eyeglasses on all the time (even people with myopia) will need multifocal eyeglasses, which allow for focusing at various distances. Bifocal eyeglasses have two prescriptions (distance and near). Trifocal eyeglasses have three prescriptions (distance, intermediate, and near). Progressive (no line multifocal) eyeglasses have a progressive change of focus from distance to near. 

There are other options besides wearing eyeglasses for patients dealing with presbyopia. Many people wear contact lenses. As with eyeglasses, patients can wear contact lenses (for distance correction) or multifocal contact lenses. However, some contact lens wearers do not like the disadvantages of having to wear reading glasses or multifocal contact lenses- Multifocal contact lenses can potentially create blur and glare at all distances. They also tend to be more expensive than single focus contact lenses. As a compromise, some people choose the monovision or blended vision approach with single-focus contact lenses. 

The contact lens used to provide good distance vision is typically put on your dominant eye and the contact lens used to provide good near vision is typically put on the non-dominant eye. 

The beauty of contact lenses is that patients can try monovision out first before committing to this. If the patient is not seeing clearly or is uncomfortable, the eye doctor can try putting the distance corrected contact lens on the non-dominant eye and the near corrected lens on the dominant eye to determine if this is clearer and more comfortable for the patient. 

There is also a technique which combines monovision and multifocal lenses called “modified monovision”. An eye care professional can fit you with a multifocal contact lens in both eyes. If near vision is still not clear even with the maximum near power available (near powers often come in low medium and high near powers, called “add”), one eye can be made clearer for near vision. The eye that is made clearer for near (usually the non-dominant eye) will be more blurred for distance vision.

• The main advantage of monovision is that a broad range of vision can be achieved by correcting one eye for near vision and another distance. Monovision with contact lenses can be used as a trial run for permanent monovision procedures, so you can test if this approach is right for you. 
• There is also a cost factor associated with the price of lenses. Multifocal lenses (both contact lenses and IOLs) tend to be more expensive. Monovision with single-focus lenses allow patients to potentially be free of eyeglasses without the added costs involved with multifocal lenses.
• Monovision with single focus lenses can also be a suitable alternative for patients who want the broader range of vision without risking side effects associated with multifocal lenses (like nighttime glare and halos). 

• The main disadvantage of monovision is that one eye sees clearly at a distance, while the other eye will be blurred at a distance (since it’s targeted for near vision). Another disadvantage of monovision lenses is that only distance and near vision is corrected. Intermediate range (such as the computer monitor, which is often at arm’s length away) may be blurred. Unfortunately, we do not have a third eye to take care of this intermediate range.
• It is possible to have the near vision corrected eye altered to see more clearly at intermediate ranges, but then very close objects will be more blurred.