WHAT IS MONOVISON AND HOW DOES IT CORRECT PRESBYOPIA

Medically Reviewed by Dr. Sony Sherpa (MBBS), 1 July, 2024

As we grow older, eyesight naturally begins to diminish, and many people develop a condition called presbyopia. This condition affects the capacity to focus on nearby objects, making it difficult to read or perform other tasks that require near vision. Individuals prone to presbyopia tend to begin noticing effects during their 40s. Fortunately, there are several options available for correcting presbyopia, including monovision, also known as blended vision.^[1]

This article reviews what monovision is, how it works, what it treats, the different options available, and how to make the adjustment.

What is Monovision?

Monovision is a vision correction technique that involves rectifying the dominant eye for distance vision and the non-dominant eye for near vision. It encompasses specialized contact lenses, glasses, or surgery.^[2] When correcting for monovision, it is essential to determine which eye is dominant and which is non-dominant to achieve the best results.

The dominant eye is the eye that your brain prefers to use for tasks such as reading, writing, and driving. The non-dominant eye is the eye that your brain prefers to use for functions such as depth perception and peripheral vision. Monovision helps the brain and eyes to achieve clear vision at both distances.

Natural Monovision

Monovision may also occur naturally. Natural monovision happens when one eye may develop the ability for far vision while the other eye is more attuned to near vision ^[3]. It can help prolong the time till bifocals or eyeglasses are necessary to correct presbyopia.^[4]

Natural monovision is not the same as monocular vision^[5], which is vision loss in one eye due to inflammation, vasculitis, damage, or eye disease, such as cataracts, glaucoma, or macular degeneration.

How Does Monovision Work?

Monovision works by modifying the dominant eye for long-distance vision and the other for near-sighted vision. The brain can adjust to this difference in vision and seamlessly switch between the two eyes, providing clear vision at all distances.

The brain adapts to monovision by lowering activity in the primary visual cortex that processes visual information and increasing activity in prefrontal cortex regions involved in attentional focus. These changes occur due to monovision, the blurred vision in one eye that monovision promotes, while the prefrontal cortex adaptations may be working to compensate for the blurred vision.^[6]

Some people may be concerned about the long-term effects of monovision on brain function. However, studies have shown that the brain can adapt to monovision without adverse effects on brain function. Some studies have shown that monovision can improve cognitive function in older adults.

Benefits of Monovision

There are several benefits to choosing monovision as a vision correction option. These include:

• Improved near and distance vision
• No need for reading glasses
• Natural and gradual adjustment to presbyopia
• Can be easily reversed if desired
• Can improve cognitive function in older adults

Risks and Side Effects of Monovision

As with any vision correction option, there are some risks and side effects associated with monovision. These may include:

• Difficulty with depth perception
• Difficulty adjusting to monovision
• Decreased night vision
• Blurred vision at intermediate distances
• Need for frequent adjustments to contact lenses or part-time reading glasses, especially for fine, close-up work or reading for long periods
• Some may have better results with either long or short-distance sight with monovision instead of a balanced result

Is Monovision Safe for Driving?

One of the concerns people may have about monovision is its safety for driving. While adapting to monovision might take some time, it is generally considered safe for driving^[7]. Some people with monovision have no problems driving at night without glasses. However, some people may need prescription glasses while driving at night.

However, it is important to have regular eye exams and to inform your eye doctor if you experience any difficulties with vision while driving.

Candidates for Monovision

Monovision may be a good option for those experiencing presbyopia and looking for a way to correct their vision without the need for reading glasses. It may also be a good option for those who have had LASIK surgery and are experiencing monovision as a side effect. Intraocular lens monovision can be a good option for some people with natural monovision to reduce their risk of developing presbyopia later in life^[8]

Those with the following eye conditions may also benefit from monovision^[9]:

• Weaker corneas with an unusual shape
• Astigmatism
• Very strong prescription for glasses or contact lenses
• Dry eye disease
• Glaucoma
• Maculopathy

However, not everyone is a good candidate for monovision.

Is Monovision Suitable for Astigmatism?

Monovision can be a suitable option for those with mild astigmatism. However, the success rate of Monovision may decrease as the degree of astigmatism increases; hence those with moderate to severe astigmatism may not be good candidates for monovision. It is important to discuss your astigmatism with your eye doctor to determine if monovision is a good option for you.

Who is Not a Candidate for Monovision?

Monovision may not be a good option for those with a significant difference in prescription between their eyes, as this can cause difficulty with depth perception. It may also not be a good option for those with a job or hobby requiring precise depth perception, such as pilots, sports athletes, or artists.

Is Monovision a Good Option for Children?

Monovision is not typically recommended for children, as their eyes are still developing and adjusting to changes in vision. It is important for children to have regular eye exams and to discuss any vision concerns with their eye doctor.

 Monovision Treatment

There are several treatment options available for monovision, including contact lenses, LASIK surgery, and cataract surgery.^[10]

Monovision with Contact Lenses

Contact lenses are a popular option for monovision, as they are easy to use and can be easily adjusted if needed. Several types of contact lenses are available for monovision, including:

• Soft contact lenses: These are the most common types of contact lenses used for monovision. They are comfortable to wear, leaving no impression, and are easily adjustable if required.^[11]
• Rigid gas permeable (RGP) contact lenses: These are a good option for astigmatism patients, as they provide sharper vision. However, they may take longer to adjust to.
• Hybrid contact lenses: These are a combination of soft and RGP lenses and provide the benefits of both types.

It may take some time to adjust to monovision contacts, as your brain needs to adapt to looking with one or the other eye for either distance vision or near vision. Most people can adjust within a few weeks.

Monovision with LASIK

LASIK surgery is another option for monovision. During LASIK surgery, the dominant eye is typically altered to accommodate distance vision and the non-dominant eye for near vision. This correction allows for clear vision at both distances without needing glasses or contacts.

Before undergoing LASIK surgery for monovision, it is crucial to consider the following:

• Your age: LASIK is typically not recommended for those under 18, as their eyes are still developing.
• Your prescription: LASIK may not be a good option for those with a significant difference in prescription between their eyes.
• Your lifestyle: LASIK may not be a good option for those with a job or hobby that requires precise depth perception.

The recovery time for LASIK surgery varies. Most people can continue everyday activities within a few days to weeks. Following your doctor's post-operative care instructions is important to ensure a smooth recovery.

Monovision Cataract or Lens Replacement Surgery

Cataract surgery and lens replacement surgery (refractive lens exchange) are other options for monovision.

During either surgery, an artificial lens, known as an intraocular lens (IOL), replaces the eye's natural lens. This replacement allows for clear vision at both distances without needing glasses or contact lenses. These lenses mimic the eye's natural focusing ability, allowing for clear vision at multiple distances. They offer a more permanent solution for presbyopia correction.^[12]

Cataract surgery is typically only necessary when cataracts are present and are causing vision problems.

If you are experiencing presbyopia but do not have cataracts, surgery may not be necessary.

Mini Monovision

While traditional monovision fully corrects one eye for distance and one for near, mini monovision takes a more subtle approach. This variation, often considered in cataract surgery, intentionally leaves slight nearsightedness in the non-dominant eye.

The benefits of mini monovision include:

• Potentially better distance vision: Compared to standard monovision, you may experience slightly improved distance vision.
• Reduced dependence on glasses: Though you might still need reading glasses for specific tasks, mini monovision may reduce your overall reliance on them.

If you are considering monovision as a treatment option, discuss mini-monovision with your eye doctor to see if it is a suitable approach.

Adjustment and Living with Monovision

Adapting to and living with monovision may initially require some adjustment as the brain learns to switch between the eyes for different distances seamlessly. Temporary visual imbalances and depth perception changes can occur during this period. However, with patience and practice, most individuals adapt well to monovision, finding it a convenient solution for managing presbyopia.

Monovision provides clear vision at both near and far distances, reducing reliance on reading glasses. Despite potential challenges such as depth perception differences, most people can engage in daily activities without significant impact.

Regular follow-ups with an eye care professional ensure optimal vision and address any concerns.

Can monovision be reversed?

Monovision can be reversed^[13]. If you find that monovision is unsuitable for you or no longer wish to continue with this vision correction technique, discuss alternative options with your eye care professional. They can guide you to reverse monovision and explore other solutions that may better meet your visual needs.

Alternatives to Monovision

While monovision is effective for presbyopia, it may not suit everyone. Alternative options are available for clear vision at all distances, providing different approaches to address presbyopia:

1. Bifocal or Multifocal Contact Lenses: These lenses have different zones designed to correct vision at various distances. Bifocal lenses provide distinct near and distance vision sections, while multifocal lenses have a gradual transition between the two. They can be a good choice for individuals who desire clearer vision near and far distances without monovision.^[14]
2. Extended Depth of Focus (EDOF) Contact Lenses: EDOF lenses work by providing a more comprehensive range of clear vision than traditional contact lenses. This effect uses a unique design that allows light to focus on the retina at near and far distances^[15]. EDOF lenses may lower eye strain and improve visual comfort for those frequently switching focus between near and far objects.
3. Progressive Eyeglass Lenses: Also known as no-line bifocals or varifocals, progressive lenses offer a seamless transition between different vision distances. They allow for clear vision at near, intermediate, and far distances without the visible lines seen in bifocals and trifocals. However, they can take some time to get used to, and they may cause eye strain or dizziness for some people.^[16]

Consulting with an eye care professional to discuss alternative options can help to determine the most suitable for your specific needs and lifestyle.

Latest Advancements in Monovision

Advancements in monovision technology continue to improve options for vision correction. Some recent advancements include:

1. Wavefront-guided Monovision: Wavefront technology measures tiny imperfections within the eye that cause vision problems like nearsightedness, farsightedness, and astigmatism. In wavefront-guided monovision, the doctor uses wavefront measurements to enhance LASIK surgery for monovision through personalization^[17]. This customization improves the accuracy of the treatment and minimizes errors, resulting in less quality vision in either eye.
2. Implantable Contact Lenses (ICL): Phakic intraocular lenses offer an alternative to corneal-based correction, providing clear vision without altering the shape of the cornea.^[18]
3. Customizable Multifocal Intraocular Lenses (IOLs): Multifocal IOLs with adjustable near and distance zones enhance vision quality for individuals with monovision.^[19]
4. Enhanced Visual Simulation: Innovative simulation tools allow for realistic evaluation and understanding of monovision outcomes before surgery.^[20]

These advancements offer improved outcomes and options for individuals considering monovision as a vision correction technique. Consulting with an eye care professional will provide insight into these advancements and help determine the best approach for your needs.

Conclusion

The concept of monovision emerges as a promising option for managing presbyopia. With technological advancements, monovision can be customized for better outcomes and improved vision correction. Consulting an eye care professional is crucial in determining if monovision is the right choice for your vision needs.

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