Behind the Lens: Bifocals, Monovision, Progressive Lenses, and Their Unexpected Impacts

Did you know your glasses do more than just improve your sight? When you slip on a pair of bifocals, use monovision contacts, or look through progressive lenses, you are not just correcting your vision – you are impacting your posture, influencing your brain, and subtly changing your interactions with the world – and it might not always be in a positive way. I am writing this blog to bring awareness as I have helped many of my clients over the past decades to overcome their pain and postural issues which were fully or partially created over time due to their vision correction methods. The majority experienced back and neck pain but it also included other areas of the body, and depth perception challenges which can lead to a higher incidence of falls to name just a few. Depending on the type of vision correction your brain function might be impacted as well. Let’s dive in to understand the differences and the various impact on brain function and posture.

Bifocals

First introduced by Benjamin Franklin, bifocal glasses have been a boon for those grappling with presbyopia (age-related farsightedness). These lenses are designed with two distinct areas – the upper part aids distance vision, while the lower part assists with near vision.

Bifocals are great for those who need help seeing both near and far, cutting out the need for two separate pairs of glasses. Once you adjust to them, bifocals are easy to use - you simply look through the top or bottom of the lens, depending on what you're doing. It can take some time to get used to bifocals. There can be an initial phase of discomfort or dizziness as your brain adjusts to the sudden change in focus. The division in the lens can restrict the field of view. This can be particularly problematic for tasks that require intermediate vision, such as working on a computer.

Effect of Bifocal on Posture and Brain Function

The divided lens of bifocals can lead to a habit of tilting the head back to see close objects through the lower part of the glasses, and forward to see distant objects through the upper part. Over time, these repetitive movements can cause neck strain and poor posture. Furthermore, the visual system and the brain need to continuously adapt to the abrupt change in focus, which can be cognitively demanding. The sudden change in visual focus can impact depth perception and spatial awareness, particularly when shifting focus between the near and far zones. Tasks such as walking down stairs can initially be challenging when starting to use bifocal lenses. This issue places additional cognitive demand on the brain as it recalibrates to new visual cues. Bifocal lenses can also cause peripheral distortion, especially in the area around the line separating the two sections of the lens. This distortion can disrupt the user's spatial awareness, causing discomfort and confusion.

Monovision

Monovision is a method used to correct presbyopia by having one eye corrected for distance and the other for near vision, either through contact lenses or refractive surgery. With each eye specialized for a different distance, monovision allows for a range of clear vision without the need for bifocals or progressive lenses. Monovision is often a preferred choice for people with an active lifestyle as it eliminates the need for constantly switching between different pairs of glasses. Because each eye is corrected for a different distance, depth perception can be affected, making tasks like driving or playing sports challenging. Similar to bifocals, there's an adaptation phase while your brain learns to switch between eyes for different tasks.

Effect of Monovision on Posture and Brain Function

With monovision, the brain must continuously choose which eye to prioritize based on the distance of the object being viewed, leading to increased cognitive load. In monovision, one eye is corrected for distance vision and the other for near vision. This setup can lead to a reduction in depth perception because binocular vision (where both eyes work together) is key to perceiving depth accurately. This additional challenge requires the brain to work harder to interpret depth information. The brain is designed to collate images from both eyes to create a single, unified image. In monovision, because each eye is seeing at a different focus, the brain has to manage the potential conflict between the images each eye is sending. This issue can lead to initial disorientation and confusion, requiring additional cognitive effort to resolve the discrepancy, postural changes, muscle tightness, and more.

Progressive Lenses

Progressive lenses, also known as no-line bifocals, provide a smooth transition from distance correction at the top to near correction at the bottom. This seamless transition offers a more natural and comfortable viewing experience. Progressive lenses eliminate the need to switch between different pairs of glasses for near and far vision, providing convenience and a wide range of vision corrections within a single lens. Once you adjust to them, progressive lenses can provide a more comfortable viewing experience, as they eliminate the abrupt change in focus that you encounter with bifocals. It can take some time to get used to progressive lenses. During this period, you might experience some distortion on the periphery of your vision. The intermediate vision area in progressive lenses can be narrow.

Effect of Progressive Lenses on Posture and Brain Function

Progressive lenses offer a solution that can alleviate some of the issues related to posture and cognitive load. They reduce the need to tilt the head back and forth, which can lead to neck strain. Additionally, they eliminate the abrupt change in focus that occurs with bifocals, reducing the cognitive load on the brain. Progressive lenses may cause peripheral distortion because the lens power changes gradually from top to bottom. This distortion can result in a 'swim' effect, where objects in the peripheral vision can appear to move. This 'swim' effect can be disorienting and mentally demanding until the brain adapts to interpret these visual signals effectively. Unfortunately for some, they may never fully adjust to it and feel off balance, tight, and less grounded. Progressive lenses can also potentially affect spatial perception due to the differing corrective powers in the lens. This could initially cause difficulty with tasks such as descending stairs, where depth perception is important. The brain needs time to recalibrate and interpret the new visual cues, which can add cognitive load.

Vision is complex and varies significantly from person to person. The strategies you use to enhance your vision can have unexpected effects on your posture and brain function. Whether you're considering bifocals, experimenting with monovision, or exploring the seamless transition of progressive lenses, it's crucial to pay attention once you start using them and how your body and brain react to them. In my experience, monovision has been the most challenging method for the body and brain to adapt to and causes the most negative effect regarding aches and pain. In the end, the goal is to find a solution that provides clear and comfortable vision, supports healthy posture, and facilitates optimal brain function. Sometimes it means accepting the hassle of switching between two pairs of glasses and/or vision and postural training. There is no ‘one size fits all’.