Presbyopic, Bifocal Contact Lenses Are For You

The bifocal lenses are very hard to come by. At one point in history, they were pulled off from the shelves due to ineffective designs. Now, however, new technology has been innovated which helped put these lenses back in the market. 

Although, very few and specific people can only benefit from bifocals, and these selected group of people are those who are presbyopic.

In this article, presbyopic will know how bifocals work for their particular eye condition, how they are beneficial for them, and the different types of bifocals that they can refer to.

Presbyopia and Presbyopic Defined

Presbyopia or what is also known as “short arm syndrome” is the eye condition where small or fine details appear blurry.

You have to stretch out your arm to see the objects you’re carrying more clearly.

People who develop presbyopia are those over the age of 40. Slowly and gradually, as they age, they will start to notice that their near vision gets blurry and they’ll find it difficult to focus on things up close.

This happens because every year as you age, the elasticity of the lens inside each of your eye becomes rock-hard.

As a result, your eyes lose its ability to focus on nearby objects because light is now being focused behind the retina rather than on top of it.

A Basic Break Down on Bifocals

Generally, it is significantly hard when you prescribe bifocals, and the success rate of these lenses are very low.

This is presumably because various designs and types of bifocals are available. 

As has been indicated multiple times by a large number of authors, bifocals should only be prescribed with the consideration of the history of contact lens used. 

Bifocal contact lenses aid in the correction of presbyopia through its vision correcting properties for both distance and near sight.

These contacts accommodate multiple prescriptions on a single lens to help you see clearly at a range of distances.

Classification of Bifocal Contact Lenses

To further understand these lenses, here are the classification which best illustrate each type’s function, specifications, and utilization.

Bifocal Contact Lenses are classified into two types:

• Alternating Vision 

The alternating vision type is also referred, to a selective few, as the translating vision. Specific wearers are able to view object either at a distance or close by way of the upward and downward motion of the visual axis, as with bifocal glasses, while both distant and near images are formed on the retina simultaneously along with simultaneous vision. 

The upper and lower parts of the lens, respectively, stands to be the support for the distant and near vision alike the lens of bifocal glasses.

Which is why, it is especially necessary to move the visual axis downward for near vision, and image jumping tends to occur when crossing the boundary between the two parts of the lens. 

To keep it stable and steady, preventing it from rotating around, the methods of centering is important, truncation, and a ballast prism is attached to the lower part of the lens.

• Simultaneous Vision

All the while, simultaneous vision is referred to as the segmented lenses. Simultaneous vision bifocal contact lenses are classified into refractive and diffractive types. 

Refractive lenses

The central and peripheral parts of the lens are used for distant and near vision, respectively, while their functions are reversed in the Alges type of lens.

The power changes successively from the center toward the periphery. Light from both distant and near objects forms images on the retina simultaneously, hence the term.

The wearer sees both of the images thrown in front and the brain decides which image should be selected.

Take the way we differentiate the sounds we want to hear from background noise, this process is just like that. 

Roughly, you can’t experience any rotation problem with this type of lens. However, since vision is influenced by the tilt or deviation of the lens, centering and appropriate fitting are important, as mentioned in the previous section.

Diffractive lenses

There is a concentric groove on the posterior surface of these lenses, which causes diffraction of some of the incident light rays.

The image of a distant object is formed by refraction at the center of the lens, while that of a near object is formed as a primary diffractive image in the circular diffractive zone on the inner surface of the lens.

However, the contrast of diffractive images is poor and glare is often a problem.

How do Bifocals Work for Presbyopic?

Bifocal contacts contain two different focal points for your distance and reading prescriptions.

Bifocals have been around for many years, but it wasn’t until recently that they became popular again. Older bifocal designs didn’t satisfy many people which led to more frustrations among wearers and prescribers alike.

Today, with the advent of new technology, more successful designs have been produced with a wide array and greater variety of designs.

It’s expected that not all design best suits you, or what you personally prefer. If that is the case, here are some that you can consider.

Your practitioner might also implement these alternative ways:

Monovision 

Monovision involves using single-vision lenses to put your near prescription on one eye and your distance prescription on the other.

Modified monovision

Modified monovision uses a single-vision lens on one eye and a multifocal lens on the other.

If nothing ever works for you, you can always go back to the traditional prescription glasses.

They are proven to be an effective alternative, and you can wear eyeglasses with progressive lenses over your contact lenses when needed if monovision don’t provide you any adequate vision no matter the distance.

Many contact lens wearers prefer wearing glasses with progressive lenses rather than reading glasses. The common reasons are the following:

• Full-size eyeglasses with line-free progressive lenses looks more youthful than store-bought “readers.”
• Progressive lenses can correct any mild residual astigmatism or other refractive error that can never be fully corrected or managed by your contacts. Hence, eyeglasses with progressive lenses may give you sharper vision for specific activities like reading with a dim light on.
• Progressive lenses allow you to see clearly at all distances without having to constantly put on and take off reading glasses.

Qualifications for Bifocal Contact Lens

Two factors that your eye care practitioner will consider in choosing a bifocal contact lens are pupil size and your “add,” or near prescription.

There are no hard and fast rules. However, at the end of the day, it will always be what your practitioner says and what they deem fit for you and your needs.

You may need to try bifocal contact lens designs before finding the one that’s right for you. Many practitioners offer free trial lenses to help you through the process.

Keep in mind that although trial lenses may be free, your doctor will still charge you for the multi focal contact lens fitting process, which typically is more time-consuming, and therefore more costly than a regular contact lens fitting.

See your eye doctor to determine if bifocal contact lenses make sense for your needs and to identify the best lens for you.

Ultimately, your contact lens prescription will include the following specifications. These are what makes up for your bifocal lenses that will be specially tailored for you: 

• Specific brand of contacts
• Power (or sphere)
• Base curve
• Diameter
• ADD power

If you are prescribed rigid gas permeable contacts, your prescription will also include color and dot details.

All contact lenses fit differently for every specific patients and are made of different materials. If you are going to try lenses that have not been prescribed, you may encounter the worst cases possible: discomfort or eye infection.

So, it is important to have a valid contact lens prescription to ensure that you’re purchasing products are suited for your eyes.

References:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699779/

https://www.coastal.com/thelook/how-do-multifocal-bifocal-contacts-work/

https://www.allaboutvision.com/contacts/bifocals.htm