Presbyopia
Children have incredibly good near vision and can read print placed only a few centimetres from their eyes. By the time you have reached 30 years of age, you can still read small print; however, you will need to hold it about 20 cm from your eyes. By your early 40s, you may need to hold the print at arm’s length, or your arms may not be long enough!
What is Presbyopia?
This loss of close vision is called presbyopia.
It is not fully understood, but it affects all of us and is a natural consequence of the ageing process.
What are the effects of Presbyopia?
Presbyopia, if uncorrected, can be debilitating and may lead to:
- Loss of confidence at work or in situations where you need to carry out near-vision tasks, such as reading or measuring.
- Difficulty carrying out your job properly.
- Possible loss of employment if you are unable to perform required tasks.
- Inability to operate machinery or read instructions, which could result in a serious workplace accident or injury.
What are the root causes of Presbyopia?
As we age, the collagen fibres in our skin become less springy and less elastic. This leads to a change in the appearance and feel of our skin, such as wrinkles and sagging.
You may have noticed that when you pinch the skin of a younger person, the skin immediately springs back. If you do the same to someone in their 40s or 50s, the skin takes much longer to return to its original condition.
Getting back to your eyes, before you are born, your eyes begin as part of your developing tissue before eventually differentiating into the clear, transparent tissue of the cornea and lens.
So, there is a close link between our skin and our eyes.
Crystalline Lens
The part of your eye that allows you to focus on things up close is a small, clear disc located just behind your iris, or the coloured part of your eye. It is roughly the size and shape of a Panadol tablet.
This small disc is called the crystalline lens, and it allows you to focus on whatever you want to look at, whether it is 10 metres away or only a few centimetres from your face.
The crystalline lens does this by flexing and changing its shape in response to signals from the brain. We can focus or defocus our crystalline lens. It is, in effect, like the zoom lens in a very expensive camera.
The lens is vital to our ability to see things clearly at any distance, from far away to up close. It is constantly working and gives us incredibly sensitive and flexible control over our vision.
Like the rest of our skin, the lens is made of collagen. However, it is a very special type of collagen. Unlike the skin covering the rest of our body, which is opaque, the crystalline lens is crystal clear. It is an amazing structure, as it not only allows the passage of light to the retina, but also finely controls the focus of the images that we see.
So Why Does This Lens Stop Working as We Get Older?
Sadly, as mentioned before, the collagen in the lens, like the collagen in our skin, loses its elasticity over time. After 40 years of age, it rapidly becomes less flexible and cannot zoom in and out of focus as effectively.
By the age of 60, the lens has almost zero flexibility.
Presbyopia is caused by the loss of lens flexibility.
A Major Problem Facing Today’s Ageing Workforce
Presbyopia, if untreated, can result in:
- Loss of confidence when reading measurements.
- Poor work performance.
- Loss of employment if you are unable to do the job.
- The potential for serious workplace accidents and resulting injuries.
How Can This Problem Be Addressed?
There is no medical treatment available to stop or reverse presbyopia.
You need to see your optometrist. They will give you a choice of treatment options. These options may involve one, or a combination, of the following:
- Reading glasses. Half-eye or larger frames can be effective, but they have a very limited range of focus. You may find yourself craning your neck forward to bring print into focus 80 cm away.
- Bifocals. Bifocals have been around for a long time. The first bifocal is thought to have been invented by Benjamin Franklin about 200 years ago. The benefit of bifocals is that they give you distance and near vision in one pair. The disadvantage is that they have a line across the middle, which some wearers find annoying. Another issue with bifocals is that they do not provide intermediate focus at 80–100 cm from your eyes, which is where most computer monitors are usually positioned.
- Progressive addition, multifocal or invisible bifocal lenses. These give you continuous focus from distance to near, and they look like normal lenses with no lines. Disadvantages can include peripheral field distortion and a narrower area for reading. They can also cause straight lines to look curved, which can be an issue for people in the building industry.
Presbyopia Summary
Other treatment options include extended-focus reading glasses for computer users, contact lenses and laser surgery, which we will discuss in a later article.
Readers, bifocals and progressive glasses are all great options; however, we recommend that you see your optometrist for advice on which option, or combination of options, best suits your needs.
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