In The Optics of Vision – Part 9, we learned about the function of the crystalline lens. But as I pointed out towards the end of the lesson, the crystalline lens gradually stops functioning. This results in the condition we’re going to discuss in this lesson called Presbyopia.
This being the last lesson of The Optics of Vision course, it will continue to build off of everything taught so far. I strongly recommend making sure that you have read every previous lesson before reading this one.
Recall from Lesson 9 that crystalline lens allows us to see clearly up close by automatically adjusting its curvature to give just the right amount of focusing power for the distance the eye is looking at.
Quick Accommodation Recap
Looking in the distance (further than 6m/20ft)
The crystalline lens is at rest (as flat as possible)
Takes no effort
Looking at intermediate distances (~1m/40”)
The crystalline lens ‘accommodates’ (gets more curved)
Requires minimal effort
Looking at near distances (~30cm/12”)
The crystalline lens accommodates even more (gets even more curved)
Requires significant effort
Looking at extremely near distances (~15cm/6”)
The crystalline lens maximally accommodates (gets as curved as it can)
Requires maximal effort
Takeaway: Without accommodation, we cannot see clearly up close.
Requirements for Accommodation
Functioning accommodation requires 2 things:
A flexible crystalline lens
Functioning ciliary muscles (the mucles that act on the crystalline lens)
For the vast majority of people, the crystalline lens is very flexible and the ciliary muscles are very strong in the first 4 decades of life (~ age 0 to 40 yrs). During this time, accommodation works so well that most of us don’t even know its happening – and thus take it for granted.
After the age of 40, the crystalline lens becomes stiff to the point that the ciliary muscles can no longer flex it. That’s when accommodation begins to fail. This is what is called presbyopia.
What is Presbyopia?
Presbyopia begins when accommodation starts to become sluggish due to changes in the crystalline lens and ciliary muscle. When presbyopia kicks in, our vision up close becomes blurry. It’s often noticed for the first time when attempting to make out small print up close such as the kind found of medicine bottles. From there, it gradually gets worse year after year until eventually, nothing within a couple of arm lengths is clear.
Presbyopia FAQ
Who Does Presbyopia Affect?
Everybody will eventually be affected by presbyopia.
When Does Presbyopia Start?
Presbyopia starts at different times for different people. On average it is at age 40, but it it not unusual for it to start in the late 30’s or even into the mid 40’s for some people.
In addition, the prescription one has for distance viewing can also impact when the symptoms of presbyopia are first felt. People are farsighted tend to notice the symptoms of presbyopia earlier than people who are nearsighted (especially if the nearsightedness is very low).
What Are The Symptoms of Presbyopia?
In the early stages (late 30’s to mid 40’s), presbyopia will cause very detailed objects that are held quite close to the eyes to be blurry, as well as difficulty seeing up close in dim lighting. Most near viewing tasks such as reading and computer work are still possible in this stage.
In mid stages (late 40’s to mid 50’s), anything held in one’s hands will be difficult to see clearly. In addition to the blur, persistently trying to ‘fight’ the blur can lead to eyestrain and headaches. Reading is very difficult in this stage but computer work is still possible.
In the late stages (late 50’s and onwards), everything within two arm’s lengths or so will be blurry. Both reading and computer work will be impossible without the use of corrective lenses.
What is the Treatment for Presbyopia?
The treatment for presbyopia is simply to wear glasses or contact lenses for reading/computer work. In the eye care industry, the things we do that require us to see clearly up close is called near work. Glasses that help with near work are called reading glasses.
Reading glasses can be as simple as a pair of glasses that are worn for near work, and removed when looking in the distance. However, for people who need glasses for the distance as well, a different type of glasses may be required. You will have heard of these as bifocal glasses.
Bifocal glasses hold lenses that carry the distance prescription throughout the entire lens except for a small segment at the bottom which holds the reading prescription. Most new presbyopes (people with presbyopia) associate bifocal glasses with their parents or grandparents and are resistant adopt them. That’s why bifocals are very rare nowadays. Instead, the go-to type of glasses for presbyopes are called progressives.
Other common names for progressive lenses are no-line bifocals, varifocal lenses & PALs (progressive addition lenses).
Progressive glasses have multiple prescription within different places in the lens. There is a distance prescription, an intermediate prescription for computer monitors and a reading prescription for hand held reading material. However some people can see well in the distance without glasses an only need help with computer work and reading. For these people there is a specialized type of progressive lenses called office progressives.
As a completely different alternative for people who don’t like glasses at all, there are contact lenses that can – to a certain extent – help people see in the distance as well as up close for reading. These are called multifocal contact lenses.
Can You Reverse Presbyopia Naturally?
Unfortunately, there is no natural cure for presbyopia in the form of eye exercises, eye drops, supplements or otherwise.
From time to time there are claims of this or that exercise program that can reverse the effects of presbyopia. Though I have not seen any concrete evidence for these methods, it would be great if they actually worked. if you have tried them, I would love for you to share your experience in the comments below.
Can You Reverse Presbyopia With Medication?
There is currently no medication to cure presbyopia.
Can Presbyopia be Reversed Surgically?
Yes and no.
When someone has their cyrstalline lens surgically removed, they are technically no longer presbyopic. Instead, they become pseudophakic, which is essentially the same thing. Unless…the surgically implanted lens that replaces the crystalline lens is something called a multifocal intraocular lens.
Additionally, there is a laser surgery for presbyopia that is producing very good results for some people. The technique is called PRESBYOND and is offered at most laser vision correction centers.
Note that PRESBYOND does not affect the crystalline lens or ciliary muscles in any way. It reshapes the corneas in order to compensate for the loss of function of the crystalline lens/ciliary muscles.
Summary
Presbyopia is the inability of our eyes to focus on near objects due to the loss of accommodation. It’s a normal age-related change and will happen to everybody once they enter their 40’s. The best treatment for presbyopia depends on many factors such as your underlying distance prescription, occupation, lifestyle, etc.
Congratulations!
If you’ve read through lessons 1-10 and you understand the material presented, you now know a lot about the eyes, optics, and how vision works. Congratulations on making it through! It really shows your dedication to becoming successful in the eye care industry.
With all of this knowledge in the bank, the next step of your training is to take The Lost Contact’s course on Optical Dispensing. I’ll see you there!
