PRESBYOPIA: The Eye’s Inability to Focus as We Age
PRESBYOPIA: The Eye’s Inability to Focus as We Age
What is presbyopia?
Presbyopia (prezbe-ope -ah) is the loss of the eye’s ability to change its focus to see objects that are near. Presbyopia is not a disease, but a part of the natural aging process of the eye that affects everybody at some point in life. It generally starts to appear around age 45.
Why do I need to hold reading material farther away in order to see it?
When we’re young, our eyes naturally have the ability to change their focusing power. However, when we reach our mid 40’s, the ability to change our eyes’ focusing power diminishes. This natural aging change, called presbyopia, turns our eyes from having a dynamic focusing range to something that has a fixed focus in whatever your natural refractive error is.
In individuals who are less than 40 years of age, the eye can be thought of as an auto focus camera. In an auto-focus camera, all one has to do to get sharp pictures is to point the camera in that direction, the auto-focus mechanism kicks in and you get sharp pictures. After age 40, the presbyopic eye can be thought of as a fixed focus camera. Fixed-focus cameras, the most basic of all cameras, have a non-adjustable lens.
What causes presbyopia?
We have a lens inside our eyes which is encircled by a muscle. When that muscle contracts or squeezes, it changes the shape of the lens in our eye thus changing the focusing power of the eye. Our lens is continually growing throughout our lifetime. However, our lens is contained within a capsule making it an enclosed space. So, by about the time we reach our mid 40’s the lens has become significantly dense and no matter how hard that muscle wants to squeeze, the lens just doesn’t want to flex anymore and our eye loses its dynamic focusing ability and becomes a fixed focus camera.
I’m older than 40 and cannot see well at distance, but I can see well up close without glasses. Do I have presbyopia?
Yes. Everybody becomes presbyopic. It’s a natural aging process and it’s impossible to avoid as we age. The situation described is somebody who is myopic (nearsighted). Their eyes natural refractive error causes them to be blurred at distance, but they can see up close.
Most people who are myopic have glasses for distance vision and when they become presbyopic; they simply remove their glasses in order to see up close. However, due to their degree of nearsightedness, they may not be comfortable reading at their eye’s focusing distance. Or perhaps they do not like taking off their glasses to read. This can be solved by using bifocals. Bifocals have the top portion of the lens for distance vision and the bottom portion for reading vision. They can be made both with a line and without a line. Bifocals with a line are the standard bifocals you’re used to seeing. No-line, also known as progressive, bifocals have the reading power in the bottom of the lens transitioned into the lens. Somebody wearing these appear to be wearing regular glasses and not bifocals.
I still see well at distance, but now I need to push reading material further away in order to see it. What should I do?
In this case, you would probably only need reading glasses in order to see up close. Over the counter reading glasses are OK and are good enough to get by. However, prescription reading glasses are always better because they correct for any astigmatism or differences between your two eyes that over the counter reading glasses do not account for.
I used to see well both at distance and up close, but now both are blurry. What’s going on?
In this case, you probably were a little farsighted your whole life and never knew it. When you are slightly to moderately farsighted and young, your eye actually has too little focusing power. Since the lens inside our eye is so flexible when we’re young, the eye can usually compensate for this lack of focusing power by flexing the lens inside the eye even more to allow us to focus up close. This refractive error serves young people well who have it because they are able to function very well without glasses.
As we age and the lens becomes less flexible, it loses the ability to make up for this overall focusing weakness in the eye. So, these farsighted folks all of a sudden realize they need glasses usually in their mid to late 30’s to see well at distance. They usually become fully presbyopic at an earlier age like in their early 40’s and need to wear bifocals or stronger reading glasses in order to see up close. This type of refractive error serves one well when they’re young, but when they become middle aged it becomes a detriment because they end up having no focal plane where they can see clearly without glasses unlike nearsighted folks.
Is there a way to surgically correct for presbyopia?
There is no way to completely surgically correct for presbyopia. However, we do have some techniques and even surgical implants which can really make a great positive impact on patient’s lives.
One technique that we employ is something called monovision. Monovision is where we correct one eye for distance vision (usually the dominant eye) and one eye for near vision (usually the non-dominant eye). It is a compromise since one eye is always blurry which can decrease depth perception slightly, but this is quickly overcome by patients who enjoy this technique as it allows them to be completely free of glasses. We can do monovision either with contact lenses or with LASIK eye laser surgery. We of course do a contact lens trial in monovision first before we offer LASIK eye laser surgery to see if it’s something you like. If it is something you end up enjoying, then permanent correction with LASIK eye laser surgery becomes an excellent option.
Another option we can explore is a multifocal intra-ocular lens. Intra-ocular lenses are what we implant into the eye to replace the natural lens which is usually removed during cataract surgery.
My personal favorite multifocal intra-ocular lens is an intra-ocular lens called the ReSTOR. The ReSTOR is highly engineered to split the light coming into the eye thus producing two focal points in the eye – one for distance vision and one for near vision. This new intra-ocular lens allows most people to completely function well without the use of glasses. This new intra-ocular lens, however, is considered cosmetic and is not covered by insurance carriers. However, Insurance carriers will cover the cost of any medically necessary cataract surgery as well as a standard intra-ocular lens.
For more information on Presbyopia, the ReSTOR® intra-ocular lens, and LASIK please visit my website at www.oahulasik.com. I invite you to make an appointment to see me personally if you have any questions about eye care or would like to discuss any of the presbyopic correcting options described above.
Dr. Michael A. McMann is a Board-Certified Ophthalmologist and Fellowship Trained Surgeon in Cornea, External Disease & Refractive Surgery. His office is located in the Hawai’i Medical Center West – St Francis Medical Office Plaza in ‘Ewa Beach. He can be reached at 677-2733.