Although there are different theories on the causes of presbyopia, it is brought on by a decrease in functionality of the eye’s crystalline lens. The ability to focus on near objects decreases, making it harder to read fine print or work on the computer.
Age and Presbyopia
If you are not using some form of vision correction by the age of 45, your eyes are ahead of the curve. Healthy eyes use a coordinated system to focus between near vision and distance vision. As our eyes age, they gradually lose the ability to change focus and clearly see objects closer up.
As the lens in your eye loses its flexibility, you may exhibit symptoms resembling farsightedness. If you have been farsighted most of your life, you will likely experience the symptoms of presbyopia earlier than a nearsighted person. Both eyes will not always have the same prescription, and you may have one eye in better condition that compensates for the vision loss occurring in the other.
A simple eye exam can diagnose presbyopia. You should have regular eye evaluations. Common symptoms patients describe include headaches, blurred vision and holding a book farther away.
A variety of presbyopia treatments are available including glasses, contact lenses and several different types of surgical treatments. An experienced eye surgeon will typically perform a variety of tests prior to helping you determine which corrective procedure will be best for your needs.
Presbyopia — What is it?
Like gray hair and wrinkles, presbyopia is a sure sign of aging — the word literally means, “aged eyes”. As you move through your forties you may find yourself squinting and rubbing your eyes as you use the computer, or straining to read your book.
Presbyopia is a problem with the eye’s lens. Light entering the eye is refracted (bent) first by the cornea and then by the lens. In a 20/20 (or 6/6) eye, the cornea and lens bend light at the appropriate angles to make it always focus clearly on the retina. The cornea does about 60 percent of the refraction and the lens does about 40 percent.
Loss of Accommodation
After age 40, the lens becomes less able to change its curvature. Accommodation is the lens’ ability to give you clarity at all distances by changing its curvature. Your first indication that something is wrong may be having to hold fine print farther out to see it — sometimes called shortening of the arms. Other symptoms are:
- Requiring brighter light for reading
- Eye strain
The lens curvature is controlled by small muscles called ciliary muscles which are connected to it in a circular structure. When they contract the lens flattens and when they relax the lens steepens.
Possible Presbyopia Causes
The reasons for presbyopia are still unclear, and there are several theories. The most popular is that the lens tissue becomes less flexible and no longer responds sufficiently to the ciliary muscles.
The most common and least expensive treatment for presbyopia is reading glasses. You can go to almost any department store or supermarket or online store and pick up a pair that will magnify fine print. They come in different strengths up to a certain maximum.
- A better idea is to have your eye doctor prescribe you some reading glasses. That way, if you are also astigmatic, the glasses can correct for both conditions.
- You might want a pair of bifocals if you find that your intermediate or distance vision is also becoming blurry.
- You might also want a prescription for some computer glasses, set to magnify text at intermediate distances.
How the eyes work
Eyes are amazing and complex. To understand the nature of vision problems, you must first understand how the eye works. Every part of the eye performs a special function. If any part cannot do its job properly, vision is disrupted.
The Vision Process
In a normal eye, light reflects off objects and into our eyes. It passes through the cornea, pupil and lens and focuses on the retina. The retina transmits the image to the brain through the optic nerve. When the brain receives and interprets the image, we have sight.
The cornea is the transparent outmost part of the eye. Being both clear and curved it is a type of lens. It bends (refracts) light passing through it and is responsible for two-thirds of the eye’s focusing power (optical power).
Iris and Pupil
The iris is the eye’s colored part. It contains the muscles which open and close the pupil, which is the opening in the iris which controls how much light enters the eye. In low light the pupil dilates (widens) to let in more light. In bright light it closes down to reduce any unneeded light.
The lens is behind the pupil and is responsible for one-third of the focusing power of the eye. The lens changes focus between near and far objects, an ability called Accommodation. It does that by changing its curvature between steeper for close objects and flatter for far objects. The curvature changes are done by tiny muscles called ciliary muscles.
On the inside wall of the back of the eye is the retina, which contains photoreceptor cells. Light is focused on these cells, and they send the information to the brain through the optic nerve. The macula is the center of the retina, and gives us our central vision – the perception of fine details and color. The rest of the retina gives us our peripheral (side) vision.
The shape of the cornea and the distance between the cornea and the retina determine whether or not the light will focus on the retina as it should. A misshapen cornea or misshapen eye causes refractive error, meaning that the light is not bent correctly and cannot focus clearly on the retina.
LASIK surgery corrects the corneal shape and this corrects refractive errors by adjusting the focal point to the retina, where it should be.
When the cornea is curved too much or the eyeball is too long, light focuses in front of the retina, and has spread back out by the time it reaches the retina.
Hyperopia (farsightedness) When the cornea is too flat or the eyeball is too short, the focal point is behind the retina, so the light is still spread out when it reaches the retina.
The eye is shaped like a football and creates two focal points, instead of one, making the image blurry.
Causes are not fully known. As mentioned below in detail, it is thought that with age the lens becomes stiff, or the muscles which control the lens become weaker, and accommodation is diminished. Fine adjustments in focus are no longer possible.
This is why people in mid-life develop the need for reading glasses. LASIK surgery for monovision can adjust the focus of one eye for close-up objects and the focus of the other eye for distant objects. With a little practice the brain automatically chooses the proper image.
All the eye structures must be working together properly to accomplish clear vision at all distances. Even the slightest imperfection can impair vision. However, many of these imperfections can be corrected, and clear vision restored.
Theories on Presbyopia Causes
Although everybody will someday suffer some level of presbyopia as they get older, nobody really knows the exact cause of this condition. Starting at around age 40 or 50 your near vision will progressively get worse. There are many theories on causes of presbyopia and many treatments are designed around one of these specific theories.
Hardened Crystalline Lenses
The most widely accepted theory is that aging lenses become harder and lose their elasticity. This is known as lens sclerosis. The tiny ciliary muscles which control the lens curvature become less able to steepen it. This blurs your near vision.
A Clear Lens Exchange replaces the natural crystalline lenses of your eyes with artificial intraocular lenses (IOLs). IOLs like ReSTOR®, ReZoom™, Crystalens® and Tecnis™ help with both distance, intermediate, and near vision problems.
The eye stops growing at around age 10, but the lenses continue to grow through your lifetime. As the lens grows the space between the lens and the ciliary muscles that control its curvature decreases and the ability to focus decreases.
- Laser Presbyopia Reversal is a procedure based on this theory which is being tested. The laser removes tiny pieces of the sclera to make more space.
- Scleral Expansion Bands is another new approach currently being tested. Four tiny bands (2mm x 4mm) are implanted below the sclera’s surface to increase space for the ciliary muscles.
Weakened Ciliary Muscles
Another theory is weakened ciliary muscles that can no longer manage the focusing responsibilities of the lenses.
It is highly possible that all the theories account for the decreased ability to focus on close objects.
Cause of Presbyopia in Simple Language
Presbyopia is the loss of near vision which occurs with age. Presbyopia affects nearly everyone when they reach their mid 40s. Whether you are nearsighted (myopic) or hyperopic (farsighted), or with astigmatism (an oval shaped cornea), you will develop presbyopia.
Presbyopia is caused by factors which affect the lens (crystalline lens) inside your eye. That crystalline lens measures about 3-4 mm in thickness. It changes its shape and thus its focus point when the small muscles within the eye contract. With age, the lens hardens and grows in both diameter and thickness. These 3 factors cause the lens to loose its ability to change shape and focus with the onset of middle age.
Presbyopia results in blurred near vision, and the need to use bifocals, reading glasses, or the need to remove glasses (in some cases) in order to see up close. As presbyopia affects everyone eventually, the best way to handle this condition is to visit your ophthalmologist for yearly eye exams.
Heightened Risk for Presbyopia with Diabetes
Everyone is at risk for presbyopia, or reduced visual clarity, as our eyes age. While the actual cause of presbyopia is not known, there doesn’t appear to be any connection to pre-existing conditions.
Presbyopia appears to occur naturally and independent of your medical history. However, there is some indication that diabetes may lead to a pre-mature onset of presbyopia.
It is not uncommon for vision to degenerate when the body is afflicted with a disease, and severe vision impairment is commonly caused by diabetes. Diabetes is a systemic disease and, if left untreated, can cause permanent blindness. Along the way, however, it can cause similar problems as presbyopia.
The most obvious symptom is the inability to focus clearly on objects that are close. You may also have trouble seeing well in dimly light areas or when driving at night.
The vision problems associated with diabetes and presbyopia will both worsen over time. If you have diabetes and are beginning to notice changes in your vision, you should consult an experienced ophthalmologist to determine if your vision loss is caused by presbyopia or a more severe condition related to diabetes.
Non-Surgical Treatments for Presbyopia
Glasses for Presbyopia
Presbyopia has traditionally been treated with reading glasses. When you reach your 40s or perhaps your 50s, and print starts to look blurry, a vision test by your eye doctor will determine a prescription and custom reading glasses solve the problem.
If you are nearsighted and notice presbyopia beginning, bifocals will be the answer.
If you are farsighted, your near distance glasses prescription will become stronger.
In recent decades drug stores and supermarkets have begun selling reading glasses up to a maximum strength of 2.75 diopters. They are also available online and come in a wide variety of styles and colors and are inexpensive.
However, if you are at all astigmatic you will be better off with prescription reading glasses because they will correct your astigmatism while store-bought glasses will not.
Contact Lenses for Presbyopia
There are a wider variety of contact lenses now than ever before: soft, hard, toric, and monovision lenses. Bifocal contact lenses work similarly to glasses where the top part of the lens corrects distance vision and the lower part near vision. Many people combine both contacts and glasses comfortably.
Monovision contact lenses also correct near and far distance issues. The non-dominant eye is corrected for near vision and the dominant eye for distance vision.
Many doctors prescribe monovision contact lenses to you if you are thinking about undergoing monovision surgery in order to see how well you adapt to that mode of seeing.
Surgical Treatments for Presbyopia
While the exact reasons for presbyopia are unclear, treatments for the condition are continually advancing. More surgical treatment options for presbyopia are becoming available as new research is enhancing our understanding and the technology is advancing.
Monovision using glasses or contact lenses corrects the dominant eye for distance vision and the non-dominant eye for near vision. With LASIK Monovision, the eyes themselves can be corrected in a similar manner.
Monovision does take some getting used to and your eye doctor may prescribe monovision contact lenses or glasses prior to scheduling LASIK. That will give you a trial run. LASIK monovision is permanent.
Conductive Keratoplasty (CK)
Hyperopic and presbyopic patients may benefit from this procedure which uses low frequency radio waves to fine-tune the corneal curvature. The treatment steepens the cornea by shrinking connective tissue around its periphery.
The steeper corneal curvature can bend light rays coming from nearby objects more sharply and focus them on the retina.
CK is a safe and effective procedure with few risks. It will not leave any scars and does not cause dryness in the eyes.
Refractive Lens Exchange (RLE)
In this procedure, also called Clear Lens Exchange, your natural lens is completely replaced with a clear, artificial lens called an intraocular lens or IOL. RLE is primarily used to replace the cloudy lenses of cataract patients, but presbyopes are also benefiting from this procedure. There are several types of IOLs available, depending on your specific requirements.
Other less well-established surgical procedures include:
- Surgical Reversal of Presbyopia (SRP)
- Anterior Ciliary Sclerotomy (ACS)
- Laser Presbyopia Reversal (LAPR)
As with all surgical procedures, there are inherent risks involved. In some cases, the procedure may not work as expected and additional corrective surgery would need to be scheduled.
Surgery also leads to greater risk of retinal detachment later in life. It is best to discuss the risks with your doctor prior to undergoing any surgical treatment for presbyopia.
The CLE Procedure
Your eye surgeon will make a very tiny incision outside the visual field and insert a probe. Ultrasound is transmitted to the lens to disintegrate it. This makes it easy to remove with gentle suction.
Through the same incision your surgeon will insert the IOL and position it in the same membrane that previously held the natural lens. The incision is closed and a protective shield placed over the eye. Each eye is done in a separate surgery.
Recovery takes one to two weeks from each procedure. You will immediately see more clearly and can resume many activities quickly. There will be some swelling at first but it will subside quickly. Your eye surgeon will give you instructions for how to care for yourself and when you can resume work.
As with all surgical procedures, there are risks.
- Retinal detachment
- In some cases of cataracts, the lens membrane will later develop some cloudiness and a second surgery will be necessary to treat that
By choosing an experienced and reputable eye surgeon who screens his surgery patients rigorously, you will be minimizing your chances of any post-surgical complications.
What is Monovision?
A person with healthy eyes has binocular vision, meaning that each eye sees a given set of images, depending on where you are gazing, and these two sets of images are slightly different.
That is because the two eyes are in slightly different positions on the face and see the same objects from two slightly different angles. The brain receives these two sets and automatically merges the data.
Monovision refers to one of those two sets of images. If you cover one eye you are using monovision with the other. A monovision treatment corrects one eye for near vision and the other for distance vision. Presbyopic eyes see well in the distance so one eye can be left as it is and the other corrected for near vision.
Now the brain is receiving two much more different sets of images. It must learn to give precedence to one for near vision and the other for far vision.
Monovision With Contact Lenses
Contact lenses can be designed to give you customized monovision and this can be a long-term presbyopia treatment. It can also be a trial to see how well you adapt to monovision before having LASIK monovision.
As your vision continues to deteriorate from presbyopia, the contact lenses can be updated.
Surgical Monovision Correction
LASIK monovision is a permanent correction.
- If you have 20/20 eyes, it corrects the non-dominant eye for near vision and leaves the dominant eye as is for far vision.
- If you are nearsighted with presbyopia you would have the dominant eye corrected for distance vision.
- If you are farsighted with presbyopia you would not need one eye corrected for distance vision but would have the non-dominant eye corrected for near vision.
Eye Exercises for Presbyopia
Presbyopia is a natural part of the aging process. It is a change in the eye’s ability to focus on objects close to you. It is a common misconception that eye exercises may eliminate the negative impact that aging has on the eyes.
Sadly, there is no medical evidence to support eye exercises as an effective cure for presbyopia. However, there is some indication that eye exercises may help delay the need for corrective lenses in some people.
According to Harvard Medical School Family Health Guide, if you practice eye exercises very faithfully, you may be able to put off having to wear glasses or contact lenses for a little while. You cannot prevent the effects of presbyopia as you age with just eye exercises, though.
The lens of the eye stiffens as you age, allowing less flexibility when you shift your vision from a close object to one at a distance. You may notice eye strain that leads to headaches from reading or working at a computer all day. You may also notice that you are squinting more to read clearly.
Although eye exercises don’t stop your eyes from aging, there are a variety of methods for maintaining healthy eyes including several surgical treatment options.
In addition, there are a few things you can do to help eliminate some of the side effects associated with eye strain and headaches. One of the most helpful tips is to take regular visual breaks. Here are some simple things you can incorporate into your daily routine:
- Rest your eyes occasionally throughout the day by closing them and relaxing
- Pause from staring at the computer screen to focus on an object at a distance for about 20 seconds
- Focus on relaxing your shoulders and neck with slow head rolls