The eye, like a camera, has to adjust its focal power for the distance of different objects. For example, if you are watching a television placed 12 feet away, your eyes’ focus is set for that object distance of 12 feet. Now, if you begin reading a newspaper held at 16 inches, your eyes’ focus must adjust for the object distance of 16 inches. If your eyes remain focused for 12 feet the newspaper held in your hand will be blurred and you won’t be able to read it.
Presbyopia occurs when an eye can no longer adjust its focus for short object distances. It is one of the most common reasons why people get an eye exam and often the most common reason for getting glasses.
Presbyopia is often noticed in your early to mid forties. Most people feel that it happens all of a sudden. In fact, it happens very slowly over many years. The focus system of our eyes is made up of two parts. The first is the cornea, the clear front-window of the eye. It supplies about 75% of the eye’s focus power. The second is the clear lens which is found just behind the pupil. The clear lens supplies about 25% of the eye's focus power. The lens is contained within an elastic bag called the lens capsule, which contracts or expands to thicken or thin the lens to focus on the near objects. This can happen because the lens is very supple and it is easy to change its shape.
So what can you expect to notice?
Among the signs and symptoms are eyestrain, tired eyes, blurred vision while doing fine, detailed work up close, and a need to hold objects further away in order to make them clear. In the early stages, some may have clear vision up close but will notice blurry distance vision right after a prolonged reading spell that may take a few minutes to clear. Some people may notice blurring of close vision first thing in the morning, which goes away after a few minutes. Others will have good close vision early in the day but will notice more blur as the day goes on.
So what can be done about presbyopia?
The most common answer is to get reading glasses or multifocal lenses. The lens power of the reading glasses makes up for the lost focusing power caused by the lost flexibility of your natural lens. You will find reading glasses work great for the close vision. But, when you look up and no longer need the extra focus power, they will blur out your distance vision and will have to be removed. This, of course, causes a need to handle your glasses a lot. Reading glasses can be made in regular eyeglass frames or in half-eyes. Half-eyes are made to be worn half way down the nose and enable you to see in the distance by looking over the top of the glasses. Over-the-counter reading glasses can be purchased without a prescription in many drug stores. These can help if you don't need glasses for your distance vision and both eyes require the same lens power.
Multifocal glasses can get rid of the need to take the glasses on and off. The eyeglass lenses are divided into two or more parts. You simply look through the top part to see in the distance and look through the bottom part to see up close. These are useful if you need glasses for your distance vision as well as the near vision. These can come as bifocals, trifocals, or progressive add lenses (also called no-line bifocals). Your doctor or optician can help you decide which type is right for you.
What about the contact lens wearer who becomes presbyopic?
There is no need to quit wearing contacts. There are three options. First, wear reading glasses over the contact lenses. Second, try bifocal contact lenses. They're not for everyone but there are many designs, and one may work for you. Third, try monovision. With this technique, a contact lens is used to set the focus for one eye for the distance while another contact lens is used to set the focus of the other eye for near. Again, this is not for everyone but seems to work about 50% of the time.
If you happen to be nearsighted you have one other method of fixing presbyopia. Simply remove your glasses for reading. The eye’s focus for nearsighted is already set for up close. Therefore you can see to read clearly without having to accommodate. Many nearsighted people who have needed glasses for distance for years are happy to find out that they can remove their glasses for reading when others their age are having to put glasses on to read.
Common misconceptions about presbyopia:
1. With the right eye exercise, presbyopia can be cured without the use of
reading glasses. Not true...Presbyopia is caused by the loss of pliability of
the crystalline lens. This is aging of tissue and cannot be fixed by eye
2. The use of reading glasses will speed up the loss of focus. Not true...Aging
is the only thing that causes further loss.
3. A lot of reading will cause presbyopia to occur at an earlier age. Not
true...Again, the only thing that causes presbyopia is the loss of lens
pliability with increasing age. Because of genetic differences, presbyopia
will develop at different rates. For example, you may need bifocals at age
43 and your spouse may need them at age 41 and a friend may need
them at age 45. This is due to genetics and not because one person used
his eyes more or less.
4. Using over-the-counter reading glasses will harm your eyes. Not true...
Glasses will not cause harm to your eyes. Even if the prescription is
wrong, the worst that can happen is headache or eyestrain that will go
away after taking off the glasses. Over-the-counter reading glasses
cannot be used by each person, but if your prescription is compatible with
them, they can be an easy and cheaper alternative to prescription glasses.
The Spanish version of this Health Facts for You is #7305.
The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Any duplication or distribution of the information contained herein is strictly prohibited.
Last Updated: 07/10/2013
Copyright © 07/10/2013 University of Wisconsin Hospitals and Clinics Authority. All rights reserved. Produced by the Department of Nursing. HF#5038
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