Presbyopia (pronounced prez-bee-oh'-pee-ah) is the normal age-related loss of ability to focus on near objects. The term comes from Latin words that mean "aging eyes". Most people begin to experience presbyopia in their early 40s - but some people notice it earlier and others later. Symptoms of presbyopia include eyestrain when reading, difficulty keeping reading material in clear focus, an inability to read small print, and the need to hold reading material farther away to see it clearly. Most people begin to notice these problems when they reach their mid-forties.
What causes presbyopia?
Presbyopia is caused by the thickening and loss of flexibility of the crystalline lens inside the eye.
When we view distant objects, the crystalline lens is in a relaxed position. But when we want to see near objects clearly, the lens must change shape to add focusing power to the eye. This process is called Accommodation. Here's how it works:
- The crystalline lens is held in place in the eye by a focusing muscle that surrounds it. This muscle is called the ciliary muscle. The lens is attached to the ciliary muscle by tiny fibers called zonules.
- When the ciliary muscle contracts, the zonules increase tension on the lens. This changes the shape of the lens, increasing its curvature and focusing power.
As a person gets older, the crystalline lens thickens and loses its ability to change shape. When this happens, the lens can no longer add sufficient power to bring near objects into clear focus.
Though the crystalline lens begins losing some of its flexibility in early adulthood, most people don't experience the symptoms of presbyopia until their 40s.
How common is presbyopia?
Since presbyopia is a normal aging change in the eye, virtually everyone experiences it as they reach their forties and fifties. Nothing that can be done to prevent it.
What are the symptoms of presbyopia?
The symptoms of presbyopia are similar to those of farsightedness. However, farsightedness occurs at an early age and is related to the shape of the cornea and the length of the eyeball. Presbyopia occurs later in life and is due to an age-related loss of flexibility of the lens in the eye.
Symptoms of presbyopia include:
- Eyestrain, headaches or fatigue when doing close work.
- Difficulty changing focus from distance to near.
- Blurred vision at a normal reading distance.
- Holding reading material at arm's length to see it clearly.
How is presbyopia detected?
Visit your eye doctor if you are having trouble seeing clearly up close. During the course of a comprehensive eye exam, your Optometrist or Ophthalmologist will check for presbyopia and determine which lenses give you the most comfortable reading vision.
How is presbyopia treated?
Presbyopia is usually treated with eyeglasses. But it also can be treated with contact lenses and Refractive surgery.
- If you don't currently wear corrective lenses
If you don't need corrective lenses for distance vision, reading glasses are usually your best option to correct presbyopia. Reading glasses contain Single vision lenses that are prescribed for a normal reading distance. Your distance vision will be blurred through reading glasses, so you will have to remove these lenses to see clearly across the room.
If you want to see clearly up close and far away at the same time, consider half-glasses. These reading glasses have a shorter frame so you can look over top of the lenses to see clearly across the room.
Bifocals or Progressive lenses can also be used for reading glasses, but these lenses have a much smaller lens area for reading than single vision reading glasses.
- If you currently wear eyeglasses
If you already wear eyeglasses for distance vision, changing to bifocal or progressive lenses will correct presbyopia and provide clear vision at all distances. Bifocal lenses offer a wider reading zone, but many people dislike the visible (and age-telling) line in bifocal lenses. Bifocal lines also cause an abrupt change (or "jump") in your vision when your eye moves across the line.
Progressive lenses have no visible line and offer a gradual progression of power in the lens for smoother transitions between distance and near vision. Though the reading zone in progressive lenses is slightly smaller than the reading zone in bifocal lenses, most presbyopes prefer progressive lenses.
(For the greatest comfort and satisfaction, ask your professional Optician for help to determine which type of multifocal lenses - bifocal, trifocal, or progressive - are best-suited for your needs.)
- If you currently wear contact lenses
Most contact lens wearers purchase reading glasses to wear over their contact lenses to correct presbyopia and restore their near vision. But another option for contact lens wearers is to have their contact lens prescription modified for Monovision (see below).
Many contact lens wearers choose to have their prescription adjusted for monovision to correct presbyopia.
To give you monovision, your eye doctor will modify your contact lens prescription so one eye remains mildly nearsighted. (If you are wearing contact lenses for farsightedness, your farsightedness can be intentionally overcorrected in one eye make that eye mildly nearsighted.)
When monovision is successful, one eye sees distant objects clearly, and the other (mildly nearsighted) eye sees near objects clearly. With both eyes open, vision is clear and comfortable at all distances.
Though the concept of monovision may sound odd, the success rate is very high. Approximately 75 percent of people who try monovision are pleased with it. Still, it has some limitations. Ask your eye doctor for a trial fitting to determine if monovision is right for you.
Even if you currently don't need corrective lenses for distance vision, you still may be a good candidate for monovision. This would require wearing a disposable soft contact lens in just one eye. Though you may not see as clearly up close as you would with reading glasses, monovision would give you the convenience of not having to carry reading glasses with you wherever you go. See your eye doctor for a trial fitting to determine if this would work for you.
Bifocal contact lenses are another option for the correction of presbyopia. The success rate for bifocal contact lenses is comparable to monovision. However, these lenses are more expensive than lenses used for monovision.
In some cases, your eye doctor may determine that you will have the best results with a bifocal contact lens on one eye and a standard contact lens on the other. This technique is called modified monovision.
Refractive surgery can also be used to correct presbyopia. Though it cannot restore distance vision and near vision in the same eye, LASIK and other types of refractive surgery can correct presbyopia with the same monovision technique used with contact lenses.
If you already wear contact lenses, most eye doctors recommend that you try monovision with contact lenses for a period of time to determine if this is a good option for you before you have monovision refractive surgery performed.
The success rate with monovision refractive surgery is comparable to the success rate with monovision contact lenses.
Refractive surgery results are permanent. But if you have monovision with LASIK refractive surgery and are dissatisfied with your vision, your surgeon can usually perform a second LASIK procedure on the near eye to restore distance vision in that eye (eliminating the monovision).
Ask your eye doctor to refer you to a refractive surgeon if you are interested in LASIK or other refractive surgery as a possible treatment option for nearsightedness, farsightedness, astigmatism or presbyopia.