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Presbyopia

Definition:
Presbyopia — the gradual loss of your eyes' ability to focus actively on nearby objects — is a not-so-subtle reminder that you've reached middle age. A natural, often annoying part of aging, presbyopia usually develops after age 40.

You'll likely become aware of presbyopia when you start needing to hold print at arm's length in order to read it. If you're nearsighted, you might temporarily manage the problem by reading without your glasses.

A basic eye exam can confirm presbyopia. You can correct the condition with nonprescription reading glasses or prescription eyeglasses or contact lenses. Surgery also may be an option.

Causes:
In order to "create" an image, your eye relies on two structures to focus the light reflected from objects: the cornea — the clear, dome-shaped front surface of your eye — and the lens — a clear structure about the size and shape of an M&M candy. Both of these structures bend (refract) light entering your eye to focus the image on the retina, located on the inside back wall of your eye.

The lens, unlike the cornea, is somewhat flexible and can

change shape with the help of a circular muscle that surrounds it. When you're looking at something far away, the circular muscle relaxes. When you're looking at something nearby, the muscle constricts, allowing the relatively elastic lens to curve more steeply and change its focusing power.

Most experts agree that presbyopia is caused by a hardening of your lens, which in turn develops with aging. As your lens becomes less flexible, it can no longer change shape, and close-up images appear out of focus.

When to seek medical advice :
If your problem with close-up vision is pronounced enough that you're no longer comfortable reading or doing close work, or if blurry close-up vision is keeping you from enjoying normal activities, see an eye doctor. He or she can determine whether you have presbyopia and advise you of your options.

Symptoms:
If you have presbyopia, you may :

  • Find that print appears unclear at a normal reading distance
  • Experience eyestrain or headaches from prolonged reading or close work

Diagnosis:
Presbyopia is diagnosed by a basic eye exam. This exam is generally administered by either an ophthalmologist or an optometrist. An ophthalmologist, who has a doctor of medicine (M.D.) degree, is a specialist trained to diagnose and manage eye disorders, including those that may require either medical or surgical treatment. An optometrist, who has a doctor of optometry (O.D.) degree, can perform many of the same services as an ophthalmologist, such as evaluating your vision, prescribing corrective lenses and diagnosing common eye disorders. In some states, optometrists also treat selected eye disorders with drugs. However, an optometrist may refer you to an ophthalmologist for more complex eye problems and for surgical procedures.

A complete eye examination involves a series of tests. Your eye doctor may use odd-looking instruments, aim bright lights directly at your eyes and request that you look through an array of lenses. Each test is necessary and allows your doctor to evaluate a different aspect of your vision.

According to the American Academy of Ophthalmology, if you don't wear glasses or contacts, have no symptoms of eye trouble and are at a low risk of developing eye disease, you should have your eyes examined at the following intervals :

  • Every five to 10 years under age 40
  • Every two to four years between ages 40 and 64
  • Every one to two years beginning at age 65

However, if you wear glasses or contacts, have your eyes checked more often. And if you notice any problems with your vision, schedule an appointment with your eye doctor as soon as possible, even if you've recently had an eye exam. Blurred vision may suggest you need a prescription change or have another eye problem that may need evaluation and treatment.

Treatment:
The goal of treatment is to compensate for the inability of your eyes to focus on nearby objects. Treatment options include wearing corrective lenses, undergoing refractive surgery or getting lens implants.

Corrective lenses
If you had good, uncorrected vision before developing presbyopia, you may be able to use nonprescription reading glasses. But check with your eye doctor about what's right for you.

Reading glasses sold over-the-counter are labeled on a scale that corresponds to the degree of magnification (power). The least powerful are labeled +1.00, and the most powerful +3.00. When purchasing reading glasses, try out a few different powers until you find the magnification that allows you to read comfortably. Test each pair on printed material held about 14 to 16 inches in front of your face.

You'll need prescription lenses for presbyopia if over-the-counter glasses are inadequate or if you already wear corrective lenses for nearsightedness, farsightedness or astigmatism. Your choices include :

  • Prescription reading glasses. If you have no other vision problems, you can have prescription lenses for reading only.
  • Bifocals. These glasses come in two styles — those with a visible horizontal line and those without a line (progressive bifocals). When you look through progressive bifocals at eye level, the lenses correct your distance vision. This correction gradually changes to reading correction at the bottom.
  • Trifocals. These glasses have corrections for close work, middle-distance vision — such as for computer screens — and distance vision. Trifocals can have visible lines or progressive lenses.
  • Bifocal contacts. Bifocal contact lenses, like bifocal glasses, provide distance and close-up correction on each contact. The bottom, reading portion of the lens is weighted to keep the lens correctly positioned on your eye. These are frequently difficult to fit and often do not provide altogether satisfactory visual results.
  • Monovision contacts. With monovision contacts, you wear a contact lens for distance vision in your dominant eye and a contact lens for close-up vision in your nondominant eye. Your dominant eye is generally the one you use when you're aiming a camera to take a picture.
  • Modified monovision. With this option, you wear a bifocal contact lens in your nondominant eye and a contact lens set for distance in your dominant eye. You use both eyes for distance and one eye for reading. Your brain learns which lens to favor — depending on whether you're viewing things close up or far away — so you don't have to consciously make the choice of which eye to use.

Refractive surgery
Refractive surgery changes the shape of your cornea. For presbyopia, this treatment — equivalent to wearing monovision contact lenses — may be used to improve close-up vision in the nondominant eye. The American Academy of Ophthalmology recommends that people try monovision contacts to determine if they can adjust to this kind of correction before considering refractive surgery.

Most refractive surgical procedures were developed to correct nearsightedness, farsightedness and astigmatism. Few studies have been published about the long-term effectiveness of monovision refractive surgery for people with presbyopia, but some evidence suggests that the surgery may help some people with presbyopia reduce their dependence on corrective lenses. Eventually, though, many people who have had refractive surgery will still need corrective lenses for reading.

Refractive surgical procedures include the following :

  • Conductive keratoplasty (CK). This procedure uses radio frequency energy to apply heat to very tiny spots around the cornea. The degree of change in the cornea's curvature depends on the number and spacing of the spots, as well as the way in which the corneal tissue heals after the treatment. The results of CK are variable and unstable in many people.
  • Laser-assisted in-situ keratomileusis (LASIK). With this procedure, your eye surgeon uses a laser or an instrument called a keratome to make a thin, hinged flap in your cornea. Your surgeon then uses an excimer laser to remove inner layers of your cornea to steepen its domed shape. An excimer laser differs from other lasers in that it doesn't produce heat.
  • Laser epithelial keratomileusis (LASEK). Instead of creating a flap in the cornea, the surgeon creates a flap only in the cornea's thin protective cover (epithelium). Your surgeon will use an excimer laser to reshape the cornea's outer layers and steepen its curvature and then reposition the epithelial flap.
  • Photorefractive keratectomy (PRK). This procedure is similar to LASEK, except the surgeon removes the epithelium. It will grow back naturally, conforming to your cornea's new shape.

Lens implants
Another procedure used by some ophthalmologists involves removal of your clear natural lens and replacement with a synthetic lens inside your eye (intraocular lens implant). The synthetic lens implant is designed to allow your eye to see things both near and at a distance. However, synthetic lens implants haven't been entirely satisfactory; recipients have experienced problems with glare and blurring. In addition, this surgery carries with it the same risks associated with cataract surgery, such as inflammation, infection, bleeding and glaucoma.

 
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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