Presbyopia

During middle age, usually beginning in the 40s, people experience blurred vision at near points, such as when reading, sewing or working at the computer. There's no getting around it — this happens to everyone at some point in life, even those who have never had a vision problem before.

Currently an estimated 90 million people in the United States either have presbyopia or will develop it by 2014. This is generating a huge demand for eyewear, contact lenses, and surgery that can help presbyopes deal with their failing near vision.

When people develop presbyopia, they find they need to hold books, magazines, newspapers, menus and other reading materials at arm's length in order to focus properly. When they perform near work, such as embroidery or handwriting, they may have headaches or eyestrain or feel fatigued.

Presbyopia is caused by an age-related process. This is different from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and caused by genetic factors, disease or trauma. Presbyopia is generally believed to stem from a gradual loss of flexibility in the natural lens inside your eye.

The eye's lens stiffens with age, so it is less able to focus when you view something up close. The result is blurred near vision. (Illustration: Varilux)

These age-related changes occur within the proteins in the lens, making the lens harder and less elastic with the years. Age-related changes also take place in the muscle fibers surrounding the lens. With less elasticity, the eye has a harder time focusing up close. Other, less popular theories exist as well.

Eyeglasses with bifocal or progressive addition lenses (PALs) are the most common correction for presbyopia. Bifocal means two points of focus: the main part of the spectacle lens contains a prescription for nearsightedness or farsightedness, while the lower portion of the lens holds the stronger near prescription for close work.

Progressive addition lenses are similar to bifocal lenses, but they offer a more gradual visual transition between the two prescriptions, with no visible lines between them.

Reading glasses are another choice. Unlike bifocals and PALs, which most people wear all day, reading glasses are typically worn just during close work. If you wear contact lenses, your eye doctor can prescribe reading glasses that you wear while your contacts are in. You may purchase readers over-the-counter at a retail store, or you can get higher-quality versions prescribed by your eyecare practitioner.

There are contact lenses for presbyopes, called multifocal contact lenses. You can obtain multifocal contact lenses in gas permeable or soft lens materials. Another type of contact lens correction for presbyopia is monovision, in which one eye wears a distance prescription, and the other wears a prescription for near vision. The brain learns to favor one eye or the other for different tasks. But while some people are delighted with this solution, others complain of dizziness or nausea or miss the depth perception they once had.

Because the human lens continues to change as you grow older, your presbyopic prescription will increase over time as well. You can expect your eyecare practitioner to prescribe a stronger correction for near work as you need it.

New surgical options to treat presbyopia are being researched and are already available in many countries. One example is Refractec Inc.'s conductive keratoplasty, or NearVision CK treatment, which uses radio waves to create more curvature in the cornea for a higher "plus" prescription to improve near vision. The method was FDA-approved for the temporary reduction of presbyopia in April 2004. (In 2002 it had been approved for mild farsightedness.) Read more about how CK works.

A highly experimental treatment is a soft, elastic polymer gel that researchers say would be injected into the capsular bag, the cavity that contains the natural lens. In theory, the gel would replace the natural lens and serve as a new, more elastic lens. Experiments also have centered on laser treatment of the eye's hardened lens to increase flexibility and improve focus.

With the recent introduction of presbyopia-correcting intraocular lenses, some people undergoing cataract surgery may be able to achieve clear vision at all distances. Also, an elective procedure known as refractive lens exchange may enable you to replace your eye's natural lens with an artificial one using presbyopia-correcting lenses.
 

Other methods are being researched as well. Read more about surgical options for presbyopia.