Presbyopia Ready For Reading Glasses - Other Common Eye Diseases Of Later Life: The Aging Eye Preventing And Treating Eye Disease

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Presbyopia: Ready for reading glasses?

One of the truest signs of aging is discovering that you need to hold menus and newspapers at arm's length in order to read them. Presbyopia — the Greek word for "old sight" — is a loss in the eye's focusing ability that may start as early as the late 30s, but typically develops in the 40s and 50s, eventually affecting everyone. It occurs when the aging lens becomes more rigid and less efficient in bending to accommodate changes in near and distant focus. An accompanying lag in the function of the ciliary eye muscles contributes to the difficulty in seeing small print.

Blurred close vision that leaves eyes tired and strained is an early hint of presbyopia's arrival. After reading or doing other detail work, you may find it hard to see distant objects clearly; the problem may be more pronounced after reading in poor light, or in the evening when you are tired. The condition occurs regardless of whether you are nearsighted, farsighted, or astigmatic; however, presbyopia often affects farsighted people at a younger age than those who are myopic (nearsighted). If you're nearsighted, you may be able to overcome presbyopia when it first develops simply by taking off your glasses to read. Eventually, however, as your presbyopia worsens and the lens of your eye becomes stiffer, you may need corrective lenses or other measures to cope with this common condition.

Corrective lenses. The most common remedy for presbyopia is optical correction — reading glasses. If you already wear corrective lenses, you might consider bifocals, trifocals, or progressive lenses, which combine several levels of adjustment to correct both distance and close-up vision problems. Some people use two pairs of glasses — one for distance and one for close work. Many drugstores and supermarkets carry magnifying reading glasses that may help. You should consult your ophthalmologist about an appropriate strength before purchasing a pair, and you should never buy reading glasses in lieu of having an eye examination. You can also get prescription contact lenses that correct the vision in one eye for reading and the other for distance — a technique called monovision. Newer multifocal contact lenses (combining several levels of adjustment, as found in reading glasses) are also available. Whichever type of lens you choose, you may need frequent changes in prescription, because presbyopia becomes progressively worse until about age 60–65, when it stabilizes.

Monovision. One option for people 40–60 years old with presbyopia but otherwise healthy eyes is monovision, in which one eye is corrected for close-up vision, leaving the other for distance vision. This approach doesn't fix the stiffened lenses that are the underlying cause of presbyopia, but it can eliminate the need for bifocals or multiple sets of glasses, and it may even enable you to read without glasses.

Doctors use various procedures to make the correction. Laser surgery techniques include LASIK, PRK, and LTK, each of which reshapes the cornea or the area around it to provide correction. (The technique used depends on your particular circumstances.) If you choose laser surgery and you never had focusing problems until presbyopia developed, the surgeon will correct one eye so you can see up close, leaving the other eye with your natural ability to see far. If you're both myopic and presbyopic, the doctor can correct your nondominant eye for near vision and your dominant eye for distance. It may take several surgeries to get the desired result, and the results may not be lasting.

Another technique used in monovision is conductive keratoplasty (CK). This method is similar to laser surgery but doesn't actually use a laser. Instead, CK uses short bursts of radio waves to shrink and reshape the cornea. One limitation is that it can take a few months before the full benefits are apparent. CK may also carry a slight risk of causing astigmatism.

Monovision isn't for everyone. It is vital that your eyes be healthy, even if you have presbyopia: No other eye defects, such as cataract, glaucoma, or corneal problems, can be present. Some people may find it too difficult to adjust to having different focusing abilities in each eye. If you're considering having this surgery, the FDA advises you to try monovision with contact lenses first, to find out whether you can adjust to having each eye focus differently.

Lens-replacement surgery. Improvements in the lenses used for cataract surgery have also provided another surgical option for people with presbyopia — albeit one that is an "off-label" use, meaning it's not FDA-approved, and one that is controversial. Variable-focus implantable lenses enable people who undergo cataract surgery to see objects at various distances (see "Accommodative and multifocal intraocular lenses"). Some ophthalmologists are now implanting these lenses in people without cataracts in order to correct presbyopia. This requires that your natural lenses be removed first, as is done in cataract surgery.

But keep two things in mind before undergoing this surgery for presbyopia. First, it will not be covered by insurance unless you have cataracts, and the cost can be $5,000 or more for each eye. Second, many ophthalmologists are reluctant to perform this procedure in people without cataracts because of the risks and lack of information about long-term safety and effectiveness. It's also important to understand that this surgery will not produce clear 20/20 vision.

Anterior ciliary sclerotomy (ACS). Another procedure that is not FDA-approved for presbyopia, but is sometimes performed, is anterior ciliary sclerotomy (ACS). In this procedure, the ophthalmologist makes a series of incisions in the sclera to provide more room for the lens to change shape with age. The theory behind this approach is not proven, and few studies have been published about safety or effectiveness.

Nearsighted? Farsighted? When the eye sees normally, light focuses directly on the retina, producing a clear image. But in some people, the optics are faulty, and images appear blurred because the eye focuses the image either in front of or behind the retina (see Figure 12). These problems are not eye diseases but common conditions known as refractive errors of the eye. Although laser surgery procedures such as LASIK and PRK have become increasingly popular as a way to correct refractive errors, such techniques are usually appropriate only for people younger than 50. For that reason, refractive errors in older adults are most often corrected with eyeglasses and contact lenses. Figure 12: Refractive errors Myopia (nearsightedness). A nearsighted person has difficulty seeing objects at a distance because the light rays converge and focus before reaching the retina. The cause is usually an elongated eyeball (which requires light rays to travel farther than they would in a normal eye) or a lens or cornea that is too strong, bending the light rays so they focus before getting to the retina. Hyperopia (farsightedness). People with this defect see objects better at a distance than up close. In this case, the eyeball is usually too short, and light rays reach the retina before they are focused. Hyperopia can also be caused by weaknesses in the refractive power of the lens and cornea. While farsightedness may go unnoticed for years, the eye's corrective ability diminishes with age, and a person will probably need glasses by midlife. Astigmatism. In this condition (not pictured), irregularities in the curvature of the cornea's surface cause distorted vision. Light rays do not meet at a single point, so images may focus at two different places. For some people, vertical lines appear blurry; for others, horizontal or diagonal lines may look out of focus. Astigmatism develops early and is usually well established after the first few years of life. The defect often occurs together with nearsightedness or farsightedness.

Last updated:	June 19, 2007