As baby boomers reach middle age, the question looms large: How to avoid either of two telltale signs of aging -- bifocals or reading glasses?

Boomers have three contact lens options for correcting the close-up blurred vision that typically begins in middle age; a condition referred to as presbyopia. (One of the three options still calls for reading glasses, but they can be used discreetly.)

The three options are:

• Bifocal contact lenses
• Monovision
• Contact lenses for distance vision with supplementary reading glasses slipped over the contacts for close work

Bifocal contact lenses
One of the two main categories of bifocal contact lenses may be suitable for you:

Simultaneous vision
With simultaneous vision bifocals, you look through both the reading and distance portions of the lenses all the time. This means that whenever you look at an object, you see two images of it. One will be clear (from the portion of the lens most matched to the distance at which you are observing). The other will be blurred (from the other portion of the lens). Your brain learns to ignore the blurred image so that you see the other clear image.

Translating
Translating bifocals are similar in concept to bifocal eyeglass lenses. They have a thicker lower edge, which, when you look down to read, rests on the lower lid. As your eye turns downward to read, it looks through the reading portion in the lower part of the lens. In fact, even though they "translate," a portion of vision through this type of bifocal is of the simultaneous type.

If you wear bifocal contact lenses, they will normally perform optimally in bright conditions. Because bifocal lenses divide the light into two images, each of which will use about half of the available light, you may find that, in dimly lit conditions, seeing is more difficult with bifocal contacts. Driving at night may present more difficulty, for example.

Monovision
Monovision is an option in which one eye is fitted with a lens for seeing things at a distance and the other eye is fitted for seeing close-up. After a period of adjustment, the brain switches to the eye that is giving the clearest image at the time.

While many people successfully use monovision, others find adapting difficult. Mildly blurred vision, dizziness, headaches and a feeling of slight imbalance may last for a few minutes or for several weeks as you adapt. Generally, the longer these symptoms last, the more unlikely it is that you will adapt successfully. Approximately two-thirds of patients eventually adapt to a monovision correction.

Adjusting to demanding conditions
If you are new to monovision you may benefit from avoiding visually demanding situations at first, and instead to wear their new lenses only in familiar situations. For example, it may be better to be a passenger, rather than a driver, in a car. In fact, you should only drive with monovision correction if you can pass your driver's license eye examination while wearing it.

Coping in special situations
Some people are uncomfortable in situations with low illumination, such as night driving. If that is your concern, ask us about prescribing an additional lens to correct both eyes for distance for those times when sharp distance vision is required. An alternative is a pair of glasses with additional power in the reading eye so that the combined power of your contacts and the spectacles match your distance prescription.

If you require very sharp near vision, you might want to ask about an additional lens to correct both eyes for close-up work. Or, to occasionally have the clearest vision for critical tasks, you may want to request supplemental glasses to wear over your monovision correction, converting the distance eye to a reading prescription so that you can use both eyes at near distance.

Contacts for distance; reading glasses for near vision
The final option for correcting presbyopia is this: Wear contact lenses for distance, then slip some reading glasses over them for close-up work. Perhaps not the perfect answer, this option enables you to avoid the dreaded bifocal glasses. And that can still be a definite plus.