If you've reached your mid-40s or beyond, you're likely to experience difficulty focusing on tasks at a close distance such as reading fine print. More likely than not, you need "reading" glasses. The problem is particularly exasperating if you already use glasses or contact lenses to correct your distance vision. If you don't want to wear bifocal spectacles or reading glasses on top of your contact lenses or to have separate prescriptions for distance and near vision, multifocal contact lenses offer an attractive alternative.
Multifocal contact lenses correct both distance and near vision by including two or more prescriptions in one lens. Most multifocal contact lenses are available as ordinary soft contacts lenses or as rigid gas permeable (GP) contact lenses that allow oxygen to pass through them, much as silicone hydrogel soft lenses do. There are two types of multifocal contact lenses: translating and simultaneous vision.
Translating contact lenses. These contact lenses resemble bifocal glasses, with a line separating the distance prescription on top from the near-vision prescription below. A third prescription for intermediate distance (for instance, the working distance from a computer) also can be added, making them similar to trifocal spectacles.
The advantage of translating contact lenses is that they stay in place when you blink because they are weighted at the bottom. To use the near-correction prescription, you simply lower your gaze. The drawback is that because they're made of a more rigid material than traditional soft lenses, they may not be comfortable initially.
Simultaneous contact vision lenses. These contact lenses enable you to look through the distance and near powers of the contact lenses simultaneously. The lenses may be concentric or aspheric in design.
- Concentric lenses. Contact lenses with this pattern have one vision prescription in a ring at the center, which is surrounded by larger rings that alternate between the near and distance prescriptions. An additional ring can be added to improve vision at intermediate distances.
- Aspheric lenses. With these contacts lenses, both the near and distance prescriptions are placed on or close to your pupil. When you look at something that is far away, your eyes learn to ignore objects that are close by. Conversely, when you focus on an object that is close, your eyes learn to ignore things that are far away. The challenge is to learn to pick the part of the lens you need from moment to moment.
What's best? The best type of contact lenses for you depends on the size of your pupils and the strength of your near-vision prescription. You may have to try several kinds to find the one that's most comfortable.
