Eyeglasses

Lens designs

• Single vision lenses have one power across the whole lens, for distance or for near.
• Bifocals have two areas: distance on top and reading below, with a visible line.
• Trifocals add a middle area for things at arm’s length, such as a computer.
• Progressive lenses change power gradually from distance to near, with no visible lines. They take some getting used to.
• Computer or office lenses are set for screen and desk distances.
• Reading glasses help with close-up work. Store-bought readers can work for some people, but they don’t correct astigmatism or a difference between your two eyes. They are not a substitute for an eye exam.

Lens materials

• Plastic lenses are light and the most common.
• Impact-resistant lenses, such as polycarbonate, are thinner and much harder to break. They are the best choice for children and for sports.
• High-index lenses are thinner and lighter for strong prescriptions.

Coatings and tints

• Anti-reflective coating cuts glare and reflections, which helps with night driving and screen use.
• Scratch-resistant coating helps lenses last longer.
• UV protection blocks ultraviolet light. Many lens materials include it.
• Light-reactive lenses darken outdoors and clear indoors. They may not darken much inside a car.
• Prescription sunglasses, including polarized lenses, reduce glare from water and roads.

Lenses that filter blue light are widely sold. There is no good evidence that they protect your eyes or prevent eye strain. Screen breaks and blinking fully help more.

Glasses start with an eye exam. Your eye doctor checks your prescription and the health of your eyes. A blurry-vision problem is sometimes a sign of an eye condition that glasses can’t fix, so an exam matters even if you only want new glasses.

Next, you choose frames and lenses. An optician measures the distance between your pupils and how the frames sit on your face, so the center of each lens lines up with your eyes. This matters even more for progressive lenses and strong prescriptions.

New glasses can feel strange for a few days. The floor may seem to tilt, or things may look a little bigger or smaller. This usually settles within a week or two. With progressive lenses, move your head to point your nose at what you want to see, and look down through the lower part to read. If your new glasses still don’t feel right after two weeks, or they give you headaches, go back. The prescription or the measurements may need a check.

For children, choose sturdy, flexible frames that fit well, with impact-resistant lenses. A strap can help active or very young children.

• Clean your lenses with lens cleaner, or a drop of mild dish soap and warm water. Dry them with a clean microfiber cloth.
• Don’t wipe lenses dry with paper towels, tissues or your shirt. These can scratch them.
• Take glasses off with both hands, so the frame doesn’t bend.
• Keep them in a hard case when you aren’t wearing them. Never leave them lens-down.
• Don’t leave them in a hot car. Heat can damage coatings and frames.
• Have your frames adjusted if they slide down or sit crooked.
• Keep an older pair as a backup.

Have your eyes checked as often as your eye doctor suggests. Your prescription can change, and an eye exam also looks for eye diseases that don’t cause symptoms early on.