Eyeglasses: Choosing Lenses

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KEY POINTS

• When you get new glasses, you and your eye care provider need to decide if you need single vision or multifocal lenses that correct more than one vision problem; whether to get glass or plastic lenses; and if you need coatings to prevent reflection, scratches, or glare.

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When you get new glasses, there are three important things you need to know about lenses:

• The kind of lenses (single vision or multifocal lenses that correct more than one vision problem)
• The lens material (glass or plastics)
• Coatings applied to the lenses (such as coatings to prevent reflection, scratches, or glare)

What lens design is right for me?

Your eye care provider will advise you about different types of lenses. You may need either single-vision lenses or multifocal lenses.

Single-vision lenses correct a single vision problem, such as farsightedness, which is when you see distant objects clearly, but close objects are blurry.

Multifocal lenses correct more than one vision problem (such as reading vision and distant vision). There are different types of multifocal lenses, for example:

• Bifocals: Lenses for these glasses are divided into two sections. You can see the line that divides the top and bottom parts. Usually the top part is for distance vision and the bottom part is for close vision. Some glasses can have the close-up vision in a different shape and place. For example, electricians who look up to do close work with wires may have the close-up vision at the top of the lens.
• Trifocals: These are just like bifocals, except the lens is divided into 3 sections. The top is for distance, the middle for arm’s length vision, and the bottom for close-up vision. You can see the lines that divide the sections. The mid-range of trifocals is helpful if you spend a lot of time using computers.
• Progressive lenses: Progressive lenses have no line in the lens dividing the sections. Instead, there is a smooth transition between the sections of the bifocals or trifocals. There is some distortion on the outer edges of the lenses. You get the best vision when you point your nose directly at what you want to see. It takes some time to adjust to wearing progressive lenses.

Children rarely need multifocal lenses. If your child needs multifocal lenses, your eye care provider will advise you which kind to get.

What materials are used for lenses?

Glass lenses

• Regular: Glass lenses are not as easy to scratch as plastic lenses. They also can be used for many types of prescriptions. However, they are heavier than plastic lenses, and may break more easily with impact.
• High-index or aspheric: Glass lenses can also be made from a special type of glass called high-index. This type of glass is compressed so that lenses are much thinner and lighter than normal lenses. High-index glasses can be helpful if you have a strong correction and would usually need very thick glasses. Aspheric lenses use the high-index material as well as special design techniques to make the lenses thinner. High-index lenses have built-in protection against ultraviolet (UV) rays.

Plastic Lenses

• Hard resin: Hard resin lenses are half the weight of glass. Hard resin lenses are more easily scratched than glass, but they are durable.
• High-index or aspheric: High-index plastic lenses work the same way as high-index glass lenses. These lenses are made from a compressed material, and can be made with special design techniques to make the lenses thinner. These lenses have built-in protection against ultraviolet (UV) rays.
• Polycarbonate: This is a shatter-resistant material. It is best for kids, athletes, or people who need safety glasses for work. Polycarbonate lenses are another type of high-index lens and are light and comfortable. They also have built-in UV protection. For the best protection, you should also get special frames that are impact resistant.

What coatings or treatments are available for lenses?

• Antireflective coating: This coating reduces glare. However, you need to take extra care of your glasses to keep the coating from wearing away. When the coating wears off, the glasses may not work as well.
• Scratch-resistant coating: This coating is very helpful for plastic lenses, which are more likely to scratch than glass.
• UV coating: This coating helps protect your eyes from the sun's harmful ultraviolet rays. You can get a UV coating on both tinted and clear lenses. Polycarbonate and high-index lenses already have UV protection.
• Mirror coating: These coatings come in several colors and prevent people from seeing your eyes. This coating helps protect the eyes against glare from surfaces such as water or snow.
• Polarized lenses: This treatment is good for outdoor wear. It helps cut down on glare and gives better clarity and depth perception.
• Tinted lenses: Most lenses can be tinted in a variety of colors. Tinted lenses may help increase contrast and reduce glare.
• Photochromatic or Transitions lenses: These lenses automatically darken when you go outdoors and return to normal when you go back indoors. They may be more comfortable for people who are sensitive to light.