Selecting eyeglasses may seem to be just a matter of finding a fashion that the wearer likes, but anyone who walks into an optical store will soon discover that there is a dizzying array of lens choices available. Although the types of eyeglass lenses a person can choose is somewhat dictated by her prescription, even those with the most difficult of requirements have many options. Two of the key things for a shopper to consider are lens design and material.
When a person is buying lenses, the first order of business is to choose the lens design and brand. Those who wear single vision lenses will usually find the options to be fairly simple, and a store that has a laboratory on site can often have them made relatively quickly. Individuals with bifocal or multifocal prescriptions, however, have several options to choose from. The most inexpensive lens is a lined bifocal (or trifocal), which has strengths in it — a reading strength and distance strength. These strengths are separated by a line that can be seen pretty easily.
Once the most popular style of bifocal, the lined bifocal has taken a back seat to an advanced lens design, the progressive addition lens or PAL. Also called a “no-line bifocal,” this type has multiple strengths in one lens that change gradually as the user moves her eye down to the bottom of the lens. They have several advantages over lined bifocal, including the fact that they offer more than just a reading strength and distance strength. This allows users to see at arms-lengths and often eliminates the need for a lined trifocal. PALs also have a distinct aesthetic advantage over lined bifocals as they have no visible line.
The next choice is the selection of lens material. An optician will often make several recommendations based on the style of frame the buyer has chosen and her prescription. The advantages and disadvantages of the most common lens materials are summarized below.
|Plastic (CR-39)||Affordable, good optical clarity, easy to tint||Thick and heavy in high prescriptions|
|Polycarbonate||Thinnest material available, lightweight, best impact resistance, can be used in special frame designs, blocks UV light||Scratches easily, cannot be tinted dark, poorest optical quality|
|Hi-Index Plastic||Thinnest material available, lightweight, easy to tint||Expensive|
|Trivex||Impact resistant, thin, lightweight, excellent optics||Expensive, limited availability|
|Glass||Excellent optics, the most scratch resistant lens, blocks UV light||Heavy, thick, dangerous if broken, cannot be used in certain frame styles|
Once the style and material of lens has been chosen, several lens options may be added to your eyeglasses. These options, with both visual and aesthetic benefits, including the following:
- Photochromatic Lenses: Lenses that changes color when exposed to sunlight, often eliminating the need for separate sunglasses.
- Anti-Reflective Coating: Reduces glare, improving visual clarity and making the wearer's eyes easier to see. An excellent coating for nearly all types of lenses, especially for high prescriptions, as it makes lenses look less obvious.
- Scratch Resistance Coating: Extends the life of eyeglass lenses by providing a tough layer of protection. Scratch coatings often include a warranty.
- UV Coating: Important for individuals who spend a significant amount of time outside. Not necessary for polycarbonate or glass lenses, as these materials inherently block UV light.
- Tint: Added color for style or use as sunglasses.
- Polarized Lenses: A colored form of lens that reduces glare of off flat surfaces such as wet roads. The best choice for sunglasses.
There are so many different types of eyeglass lenses that, with a little information, it is easy for nearly everyone who wears glasses to get just the right thing to fit their prescription and lifestyle needs.