How a Lens is Made
What Types of Eyeglass Lenses Are Available?
As technology advances so, too, do eyeglass lenses. In the past, eyeglass lenses were made exclusively of glass. Today, most eyeglasses are made of high-tech plastics. These new lenses are lighter, do not break as easily as glass lenses, and can be treated with a filter to shield your eyes from damaging ultraviolet light.
The following modern eyeglass lenses are lighter, thinner, and more scratch-resistant than glass lenses or the older, common plastic lenses.
- Polycarbonate lenses. These eyeglass lenses are impact-resistant and are a good choice for people who regularly participate in sports, work in an environment in which their eyeglasses may be easily scratched or broken, and for children who may easily drop and scratch their eyeglasses. Polycarbonate lenses also provide ultraviolet protection.
- Trivex lenses. These lenses are made from a newer plastic with similar characteristics of polycarbonate lenses. They are lightweight, thin, and impact-resistant and may result in better vision correction than the polycarbonate lenses for some people.
- High index plastic lenses. Designed for people who require strong prescriptions, these eyeglass lenses are lighter and thinner than the standard, thick "coke bottle" lenses that may otherwise be needed.
- Aspheric lenses. These eyeglass lenses are unlike typical lenses, which are spherical in shape. Aspheric lenses are made up of differing degrees of curvature over its surface, which allows the lens to be thinner and flatter than other lenses. This also creates an eyeglass lens with a much larger usable portion than the standard lens.
- Photochromic lenses. Made from either glass or plastic, these eyeglasses change from clear to tinted when exposed to sunlight. This eliminates the need for prescription sunglasses. These eyeglass lenses may not darken in a car because the windshield could block the ultraviolet rays from the sun.
- Polarized sunglasses. Light reflected from water or a flat surface can cause unwanted glare. Polarized lenses reduce glare and are useful for sports and driving. These lenses may cause the liquid crystal displays on the dashboard of cars to appear invisible.
The type of vision problem that you have determines the shape of the eyeglass lens. For example, a lens that is concave, or curves inward, is used to correct nearsightedness, while a lens that is convex, or curves outward, is used to correct farsightedness. To correct astigmatism, which is caused by distortions in the shape of the cornea, a cylinder shaped lens is frequently used. Simply put, the eyeglass lens is a tool you use to focus light appropriately onto your retina.
What Are Multifocal Eyeglass Lenses?
People who have more than one vision problem often need eyeglasses with multifocal lenses. Multifocal lenses, such as bifocals and trifocals, are eyeglass lenses that contain two or more vision-correcting prescriptions. In years past, you could spot a multifocal lens by the line separating the two sections. But today, multifocal lenses, called progressive lenses, can be made to look seamless.
- Bifocals. Bifocals are the most common type of multifocal lens. The eyeglass lens is split into two sections; the upper part is for distance vision and the lower part for near vision. They are usually prescribed for people over age 40 whose focusing ability has declined due to presbyopia. Presbyopia is an age-related change that affects the natural lens in the eye.
- Trifocals. Trifocals are simply bifocals with a third section used for people who need help seeing objects that are within an arm's reach. This additional segment is above the bifocal portion of the lens and is used for viewing things in the intermediate zone; for example, looking at a computer screen.
If you have questions about which eyeglass lens is right for you, talk to your eye doctor. He or she can help you choose the lens that best fits your lifestyle and vision needs.
Eyeglass Lens Coatings
There are almost as many eyeglass lens coatings as there are types of lenses. They include:
- Anti-reflective coating. If glare becomes a problem, consider an anti-reflective coating applied to new eyeglasses. Anti-reflective coating will reduce reflections, decrease halos around light, and create a nicer cosmetic appearance.
- Scratch-resistant coating and ultraviolet coating. Most eyeglass lenses today have built-in scratch resistant coatings and ultraviolet protection.
- Tinted lenses. Sometimes a light or dark hint of color on the eyeglass lens can be beneficial to aid in vision. For example, a yellow tint may increase contrast and a gray tint may not alter color perception with sunglasses. A light tint can also hide the signs of aging around the eyes.
- Mirror coatings. If you are looking for a purely cosmetic lens that allows the eyes to be hidden from view, then this is the coating for you. Mirror coatings come in a variety of colors such as silver, gold, and blue.
How Should You Care for Your Eyeglasses?
- Always store eyeglasses in a clean, dry place away from potential damage.
- Clean your eyeglasses with water and a non-lint cloth, as necessary, to keep them spot-free and prevent distorted vision.
- See your doctor annually to check your eyeglass prescription.
While eyeglasses can correct some common vision problems, it is important to have routine eye exams to keep the eyes healthy.