Purchasing a pair of eyeglasses can be an intimidating experience for many people, even though over 50% of all Americans use some type of prescription eye wear. Patients typically only buy glasses every few years, so it's difficult to stay abreast of changes in technology, styles, brands, and pricing. The goal of this section is to educate patients on eyeglasses and the buying experience so they will make the decisions best suited to them.
Single vision lenses are intended to correct for one of the two common types of refractive error─nearsightedness (myopia) or farsightedness (hyperopia)─ and may also correct for astigmatism. For example, patients with myopia have difficulty seeing objects in the distance, so the lens is made to improve distance vision.
Multifocal lenses correct for more than one refractive error. The most common multifocal lens is the BIFOCAL lens, where the upper portion of the lens is corrected for distance viewing and the lower portion of the lens is corrected for near viewing (14 – 20 inches). TRIFOCALS add a third segment, typically just above the near segment, to allow for intermediate viewing (20 -36 inches). With traditional bifocals and trifocals, the near and intermediate segments are distinct, so they are referred to as LINED BIFOCALS or LINED TRIFOCALS.
Progressive lenses were developed in 1958 to eliminate the lines on bifocals and trifocals that many patients find bothersome. Progressive lenses also allow both distance and near vision, but provide a gradual transition between the different segments. Because there are no lines, progressive lenses are often considered to be more attractive than the lined bifocals or trifocals.
Did you know emeralds and crystals were used by the affluent as vision aids as early as the Roman era? GLASS lenses were the most common lens material from 1,000 A.D. until the 1980's. Glass lenses continue to be available today, although they are heavier, thicker, less protective and less cosmetically appealing than other types of lenses.
Plastic Lenses: Plastic lenses were first introduced in 1962 and became more popular than glass lenses in the 1980's. Traditional plastic lenses are as thick as glass lenses, but they are much lighter. In 1983, the POLYCARBONATE lens became commercially available. Polycarbonate lenses were lighter, thinner and more scratch-resistant (when combined with scratch coating) and impact-resistant than glass or plastic lenses, but the optics in these lenses were still not as sharp as glass or plastic lenses. In the past twenty years, the optics quality of polycarbonate lenses has improved dramatically and, because they are the most impact-resistant lens available, they are recommended for all children as well as for safety glasses.
High-Index Plastic Lenses: Several years later, high-index plastic lenses were introduced with great fanfare, since they were light, provided excellent optics, good scratch protection, and eliminated the “Coke-bottle” look for patients with high prescriptions. While high-index lenses are more expensive than regular plastic lenses, high-index lenses are the best option for over half of all patients when considering the weight, thickness and cosmetic appearance of the lenses.
Photochromatic Lenses: Photochromatic lenses, which darkness when exposed to bright light and become transparent when in dim light, were first introduced by Corning in the 1960's. The most common photochromatic lens today is the Transition™ lens. The speed at which these lenses change color has improved dramatically in the past ten years, but their popularity is waning as sunglass clips become popular and more cost-effective additions to regular eyeglass frames. In additional, the photochromatic lenses require direct exposure to sunlight to change, so they are not as effective in a car with closed windows.
Polarized Lenses: Polarized lenses are available in non-prescription and prescription sunglasses as well as sunglass clips. Polarized lenses reduce the glare coming from objects you are viewing, such as a wet street, windshield, oncoming cars and snow. In particular, fishermen find that polarized lenses provide significant vision improvement in lakes and rivers on sunny days. As in-office took can quickly demonstrate the usefulness of polarized lenses.
Once you select a lens material, you can also select whether to add the following options to your lenses.
Scratch-Resistant Coating can be applied to plastic lenses, they generally are standard feature on progressive, high-index, photochromatic and polycarbonate lenses. The coating provides a harder finish to the lens, making the lens more scratch resistant. Depending on the optical store, patients who purchase this coating may receive a no-cost twelve-month scratch warranty, where each lens will be replaced once if it becomes scratched in the year following the lens purchase.
Anti-reflective coating is a multi-layered coating that helps reduce lens surface reflection and improves vision by allowing more light to pass through the lens. Without anti-reflective coating, eyeglass lenses have a tendency to produce glare, reflections and halos around lights. Anti-reflective coating reduces these distortions and the lens reflections that other people see on your glasses when they look at you. Early versions of anti-reflective coatings wore off easily, but current coatings such as Crizal eliminated these problems. We offer 2 types of Crizal: the Avance for superior glare, scratch and smudge protection and the Prevencia with the same benefits as Avance with the added protection from blue-violet light that is emitted from computers, tablets, cell phones, LED and CFL lighting. A two-year no-cost warranty is also available for this premium anti-reflective coating.
Ultraviolet Coating is an additional lens application that blocks ultraviolet A (UVA) and ultraviolet B(UVB) emissions from the sun. Research suggests that UVA and UVB may cause early cataract formation, macular degeneration and eyelid damage.
Tinted lenses are an option for patients who are particularly sensitive to bright lights and sunlight. While tinting is an affordable option, it often reduces a patient's vision in dimly lit environments. Many patients now find more success with photochromatic lenses, prescription sunglasses or regular glasses fitted with a removable sunglass clip.
Selecting the right eyeglasses frame for you can be exciting, particularly if you want a new “look.” Your optician can help you find the frame material, size, shape and color that best suits you, although many patients rely on a family member or friend for final approval. Just like in the clothes industry, there are a wide variety of eyeglass frame styles, and cyclical trends may dictate what is “hip” now. For example, large eyeglasses were quite common in the 1970's, and after two decades of ‘smaller is better,” it is now fashionable to again wear oversized sunglasses. The list below includes some of the features that you should consider when selecting a frame:
Size: While smaller frames are still the norm for prescription eyeglasses, bifocals and progressive lenses do require a minimum frame size n order for the lens to function properly. Larger frames provide a wider field of vision for distance viewing, but dramatically increase the weight and edge thickness of the lenses.
Shape: Eyeglass frame are quite varies, so lens shapes may be round, oval rectangular or nay combination of shapes. The popularity of lens shapes is subject to the fashion trends, and the shape of a person's head may lend itself to a few specific lens shapes.
Material: Frames can be constructed from plastic, stainless steel, titanium, metal alloy, and other derivatives of plastic and metals. Each material varies in terms of weight, flexibility, durability and cost. In addition, rimless frames are also widely available and minimize the cosmetic presence of eyeglasses.
Hinges: In addition to the traditional hinges on eyeglass frames, many frames have spring hinges that bend in both directions. This feature is particularly important for children and active adults who are more likely to have their glasses hit by balls, toys and other people. Without the spring hinges, the force of a blow may damage the frames; with spring hinges, the glasses are more likely to flex with the impact and then return to the original shape. Finally, due to flexible materials like titanium, some frames may have no hinges, eliminating the opportunity for lost screws and enhancing the durability of the frame.
Nosepieces: Virtually all metal and metal alloy frames rest on the nose using “floating” nose pads, while plastic frames often rest directly on the nose. When nose pads are used, a smaller area of the eyeglasses is in contact with the nose, which may increase comfort. In addition, nose pads are adjustable for those of us with noses that are narrow, broad or slightly askew. Before purchasing a frame without nose pads, be sure the frame properly rests on your nose.
While less commonly sold than general-purpose eyeglasses, the following types of specialty eyeglasses are available:
Computer: Computer glasses generally have single-vision lenses corrected to crisply see objects 18 – 30 inches away. Because the lenses are corrected for only one distance, the patient can view the entire computer screen from all areas of the lens, reducing distortions, eye fatigue and neck pain.
Reading: Reading glasses are similar to computer glasses but are corrected to see objects 14- 16 inches away. These glasses are ideal for reading books and newspapers or for hobbies that require fine near vision. Less expensive over-the-counter reading glasses can be used for this purpose if a patient has limited astigmatism and needs the same correction power in both eyes.
Sports: Sports glasses and goggles are fom-fitting eyepieces with sturdy frames and polycarbonate lenses that can safely withstand the impact of collisions, racquetballs and other traumatic events.
Hunting: Hunting glasses are made with sturdy frames and polycarbonate lenses that can withstand the rigors of hunting and provide needed eye protection. In addition, the lenses are often corrected to specifically enhance distance vision and a yellow tint may be utilized to increase vision in dimly-lit environments.
Opticians have many key responsibilities. They assist patients in selecting the correct style and material for the frame and lenses, as well as the lens options that will be useful. They take key measurements to prepare for the manufacturing of the lenses, and they work with the laboratory to ensure the lenses are made correctly. Most patients find their eyeglasses need adjustments after a few months of wearing. Eye glass frame adjustments are complimentary, as routine maintenance is key to optimum vision through spectacle prescription glasses.