At EyeBuyDirect, all standard lenses are made of lightweight CR39-resin with a standard lens index of 1.499, coming with a completely scratch resistant coating. Polycarbonate lenses are the lightest material available (optional) and due to its high impact-resistance and durability, it also happens to be an integral material used in making bullet-proof "glass".
Single vision lenses
Single vision lenses have one fixed focus point or correction over the entire lens area. They can be used for either near, intermediate or distance vision. For instance, glasses for driving or reading are single vision. EyeBuyDirect's standard free lens is single vision.
A bifocal lens is divided into two sections by a horizontal line with the upper section of the lens usually used for distance vision and the lower section used for near vision. These two different focuses in the one lens allow people with myopic or hyperopic conditions to use a single pair of glasses for both long distance and up-close vision.
Also known as varifocals, progressive lens type serves the same purpose as bifocals but without the obvious horizontal line segmenting the lenses. It provides a smooth transition between distance and near vision, as well as the capability for viewing intermediate ranges.
Our premium anti-glare coating is ideal for computer use and night driving. They work by increasing the light transmission through the lenses providing you with the clearest, sharpest vision at all times. Any great-looking pair of eyeglasses will look even better: people will see your eyes through the lenses, not the light reflection!
No eyeglass lens material - not even glass - is scratch-proof. However, a lens that is treated front and back with a clear hard coating does become more resistant to scratching whether it's from dropping your glasses on the floor or occasionally cleaning them with a paper towel. All our glasses get an anti-scratch coating.
Premium water repellant coating
These premium water repellent coatings prevent water drops for sticking to the surface and spreading. It is also used to resist fingerprint and dirt accumulation, providing easier-to-clean surfaces which stay cleaner for approximately twice as long.
These premium water repellent coatings also prevent water drops for sticking to the surface and spreading. Instead, they stay contained and simply slide off the lens surface, "built-in windshield wipers," in effect.
This superior water repellency also provides oleophobic resistance as well, since it's been well established that oil and water don't mix! These premium quality lens attributes are possible because they are chemically bonded with the top portion of the lens material, and are not just an applied surface finish.
As consumers, our interest in thin and light extends to more than just potato chips and beer - it has impacted eyeglasses in a very significant way. Most eyeglass wearers are nearsighted and a basic physical property of nearsighted lenses is that their edges are thicker than their centers. The stronger the prescription, the thicker the edges (see lens drawings below). Most of today's fashionable frames are made of plastic or metal with rims thinner than the lens itself. Also very popular are rimless mountings where the lens edges are completely exposed. In either case, the lens edges are highly visible and thicker edges can detract from the appearance of the eyewear. We provide two kind of thinner lenses: 1.57 called thin and lite, 1.6 called super thin.
Another lens treatment that is beneficial but invisible to the naked eye is ultraviolet (UV) protection. Just as we use sunscreen to keep the sun's UV rays from harming our skin, UV treatment in eyeglass lenses blocks those same rays from damaging our eyes. Overexposure to ultraviolet light is thought to be a case of cataracts, retinal damage and other eye problems. An ultraviolet treatment is simple and quick to apply to most plastic eyeglass lenses and it does not change the appearance of the lenses at all.
As opposed to the changeable photochromics, another option in colored lenses is a tint which remains constant at all times. Tints are available on our glasses with the following colors: brown, grey and green (available 20%, 40%, 60%, 80%). Lighter, fashion tints are used primarily for cosmetic purposes to enhance a wearer's looks. Darker tints allow the wearer to use the lenses as sunglasses.
A gradient lens refers to the distribution of the color tint in the lens and the cosmetic effect created with a darker upper lens (80%) and a clearer lower lens (10%). It only can be applied to the frame with height of 36mm and above.
A gradient lens provides both a cosmetic and utilitarian function. They are a fashion feature unto themselves, defining a lens which is darkest at the top, gradually lessening in color saturation toward the bottom of the lens.
Functionally, they allow you to effectively wear sunglasses on a slightly cloudy day, or toward dusk. When your eyes are raised or looking more toward the sun or light source, you have the protection of a regular pair of sunglasses. Yet, in an only moderately bright environment, or if you need to clearly see something that is closer to you, the bottom of the lens is without tint, in order to maximize the light available for viewing closer images more easily.
Free-form progressive lenses
A computer aided design and manufacturing process to minimize the potential uncomfortable effects of a progressive lens, reducing vertigo and imbalance, and improving the transition when shifting from one focal depth to another in a blended lens. The free-form lens process also widens the intermediate and near visual fields.
The free-form progressive lens describes an advance not unlike the effects applied to digital photography or high-definition television, a process by which higher pixel distribution provides greater resolution and clarity of image, and flatter, more cosmetically attractive lens. There is a whole variety of branded names, all basically seeking to describe digitized lens technology driven by computer programs utilized by lens casters and finishers to overcome optical aberrations and mechanical limitations of traditional surfacing. Traditional progressive lens compounded aberration problems because they used asymmetric curves, on the front of the lens, to correct for distance, intermediate and near vision, which create distortions on the lens surface.
These computer numeric controlled lens became the basis for free-form machines which now have power cutting tolerances of less than 1/100th of a diopter and finishers for polishing to 1 micron. The lens utilized by EyeBuyDirect also provide the advantage of moving the correction to the back of the lens surface (along with the power corrections), closer to the eye, which location serves to vastly improve image quality, reduce vertigo-producing distortion, and widen the field of view for mid-range and reading portions of the lens, particularly helpful for people with stronger visual corrections!
Photochromic lenses (Light-adjusting lenses)
Photochromic lenses provide the correct amount of protection for the varying light conditions you experience.
Photochromic lens darken when being exposed to UV (ultraviolet) rays. Once the UV rays are absent (for example, walking indoors), the lens will gradually return to their clear state.
Thanks to photochromic lenses, eyeglass wearers can purchase one set of glasses that will allow them to see inside, as well as provide sun protection outdoors.
Important facts are:
- Clear as an ordinary lens indoors and at night
- Block 100% of sun's harmful UVA & UVB rays
- Available in Gray or Brown
- Because photochromic compounds fade back to their clear state by a thermal process, the higher the temperature and altitude, the less dark photochromic lenses will be. This thermal effect is called "temperature dependency" and prevents these devices from achieving standard sunglass darkness in very hot weather and at sea level. Conversely, photochromic lenses will get very dark in cold weather conditions and at higher altitudes, which make them more suitable for snow skiers than for optimum performance at the beach. Because vehicle windshields contain UV protection, this retards the performance of the metallic oxide compound coating the photochromic lens. If you prefer a dark lens for driving, we recommend an 80% tint be applied, which, while not as convenient as having one multi-functional pair of glasses, will give you more lens coloration inside the vehicle.
A finish provided to eyeglass lens which reduces the amount of glare reflected from surfaces such as water, metal or highway road finishes.
When electromagnetic waves (i.e., light) are reflected from a surface, the waves are strongest in one direction, usually horizontally in the case of water, metal or other flat surfaces and this reflected light can be both annoying and dangerous, as it strikes the viewers eyes intensely, creating glare. Polarization is a property of free traveling light waves that describes the orientation of their oscillations, which are perpendicular to the direction the light wave is traveling.
In creating a polarized optical lens, tiny transparent strips are laminated to vertically angle light, and can block approximately 50% of the light from passing through the lens. Think of a mini-blind, and how it changes the angle of light entering a room because it prevents direct entry of sunlight, yet there is plenty of ambient light to see well, even though you aren't getting direct rays. Polarized sunglasses typically have a thin film on one side of the lens, or the film may be laminated between lens layers. The more dense the film, the more polarization it provides, and the more costly it becomes.
A note – polarized lens tend to block LCD displays (cell phones, dashboards and GPS), and may block the reflected light from ice patches on snow, when downhill skiing.