Eyeglass lenses may all look the same, but aside from the prescription, they also have differences in make and characteristics. Choosing the right lens will affect how satisfied you will be with your eyewear.
Choosing the lens and coating may be a bit tricky due to so many available selections. Once you’ve completed your eye check, like a Sam’s Club eye exam, the optometrist may present you with different types of glasses to choose from. As the information can be too much to process in such a short time, better be prepared and learn the differences in the types of glasses.
Before, spectacles were made of glasses. Due to the instances of breakage, new lenses are now made with plastic. They are harder to break and are significantly lighter.
- CR-39 – The first of this lightweight material was developed by the California-based Armorlite Lens Company in 1947. They were made of Columbia Resin 39 plastic, which is still popular today because of the high-quality products they produce and the low production cost.
- High-Index – More than 20 years ago, the demand for lighter and thinner eyeglasses increased, and this led to the development of high-index plastic lenses. They are lighter than CR-39 and have a higher refractive index.
- Polycarbonate – This was first introduced by Gentex Corporation in the 1970s. They are very light and highly resistant to impact because they were originally developed as bullet-proof glasses for banks and the Air Force. This is the preferred glasses for sports, safety equipment, and children.
- Trivex – This product is made of the lightest possible plastic, has great resistance to impact, and is able to block 100% UV rays.
- Refractive Index – This determines the light’s speed ratio in a vacuum, that is divided by the light’s speed in the material used. In simple terms, the index of refraction of the eyeglass is the efficiency level of the material to bend or refract the light that goes through it. If the material has high refractive index, the light will move slower through it—meaning, the light is bended and your eyes get more protection. As an example, CR-39 plastic has an index of about 1.50, while a high-index plastic has 1.70 to 1.74.
- Abbe Value – This is the measure of how the lens can disperse the different light wavelengths that pass through it. Materials with low value have high levels of dispersion hat can cause colored halos surrounding objects and lights, which is called chromatic aberration.
- Aspheric Design – This design makes the lenses slimmer and more attractive. Manufacturers use flatter curves, which result in the curvature to gradually change from the center to the edge of the lens. This improves the person’s peripheral vision clarity; it does not magnify the person’s eyes; and has no negative impact on the general performance of the glasses.
- Edge Thickness – To correct nearsightedness, the center of the lens has the thinnest portion. To correct farsightedness, the edges of the lens have the thinnest portion. Trivex and polycarbonate are excellent for nearsightedness, while converging lenses correct farsightedness.
- Anti-scratch – Lightweight glasses are the most resistant to impact. However, they are also prone to abrasions and scratches because they are softer than glass. To improve their durability, manufacturers apply anti-scratch coating, especially to high-index plastic lenses, which makes them as resistant as glass.
- Anti-reflective – This coating reduces or eliminates light reflections, thus improving clarity and contrast, especially during night time. This also makes the glasses so clear that it will look as if the frame doesn’t have lenses at all. Beneficial if you’re having your photo taken, since glare spots are avoided. This coating is needed by high-index lenses, because they are highly reflective materials.
- UV-blocking – High-index and polycarbonate lenses have built-in UV protection system, while others like CR-39 will need added coating to get this feature. Protection from UV rays needs to be started from early childhood because accumulated radiation has been associated with muscular degeneration, cataract, and other eye problems that are related to aging.
- Photochromic treatment – This is a kind of treatment that allows lenses to automatically darken when exposed to UV and HEV (high-energy visible) rays of sunlight. When indoors, they quickly become clear again. This feature can be used in almost all designs and materials used.
The cost of your eyeglasses may depend on the features you want to be included in the lenses. Of course, the more advanced features, the more expensive it becomes. And then you have to consider the frame, since glasses should also make you feel nice about how they look on you. The doctor can advise which are the best lenses for your condition, and that’s what you should follow. You can also take advantage of the deals offered in optical shops so you could purchase your preferred glasses at a budget-friendly amount.