Refractive index is a measure of how well a material bends light. It varies with its speed of travel; the slower the light travels through a material, the greater the bending. The higher the index, the more efficient the material is at refracting light.
A high index lens bends light rays more, which allows it to be used in strong prescriptions. This type of lens is typically thicker in the center and is less likely to cause peripheral distortion. A high-index lens also fits into most frames and is often treated with anti-reflective coating to maintain optimum clarity.
UV++ lenses for eye glasses offer 100 percent UV protection and are available in a wide range of materials. Some are more durable than others and have excellent optical clarity. Other types of UV protection eyeglass lenses include polarized lenses and high-index plastic lenses.
Another option is to purchase blue-light-filtering lenses. Many electronic devices emit blue light which damages the retina and affects your sleep. Wearing sunglasses with these lenses will reduce the risk of blue-light damage and increase your production of melatonin during the night.
A pair of sunglasses with UV-protecting lenses will provide even better protection. Prescription eyeglass lenses with UV protection are just as effective as sunglasses and can protect your eyes from the sun’s UV rays. The American Academy of Ophthalmology recommends UV protection lenses for your eyeglasses.
If you can’t afford to purchase a UV-protecting lens, you can opt for clear lenses that are still protected by UV rays.
Polycarbonate lenses, for instance, block out nearly 100 percent of UV rays without the need for additional UV coating.
A scratch-resistant coating is an added layer of protection for your eye glasses lens. It is applied on non-scratch surfaces and hardens against scratches, including large gouges.
Scratch-resistant coatings can be applied to most eyeglass lenses. These include Trivex, high-index, and polycarbonate lenses. However, you can also choose to buy glasses without scratch-resistant coating. If you purchase lenses without scratch-resistant coatings, be sure to check for a warranty.
Many glasses come with warranties. Some warranties cover the lens coatings while others do not. Be sure to ask your optometrist which one is right for you. In most cases, the coatings are designed to last the entire duration of your prescription, which is generally about 28 to 30 months.
The coating prevents scratches from building up and will extend the life of your lens. Lastly, make sure to clean your lenses with a specific cleaning solution recommended by your optician. However, if you notice that the coatings have already started to degrade after one year, you should return the glasses.