Photochromic lenses are optical lenses that darken on exposure to specific types of light of sufficient intensity, most commonly ultraviolet (UV) radiation. In the absence of activating light, the lenses return to their clear state.
Photochromic lenses may be made of glass, polycarbonate, or another plastic. They are principally used in eyeglasses that are dark in bright sunlight, but clear in low ambient light conditions. They darken significantly within about a minute of exposure to bright light, and take somewhat longer to clear. A range of clear and dark transmittances are available.
These processes are reversible; once the lens is removed from strong sources of UV rays, the photochromic compounds return to their transparent state. 

Anti-reflective coating (also called "AR coating" or "anti-glare coating") improves vision, reduces eye strain and makes your eyeglasses look more attractive.
These benefits are due to the ability of AR coating to virtually eliminate reflections from the front and back surfaces of your eyeglass lenses. With reflections gone, more light passes through your lenses to optimize visual acuity with fewer distractions (especially at night), and the lenses look nearly invisible — which enhances your appearance by drawing more attention to your eyes and helping you make better "eye contact" with others.
Today's modern anti-reflective coatings can virtually eliminate the reflection of light from eyeglass lenses, allowing 99.5 percent of available light to pass through the lenses and enter the eye for good vision.
Anti-reflective coating also is a good idea for sunglasses, because it eliminates glare from sunlight reflecting into your eyes from the back surface of tinted lenses when the sun is behind you. (Generally, AR coating is applied only to the back surface of sunglass lenses because there are no cosmetic or visual benefits to eliminating reflections from the front surface of dark-tinted lenses.

Our eyes see things in different ranges of vision — from distance to arm’s length to near. As we age, it becomes more difficult to adjust focus from one range of vision to another. Progressive lenses allow you to see all ranges of vision clearly, progressive lenses reveal a better range of vision.
Progressive lenses are perfect for seeing clearly across all distances. There is a seamless transition between distances and there is no more “jumping” of images when going between the top and bottom half of the lens. Plus, progressive lenses appear clear throughout, unlike the distracting lines of a bifocal lens.
Bifocal lenses only allow you to clearly see far away and up close. Objects at arm’s length will still appear blurry. Additionally, there is an abrupt change between the near and far viewing areas. Not only does this make transitioning between ranges difficult, it gives the lenses unattractive lines in a half-moon shape.
Can be customized with any other lenses categories as anti-reflection, trivex …etc

Trivex lenses are the safest lenses on the market; they are made of an exceptionally clear, lightweight lens material, so you can experience superior eye protection, sharp vision and lightweight comfort, all in the same lenses. Trivex lenses, are available in a wide variety of lens designs.
It’s always smart to choose a lens based on its strength and safety profile — particularly for protective eyewear for kids, sports eyeglasses and sunglasses. Trivex lenses excel in this regard.
Trivex lens material was originally developed for use by the military in helicopter windshields and fighter jet canopies. Then, in 2002, PPG Industries tailored the chemistry of the material specifically for use in optical lenses, making Trivex one of the most lightweight, impact-resistant eyeglass lens materials available.
Trivex lenses tend to cost more than polycarbonate or standard plastic lenses. But if you want what many eye care professionals consider to be the best combination of safety, comfort, appearance and optical performance for most eyeglass prescriptions, the Trivex price tag may be an investment worth making.