Sunglasses come in non-prescription and prescription sunglasses. They both benefit eye by protecting them from sun. The tint on a pair of sunglasses is irrelevant to protection that it offers.

Children as well as adults should wear sunglasses. The ultra violet damage occurs over time, therefore, a person needs to protect eyes at an early age. Also children's eyes are more sensitive that that of an adult. The bottom line is that while wearing sunglasses is a fashion statement, they have a specific function-to protect your eyes from sunlight.

The Trifocal Lens-meaning they have three focal views-is designed similar to bifocal lens with exception to center focal point on lens is for intermediate vision.

The fourth type of lens is Multi Focal lens. It has more than one focal view; therefore a Bifocal and a Trifocal are types of multi focal lenses.

Other types of lenses that are specially designed for other purposes include Computer Lens. They are designed so that when sitting at a computer, a person can view monitor and papers nest to monitor at same time. And then there are Double Bifocals, which are rarely prescribed, but when they are it is usually for pilots, electricians or other professions that need to have close vision overhead.