Plastic lenses have good optical quality. They are about half the weight of glass lenses, shatter resistant and economic. The lenses are hard coated to protect from scratches. They can be easily tinted or UV coated as they do not have in-build UV protection. Suitable for most prescriptions and frame styles. 

If you have a strong prescription and wish to have thinner and lighter lenses, choose high index lenses. These lenses  are up to 40 percent thinner and lighter than a regular lens . They are more comfortable to wear and make glasses look cosmetically better. They have in-built UV protection.

If you participate in sports or have a job that carries the risk of breaking the lens, the best option is a polycarbonate lens. It is the lightest lens available, most impact resistant,  with in-built UV protection. Highly recommended for children's eyewear. Ideal for rimless frames, as it will reduce the possibility of lens damage.