This material has excellent optics and scratch resistance but has the inconvenience of high weight and low impact resistance. Non-tempered glass is less impact resistant than plastic glass. It is twice as heavy as a plastic lens. By cause of width and weight, recommended only for moderate prescription powers. Glass is declining in popularity due to its disadvantages
A good election if you want the an inexpensive solution. Plastic lenses offer a similar optical clarity as glass lenses. Considering its thickness, it is a bad choice for high prescription powers. Scratch-resistant coatings can be employed in most plastic lenses giving them comparable scratch resistance to glass. To correct night vision, diminish glare and improve the perceptibility of wearer's eyes are available anti-reflective coatings. Plastic represent the most common lens material in the United States, accounting for over 50 percent of sales.
High index plastics
The thinnest spectacle lens possible and, therefore, the most attractive.Determined by refractive index, high index lenses vary from 20% to 65% slimmer than plastic lenses. Typically, the higher the refractive index, the thinner the lens and more expensive it will be. An Anti-reflective (AR) coating is necessary for the best optical performance and look.
It remains a good choice for those who need the lightest and most shatter resistant lenses possible. This material offers a vastly superior degree of penetration resistance compared with glass and high index lenses. It provides better protection than heat-treated and chemically treated lenses. Used in safety eyewear and sports like hunting as well as general purpose eyewear. This lenses are highly recommended for children's spectacles and on any occasion where eye safety is a primary concern. About 40% thinner and 30% lighter than normal plastic lenses. Almost 20 percent of all spectacles sold in the United States are made of polycarbonate.