High Index plastic lenses are a must for anyone who has a strong prescription. High Index materials make possible lenses that are thinner and lighter than conventional materials. High Index materials are available in three tiers (1.6, 1.67, 1.74), with each index being thinner than the last. These materials are available in virtually every lens design, and are recommended based on the strength of your prescription. These High Index materials may also offer a clear, ultraviolet ray or blue violet ray filter.