Hydrogels Contact Lenses

Abstract

Contact lenses can be classified in a number of ways; however, the two main categories are hard and soft lenses, which are based on the material used for their manufacture. The soft lens category can be further divided into hydrophobic and hydrophilic subcategories. Consequently, the development of contact lens materials took three specific directions: hydrogels with high water content, rigid gas-permeable lenses with enhanced oxygen permeability, and surface modification of silicone elastomer lenses. These polymeric systems are expected to improve the water content of the contact lenses as well as the permeability to oxygen, which are crucial properties but controllable through the molecular design. Currently, the high water content hydrogels are being challenged by the silicone-hydrogels for the world market share.