Classification of contact lenses- materials, designs and specifications
Back in 1508 Leonardo da Vinci was the first one to propose the idea of contact lenses. Today, those are used to correct common vision problems in nearly 125 million people worldwide. Let's take a look at common classifications published in StatPearls by NCBI Bookshelf. First of all there are 3 anatomical positions for contact lenses: scleral (covers cornea, sclera, and conjunctiva), corneal (covers only cornea) and semi-scleral. Next there can be 3 grades of water content: low (0-40%), medium (40-55%), high (>55%). Based on wear time contact lenses and be for daily use, extended wear or disposable. And last but not least- the material. Earlier, contact lenses were made of glass. Over the years researchers have been looking for ideal material with a number of properties. Filcons- hydrophilic non-rigid lens materials and focons- hydrophobic rigid lens materials. More by the link!