List of soft contact lens materials
Soft contact lenses are one of several types on the U.S. Market approved by the U.S. Food and Drug Administration for corrective vision eyewear as prescribed by optometrists and ophthalmologists. The American Optometric Association published a contact lens comparison chart called Advantages and Disadvantages of Various Types of Contact Lenses on the differences between them. These include:
- soft contact lenses
- rigid gas-permeable
- daily wear
- extended wear
- disposable
- planned replacement contact lenses.
Types
The U.S. Food and Drug Administration classifies soft contact lenses into four groups for the U.S. Market. They are also subcategorized into 1st generation, 2nd generation, and 3rd generation lens materials. These 'water-loving' soft contact lens materials are categorized as"Conventional Hydrophilic Material Groups :
| Group | Water Content | Percentage | Ionic/Non-Ionic |
| I | Low Water Content | Nonionic | |
| II | High Water Content | Nonionic | |
| III | Low Water Content | Ionic | |
| IV | High Water Content | Ionic |
Note: Being ionic in pH = 6.0 - 8.0". This chart was published in the FDA Executive Summary Prepared for the May 13, 2014 Meeting of the Ophthalmic Devices Panel of the Medical Devices Advisory Committee.
The FDA has been considering updating soft contact lens group types and related guidance literature.
Contact lens polymers
The materials that are classified in the 5 FDA groups include the ones listed in the next 5 sections:History
The first contact lenses were made of glass, in 1888. Initially the glass was blown but soon lenses were made by being ground to shape. For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex began to replace glass in contact lens manufacture. PMMA lenses were easier to produce so the production of glass lenses soon ended. Lenses made of PMMA are called hard lenses. Soft contact lenses were first produced in 1961 by a Czech chemical engineer Otto Wichterle using polyhydroxyethylmethacrylate a material that achieved long-term commercial application.Hydrogel groups
Below is a list of most contact lens materials on the market, their water percentage, their oxygen permeability rating, and manufacturer brands. Note that the higher the oxygen transmissibility rating, the more oxygen gets to the eye.Low water nonionic
High water nonionic
Low Water ionic
High Water ionic
Silicone hydrogel polymers
Production generations
There are three generations of silicone hydrogel contact lens materials:| 1st Generation | 2nd Generation | 3rd Generation | |
| Material: | Lotrafilcon A, Balafilcon A | Senofilcon A, Galyfilcon A | Samfilcon A, Comfilcon A, Enfilcon A |
| Features: | TRIS structures, plasma treated, high modulus | Modified Tanaka monomer, lack of coatings, higher Dk for water content | No TRIS structure, no surface treatments or wetting agents, breaks traditional water-Dk-modulus relationships |