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 ophthamologists. 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:
Contents
- Definition
- Types of soft contact lenses
- Contact lens polymers hydrogel and silicone hydrogel materials
- History
- FDA groups and brands
- Production generations
- References
Definition
The U.S. Food and Drug Administration (FDA) states that:
Soft contact lenses are made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses may be easier to adjust to and are more comfortable than rigid gas permeable lenses. Newer soft lens materials include silicone-hydrogels to provide more oxygen to your eye while you wear your lenses.
Types of soft contact lenses
The U.S. Food and Drug Administration (FDA) 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 ("-filcon"):
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 (hydrogel and silicone hydrogel materials)
The materials that are classified in the four (4) FDA groups include the ones listed in the next 4 sections:
History
The first contact lenses were made of a polymer called polymethylmethacrylate(PMMA) and became available in the 1960s. Lenses made of PMMA are called hard lenses. Soft contact lenses made of polyacrylamide were introduced in 1971.
FDA groups and brands
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 Permeability rating, the more oxygen gets to the eye.
Production generations
There are three generations of silicone hydrogel contact lens materials: