Contact lenses (contactlens), also known as corneal contact lenses, are lenses worn on the cornea of the eye to correct vision or protect the eye.
According to the material hard and soft it includes hard, semi-hard, soft three.
History of materials
1. Rigid lenses: PMMA polymethylmethacrylate was invented in 1934; the first all-plastic contact lenses were made from PMMA in 1947.
Advantages: better vision correction, longer lens life;
Disadvantages: brittle, poor gas permeability, strong foreign body sensation.
2. Soft lenses: discovery of PHEMA hydroxyethyl methacrylate in 1960; first soft contact lenses (Otto Wichterle, father of soft lenses); FDA approval in 1971.
Advantages: soft, oxygen permeable, comfortable, no foreign body sensation;
Disadvantages: prone to adsorption and precipitation, short life.
3. Rigid gas permeable lenses (RGP): born in 1970 and patented by Polycon in 1972, the material is mainly made of PMMA polymerized with silicone.
Advantages: good oxygen permeability, lower hardness than PMMA;
Disadvantages: lack of comfort.
Contact lenses belong to several classes of medical devices
According to the risk assessment of product safety, because contact lenses are in direct contact with the eyes, potentially hazardous to the human body and its safety and effectiveness must be strictly controlled, so contact lenses are classified as class III medical devices.
Medical Device Classification
The medical device class requirements for hospitals can be divided into three categories: Class I, Class II, and Class III.
First, Class I refers to the routine management of medical devices sufficient to ensure their safety and effectiveness;
Second, Class II refers to its safety and effectiveness should be controlled medical devices;
Third, Class III refers to the implantation of the human body, used to support and maintain life; the human body has a potential risk and its safety and effectiveness must be strictly controlled. must be strictly controlled medical devices. If a medical device contains Class I and Class II, then this medical device is Class II. If a medical device contains Class II and Class III, then this medical device belongs to Class III.