Contact lenses when looked at, they don’t appear to be more than tiny silvers of plastics. But contact lenses are a highly sophisticated combination of technological design and advanced materials. The process of Manufacturing contact lenses0 depends on whether the lenses are soft contacts, rigid gas permeable contacts or hybrid lenses.
Soft contacts are made of pliable hydrophilic plastics called hydrogels. It absorbs significant amounts of water to keep the lenses soft and supple. The water content of soft lenses allows oxygen to pass through the lenses and keep the cornea healthy during contact lenses wear. It is important to keep in mind that different brands of soft contact lenses have different water contained and lens thicknesses. Hydrogen materials used for soft contact lenses is their surface charge, which can affect how quickly proteins deposits form on the lenses during wear. Let's discuss the method of manufacturing soft contact lens.
1: Injection moulding – During this process, the soft contact lens material is heated to a molten state and is then injected into a computer-designed mould under pressure. After that, the lenses are quickly cold and removed from the mould. The edges of the lenses are polished smooth and the lenses are hydrated to soften them before undergo a quality assurance test. Since it is faster and less expensive than the lathe cutting process, most of the disposable contact lenses are made with an injection moulding process.
2: Lathe Cutting – In a lathe cutting, a cylinder of contact lenses material is inserted in a machine that will rotate incredibly fast. Then, the material is still dry and hard. A diamond grinder will cut the proper diameter for your lenses and will carve the inside of the lenses to fit your cornea. This piece of material will be glued to a piece of metal so it can be mounted on a second grinding machine, which will help to cut the outsider curvature of the lens precisely. The glue is removed and the quality of the lenses is then tested, and the dry pieces are hydrated, expanding them to your full size and then they are packaged finally.
3: Cast moulds – The most dominant manufacturing process of soft lenses is cast moulding. In this cast moulding contact lenses process, there are two parts of the mould, anterior and posterior mould. The monomer is added into the posterior mould and it is then capped with anterior mould, forming a curved shape of the lens. The polymerization is initiated by ultraviolet light as the mould travels along the production line and the lenses hardened.
The material and manufacturing processes have constantly evolved to create greater comfort for wearers, reduce cost and increase production efficiency.