How does Contact lens manufacturing

Do you know how contact lenses are made? Manufacturing contact lenses is a complex process involving cutting, quality testing, sterilization and other processes.

The manufacturing process also involves the choice of materials, Production technology, etc. In this article, we will briefly introduce the production process of contact lenses and the introduction of related manufacturing materials.

The two main production processes technology is Semi-molded manufacturing,Full molding process at present

Semi-molded manufacturing

The key step of semi-molded manufacturing is lathe cutting.Lathe cutting is the process of placing a small hard disk of contact lens material on a rotating shaft, like a miniature pottery wheel, which rotates at 6,000 revolutions per minute and is shaped with a computerized cutting tool. Once the lens is made, it goes through different stages of polishing and hydration, and then undergoes a quality assurance sterilization test. In this manufacturing process, the focus is on controlling human factors.

Contact lens process drawing

Full molding process

The full-molding process mainly uses precision molds to form contact lenses at one time through a numerical control mode. Mainly injection molding. Injection molding is the process of heating the soft contact material to a liquid state and then injecting it into a precise pressurized mold. After molding, polishing, moisturizing and quality assurance tests are performed.

Contact lens manufacturing materials

The basic material for the production of soft contact lenses is HEMA. This methacrylate allows increasing the water content and therefore contact lenses permeability to oxygen from its original value of 40% to about 80%. Currently, there is a new generation of soft contact lenses which uses silicone hydrogel. This material is used to produce contact lenses for continuous wear ,because of the high oxygen permeability. The disadvantage of soft contact lenses is the predisposition to produce contact lens deposits. Modern soft contact lenses were invented by a group of Czech chemists led by the scientist Otto Wichterle.

Silicone Hydrogel is the latest material for the production of contact lenses, which gives much more oxygen permeability compared to regular hydrogel. It’s a combination of hydrogel and silicone, fluorosilicone, which manages to increase the oxygen permeability, even with a low volume of water. This compound combines the qualities of soft and hard contact lenses. The disadvantage of these lenses is the lower level of wettability and tendency to contact lens deposits.

Wettability is the tendency of one fluid to spread on, or adhere to, a solid surface in the presence of other immiscible fluids. Contact lenses made from silicone rubber (hydrophobic material) rarely achieve sufficient wettability of the material, which is necessary to slip the contact lens on the eye

The oxygen permeability is given with the value “Dk/t”. The longer the lenses remain on the eyes, the more oxygen permeable they should be. If the value is too low, redness, or itching and burning may occur in sensitive eyes.

Contact lens materials have undergone continuous development and technological updates. At present, the mainstream contact lens materials are silicone hydrogel and HEMA.

Please read this article for specific material development history:

How to make contact lenses, through the following introduction video, you will understand more clearly.