Do you know how contact lenses are made? Contact lens manufacturing 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.
Contact lens manufacturing process
1. 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.
2. 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 for increasing the water content and therefore contact lens 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.
2. Silicone Hydrogel
Silicone Hydrogel is the latest material for the production of contact lenses, which gives much more oxygen permeability compared to the regular hydrogel. It’s a combination of hydrogel and silicone, fluoro silicone, 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.
This 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
This 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：https://ukdiss.com/examples/contact-lens-development.php
How to make contact lenses, through the following introduction video, you will understand more clearly.