In the optics manufacturing industry, contact lenses have brought a revolution. These days, we see many people, both men and women, using contact lens to correct nearsightedness, farsightedness and such other eyesight problems. This type of lenses is handy and easy to use compared to glass lenses which are heavy and brittle. With so many people using contact lenses worldwide, you may wonder how they are so accurately designed in spite of such bulk production every year.
You must remember there are two types of contact lens: soft contact lens and Rigid Gas Permeable lens. You need hydrophilic plastic polymers called hydrogels to make soft contacts. These materials easily absorb water and become soft and flexible without losing their optical abilities. Latest silicone hydrogel soft contact lenses include oxygen-permeable varieties.
The other type of lens is RGP or Rigid Gas Permeable lens made of harder materials for long-term use.
Contact Lens Manufacturing Process
The most popular and most cost-effective method for soft contact lens manufacturing is injection molding. In this process, workers heat the lens material to form a liquid which is then injected into pre-cut molds under pressure. Once the lenses get cooled, they are removed from the molds giving them specific shapes. Workers also polish the edges of lenses to make them smooth and hydrated before sending them for final quality check. However, please note that injection molding can only be used to manufacture soft contact lenses. This process helps you create contacts at a faster pace. It is even less expensive than the lathe cutting method mentioned below.
In this process, the lens material is individually mounted on rotating shafts and shaped with precision cutting tools. After shaping the front and back surfaces, workers remove the lens from the lathe and polish and hydrate it before quality inspection. Compared to injection molding, lathe cutting involves more steps. However, with time, use of advanced tools and technologies make this process less time-consuming and less complicated. Lathe cutting is perfect for shaping more complex lenses such as RGP contact lens.
Materials Used to Make Contact Lenses
For Soft Contacts
You can use hydrogel for soft lens manufacturing. It is a water absorbing polymer that uses the water content to send oxygen to the eye through the contacts.
Grade Hydrogel lenses have varying capacity to soak water. There are some lenses that can hold up to 70% of water. When a lens absorbs water, automatically its size increases causing discomfort to the users. Thinner contacts have low water content.
Silicone Hydrogel is the latest type of soft lenses having more oxygen permeability and low water content.
For Hard Contacts
You need hard polymer (plastic) for hard lens modeling, which is naturally permeable to allow oxygen to reach your eyes. Hard plastic gives more optical clarity and can easily send oxygen from one side to the other.
To enhance oxygen permeability in contacts, scientists use fluorine, which allows people to wear hard lenses for a long time.