The most cost-efficient and popular method used to manufacture soft contact lenses in bulk quantities is injection moulding. This method is widely used for plastic-based products such as toys. In the production of contact lenses, the lens material is heated to the point of melting. The liquid lens material is then injected into a pre-cut mould. The material solidifies to the shape of the mould once the lens material dries. The lens will be polished, then inspected to check its standard of quality. This particular process lacks the precision required to make hard and gas permeable lenses, hence, it’s only used for soft contact lenses.
Lathe cutting is used to manufacture both hard and soft lenses. It is however, the only way to manufacture rigid gas permeable lenses. Lens cutting uses a technique that puts the lens material on a rotating mount (similar to a miniature potter’s wheel), whilst a machine severs and sculpts away excess lens material to shape a perfectly cut lens. Although this process maintains a greater level of symmetry and lens accuracy, it requires a more complex degree of technology, time and resources in comparison to injection moulding. It does, however, mean that it is ideal for more complicated lens shapes and RGP contact lenses.
How do contact lenses work?