For an overview, read on to know how different types of contact lenses are made.
How Soft Contact Lenses are Manufactured
Soft lens are manufactured from hydrophilic plastic polymers called hydrogels. These lenses are the most popular of the different types of lens as they are highly water absorbent, soft and comfortable to the eyes with high optical qualities. The soft contacts with high oxygen permeability, the widely used silicone hydrogel are manufactured by the lathe cutting process or an injection moulding process.
In the lathe cutting process, spinning shafts are used to mount the non-hydrated disks of soft contacts material one by one. They are shaped intricately with computer tools that are used to cut the front and back surfaces of the contacts with precision and care. After the contacts is rendered to the required shape, it is removed from the lathe. The next step is to hydrate the lens and soften it. After it passes the quality assurance test, the contact lens is ready to be packaged.
The lathe cutting process involves more intricate steps and takes more time than the injection moulding process. However, in the recent years, as a result of new and scientific research going on in the relative field, it is now more automated and quick than it was in the earlier times. With the advent of automated robotics and the help of computerised processes, a lathe-cut soft contact lens can be now produced in a few minutes.
This process involves heating the soft contact lens material and transforming it into its molten state. After that, it is shaped in a particular way by injecting it into computer-designed moulds under high pressure. After it is cooled down, the material is removed from the moulds. They are given a finishing touch by polishing the edges smooth. After that, the lenses are hydrated so that they become soft. The last step is the quality assurance testing.
Soft disposable contact lenses are made mostly with the help of the injection moulding process as it is faster and more economic than the lathe cutting process.
How Gas Permeable are Manufactured
RGP (Rigid Gas Permeable) are made from oxygen-permeable plastic polymers constituting silicone and fluorine. They are quite different from the soft hydrogel contact lenses as they have less water content and are more rigid than the ordinary soft contact lenses. Gas permeable lenses, as opposed to soft contact lenses are custom-made specifically to the prescription of the patient. This customisation is needed as rigid contact lenses have a particular shape and do not conform to the eye as soft lenses do. Even a minute difference can cause discomfort and the user might fail to get a comfortable fit. This makes them a bit costlier than the soft contact lenses that are mass-produced.
The RGP contact lenses are manufactured in a process similar to that used for lathe-cut soft lenses. The lathe cutting process is carried with precision using computerised processes. These lenses are soaked in a GP contact lens care solution before the Optician dispenses them to the patient. This solution is vital for conditioning the lens surface for the comfort of the wearer.
How Hybrid Contact Lenses are Manufactured
Hybrid contact lenses possess a central optical zone made of rigid gas permeable plastic while the surrounding peripheral area is made up of soft contact lens material for the comfort of the user.
The process of manufacturing of these lenses is similar to lathe-cut soft contact lenses manufacturing process. However, there is one major difference. The soft plastic discs have a rigid gas permeable center. This area is surrounded by soft lens material that is not hydrated. Advanced and proprietary technology is used to bond the two materials together such that even after the lens is hydrated, they stay together.