Contact lens type and material
Soft contact lens
Soft contact lenses are made of plastic, but not plastic used in garbage bags or paper dishes. Instead, the soft lens is made of hydrophilic plastic. Hydrophilic plastic is a special water-absorbing plastic. As long as it absorbs a lot of water, it will remain soft and moist.
If you wear soft contact lenses, you may have noticed the properties of this plastic. If your lenses dry out, they will become brittle and even crack. As long as the plastic stays well and moisturized in your eyes or in the mirror box, it will remain flexible and soft.
In your eyes, this soft flexibility means comfort! When your lenses are dry, your eyes will begin to feel discomfort because they rely on moisture to maintain their position and flexibility.
Soft contact lenses are classified according to the amount of water they contain. They can be classified as high water level or low water level.
Soft contact lenses for a long period
Most long-wearing contact lenses are made of silicone hydrogel, which combines the water-absorbing plastic of soft lenses with silicone. Adding silicon to the hydrogel plastic keeps the lens moist and allows more oxygen to pass through the contact lens to the eye. This will keep your eyes healthy while using contact lenses. More water and oxygen reach the eyes is why this material is added to contact lenses that are worn for a long time.
Any contact lens needs to be used for the wearer to maintain contact during the day and night, and to keep the eyes breathing and moist. Silicone added to the lens can provide this function to achieve the best glasses health.
Hard contact lenses
Rigid contact lenses (RGP lenses) are also made of plastic. Unlike the plastic that makes soft contact lenses, hard contact lenses transmit oxygen without absorbing water. Instead, there are tiny holes in the RGP lens that allow oxygen to pass through. Therefore, RGP lenses are independent of their water content through their oxygen permeability. Today, most RGP lenses are made of three main materials: acrylic, silicone and fluorine.
RGP lenses are different from rigid lenses that were mainly made of acrylic a few decades ago. These old hard lenses, because there is not enough oxygen to pass through. Over the years, lens manufacturers have added silicon to increase oxygen permeability, and finally fluorine has been added to help keep the lens wet while still maintaining its shape. This shape retention property makes them useful as a treatment for correcting eye problems such as keratoconus (corneal deformation).
Hybrid contact lenses
Although more rare, there are still hybrid contact lenses that combine the materials of RGP lenses and soft contact lenses. These lenses have a combination of acrylate-silicone-fluororubber in the middle of the lens to provide a clear central vision, and the soft contact lens water-absorbing hydrogel around the edges can improve comfort.