Contact lenses are a very good choice for people who needs vision correction but don’t want to wear glasses, or undergo LASIK surgery. To know if contact lenses are the right choice for you, read on about types of contacts lenses.
Types of Contact Lenses: Materials
If we classify contacts based on material, there are five types of contact lenses.
Soft lenses
Soft lenses are made of plastics called hydrogels. These contact lenses are thin and pliable, and have ahigh water content. They can conform to the surface of the eye, for greater comfort.
Silicone hydrogel lenses
These lenses are a special type of soft contact lenses that are more porous than regular soft lenses. They allow even more oxygen to reach the cornea, and provide more comfort. They are one of the most popular types of contact lenses worldwide.
Gas permeable lenses
Also called GP or RGP lenses are rigid contact lenses. They look like the older, less comfortable PMMA lenses, but are more porous than the latter. For this reason, they allow more oxygen to diffuse to the cornea, resulting in greater patient comfort. Because of this, nonporous PMMA have been almost entirely replaced by these type of contact lenses. They provide sharper vision than soft and silicone hydrogel contact lenses, especially if you have astigmatism. Your eyes may take longer to adjust to GP lenses than soft lenses. However, after the initial period, you will find that RGP lenses are almost comfortable as the soft hydrogel lenses.
Hybrid contact lenses
These are a special type of contact lens, designed to provide the wearing comfort of soft or silicone hydrogel lenses, along with the sharper optics of gas permeable lenses. These contacts have a rigid gas permeable central zone, which is surrounded by a “skirt” of hydrogel or silicone hydrogel material. These lenses are difficult to fit and need specialist training, and are also very expensive. For this reason, these types of contact lenses are limited for use in patients with high astigmatism.
PMMA lenses
These hard plastic are made from rigid plastic material called polymethyl methacrylate (PMMA). This type of lenses provide sharp vision, but do not transmit oxygen to the eye very well. For this reason, they are less comfortable. You may not find them easy to adapt to. This type of “hard contacts” have largely been replaced by RGP lenses.
Types of Contact Lenses: Wearing Time
Most contact lenses have to be removed and cleaned at night. Extended wear lenses however, allow you to sleep in them. Therefore, the two types of contact lenses as classified by wearing time are:
- Daily wear: which must be removed before sleeping
- Extended wear: which can may be worn overnight, usually for up to a week, without removal
- Continuous wear: are a special type of extended wear contact lenses, which can be worn for up to 30 consecutive nights without removal.
Types of Contact Lenses: Lens Replacement Frequency
These contacts are classified depending on when they need to be replaced: that is the lens replacement frequency.
- Daily disposable lenses: Safest type of contact lenses. Must discard after a single day of wear
- Disposable lenses: Must discard after every two weeks, or sooner, depending on brand
- Frequent replacement lenses: May be used for 30 to 90 days, that is discard monthly or quarterly, depending on brand
- Traditional ( also called reusable) lenses: May be used for up to a year, usually discarded after every six months
