Although there are many ways to categorize contact lenses, they can be classified into two basic types according to their chemical composition and physical properties: soft and rigid.
Soft lenses
Soft contact lenses have become the most popular type of lenses. As their name suggests, they are pliable and made of materials that allow them to absorb and hold water, as well as permit oxygen to pass through the lens to the cornea. Soft contact lenses can be further classified into daily wear, extended wear, and disposable lenses. Specialty lenses are also available, such as toric lenses, multifocal lenses, and cosmetic tints. The PuriLens System may be used with any type of soft contact lens.
Advantages of soft contact lenses
- They provide maximum comfort and require a short adjustment period
- They can generally be worn for more hours during the day
- They are easy to insert and remove
- For people with an active lifestyle, soft lenses are an excellent choice as they are unlikely to fall out during vigorous physical activity (however, contact lenses should not be worn while swimming).
- Vision may not be as crisp as with rigid lenses
- If not properly cleaned, they tend to accumulate more protein deposits than hard lenses
- They require special care, may tear, and have a shorter life span than rigid lenses
The vast majority of rigid lenses today are known as rigid gas permeable (RGP) lenses because they are made of materials that allow oxygen to pass through the lens to the cornea, increasing comfort and safety.
Advantages of RGP lenses
- RGP lenses may provide higher vision quality than soft lenses
- RGP lenses allow oxygen to pass through the lens to the eye, providing greater comfort than traditional hard lenses
- They can be worn for longer periods of time than traditional hard lenses
- RGP lenses require a longer adjustment period than soft lenses
- Because they are rigid, they may fall out during physical activity
- They may require use of special wetting solutions to maintain comfort