There are different types of contact lenses to fill different needs. If you are thinking about getting contacts, your eye doctor will recommend the best kind for your eyes.
Contact lenses fall into three main categories, depending on the materials they’re made of. They can be soft, rigid gas permeable (GP) or hybrid. Let’s look at each one separately.
Soft Contact Lenses
Soft contacts are made of supple water-loving (hydrophilic) plastics called hydrogels. Hydrogels soak up considerable amounts of water to keep lenses soft and pliable. The water content allows oxygen to pass through the lens to keep the cornea healthy while the contact lenses are being worn.
Hydrogel soft lenses are usually available in three categories, based on their water content, as follows:
- Low water content (less than 40 percent water)
- Medium water content (50 to 60 percent water)
- High water content (more than 60 percent water)
Different brands of soft contacts have different water content and thickness, with those that have low water content being thinner than those with high water content. This is because some people are more comfortable wearing thinner lenses and some like wearing thicker lenses.
Gas Permeable Contact Lenses
Gas permeable contacts (GP) or rigid gas permeable contacts (RGP) were originally made of a hard plastic called polymethyl methacrylate, which, while possessing excellent optical qualities, durability and biocompatibility, had no oxygen permeability. Many people couldn’t safely wear these lenses because of that.
Modern GP lenses are made of fluoro-silicone/acrylate and are optimized for oxygen permeability, lens stability and surface wetting characteristics. Some GP contacts can even be worn overnight.
GP lenses do not contain significant amounts of water but rely on their microscopically porous nature to let oxygen through to the cornea. Because of their hardness and the fact that they don’t fluctuate significantly in water content, gas permeable contact lenses usually have superior optical characteristics and provide sharper vision than soft lenses.
Despite this, some people can’t tolerate wearing rigid lenses and must choose soft lenses for comfort.
Hybrid Contact Lenses
Hybrid contact lenses are made with a rigid gas permeable lens in the center, surrounded by soft contact lens material. The idea is to provide the vision of a GP lens with the comfort that soft lenses provide. Several types of hybrids are available, including multifocal designs for presbyopia, hybrid contacts for keratoconus (irregular-shaped corneas) and other conditions.
Your eye doctor may suggest hybrid contact lenses if you have one of the following eye conditions:
- You have corneal astigmatism
- You experience lens rotation or fluctuating vision with soft lenses
- You’re interested in GP lenses but concerned about comfort
- You have presbyopia with astigmatism
- You wear soft multifocal lenses but want better vision
- You have irregular corneas
