Oxygen Flow and Contact Lens Comfort
Since contact lenses lie directly on top of the cornea, it is important that the lenses allow a sufficient amount of oxygen to reach the cornea. The more oxygen that is supplied to the cornea, the greater the comfort and the lower the risk of serious complications.Many new contact lenses are made with silicone, which increases the amount of oxygen that flows through a contact lens to reach the cornea. This has been great development for both patients and the contact lens industry. However, a contact lens that delivers high oxygen is not always the most wettable lens. In fact, when high-oxygen silicone lenses were introduced, they were very uncomfortable because they did not wet well, leaving patients with dry eye issues.
Wettability and Contact Lens Comfort
Wearing contact lenses becomes a challenge for people with dry eyes. Some eye doctors feel that contact lenses made with hydrogel plastics are more "water-loving" than lenses made with other materials. Hydrogel plastics seem to attract water. Contact lens manufacturers market these types of contact lenses to people with moderately dry eyes.Many doctors feel that single use daily disposable contacts (silicone or non-silicone) are the answer for dry eye patients. Dry eye patients are more successful with disposing their lenses on a daily basis and ridding themselves of potential lens surface deposits, excess mucus, dust or other environmental debris.
Oxygen Flow vs Wettability
Just because a lens is capable of not drying out as badly as another lens does not mean that the lens also delivers a safe amount of oxygen to the eye. Nor does the lens that delivers the highest amount of oxygen to the eye have the capability of keeping the eye moist.Today’s silicone-based contact lenses are much improved because they are coated with a chemical that makes the lenses extremely wettable. It is important to note that some studies show that silicone lenses actually decrease dry eye symptoms. This varies widely depending on the person, as tear film chemistry varies among individuals.
Most contact lens wearers find that the most comfortable lenses are those that deliver both high levels of oxygen to the cornea as well as being extremely wettable. Finding the perfect contact lens sometimes take a fair amount of trial and error, and a good amount of patience.
Source:
Schafer J, Barr J, Mack C. "A characterization of dryness symptoms with silicone hydrogel contact lenses." Optometry & Vision Science, 2003. Annual Meeting Abstract and Program Planner, American Academy of Optometry.
