What is Oxygen Permeability in lenses?
A striking difference between the contact lens and the glasses is freedom. While they both give great vision, comfortability differs. However, with this freedom comes a little problem.
Your eyes need to breathe just like every other part of you. Wearing contacts cuts down the oxygen level your cornea absorbs, leading to fatal results and adverse reactions.
In this article, we’ll look at oxygen-permeable contact lenses, their types, and their benefits.
What is Oxygen Permeability in Contact Lenses?
Oxygen permeability in contact lenses is the ability of your lens material to allow oxygen to pass through, reaching your cornea. The cornea has no blood supply and relies on oxygen from the air to maintain its health and functionality.
Oxygen permeability in contact lenses is known as DK.
D equals the diffusivity of oxygen through the lens material.
K equals the solubility of oxygen in the lens material.
When you have a higher DK value, you have a higher level of oxygen permeability.
The Importance of Oxygen for the Cornea
Your cornea is the transparent dome-shaped part of your eyes. It covers the iris and pupils. The cornea has no blood vessels and relies on oxygen from its surrounding environment.
Below are reasons why oxygen is vital for the cornea:
- Maintain Transparency
When there is insufficient oxygen supply to the cornea, you witness corneal swelling known as edema. In edema, the cornea becomes cloudy and results in impaired vision. An adequate oxygen supply ensures that your corneal cells remain healthy and transparent for good vision.
- Prevention of Corneal Hypoxia
Insufficient supply of oxygen can lead to corneal hypoxia. Having severe hypoxia can lead to worse complications. There are chances of edema – swelling of the corneal tissue. There’s also neovascularization- the growth of new blood vessels into your cornea. This growth happens as a response to chronic oxygen deprivation. While the growth of new blood vessels aids breathability, it can compromise your corneal transparency leading to vision problems.
- Supporting the Tear Film
Your tear film covers the cornea and provides the necessary lubrication and protection. An adequate oxygen level helps to maintain a healthy tear film. This maintenance occurs by supporting the epithelial cells that produce mucins, an essential tear film component. A healthy tear film prevents you from irritation, dryness, and infections.
- Promotes Healing
It is possible to have a scratch on your cornea say after surgery or even have an injury to your cornea. You need oxygen for the healing process. Oxygen helps close wounds and regenerate damaged tissue. It also helps to maintain the strength and structure of your cornea.
- Prevention of Infections
If your cornea receives enough oxygen, it becomes resistant to infections. Oxygen helps to maintain the epithelial barrier’s integrity which in turn protects the cornea against any microbial invasion.
- Comfort for all Contact Lens Wearers
Several contact lens wearers experience discomfort, dryness, and redness with their lenses. Most times, it results from low-oxygen permeable lenses. Such lenses create a barrier between the cornea and oxygen. However, when you have a high oxygen permeable lens, your cornea receives adequate oxygen keeping you comfortable at all costs.
Types of Contact Lenses and Oxygen Permeability
Oxygen-permeable lenses are solutions to your eyes’ breathing. Let’s look at the various types of oxygen-permeable contact lenses.
- Silicone Hydrogen Lenses
These are soft contact lenses made from silicone and hydrogel providing you with a high oxygen permeability. Silicone allows more oxygen to pass through regardless of water content.
Some examples of silicone hydrogel lenses you can purchase include Biofinity and PureVision.
Silicone hydrogel lenses have been the most prescribed type of contact lenses in recent years. Some of the benefits attached include:
- They are inexpensive
- They transmit oxygen up to 5 times better than conventional lenses
- They are comfortable to wear
- Only a few people have adverse reactions to it.
- They are your ideal lens for extended wear.
- Rigid Gas Permeable (RGP) Lenses
RGP lenses are made from durable plastic materials that are rigid but also permeable to gasses. They have a high oxygen permeability and ensure sharp vision correction. Some of the benefits include:
- Their small diameter allows for a more natural tear exchange under the lens.
- It provides sharp vision, especially for those with astigmatism
- It is less expensive.
There could be limitations, and some of them are:
- The lens is not so easy to order online
- It takes a lot of time to get used to the lenses
- Hybrid Lens
These hybrid lenses combine the features of both the silicone hydrogel and RGP lenses. It has a central RGP zone and a silicon hydrogel skirt. A major benefit here is the visual clarity of the RGP lenses and the comfort of the silicone hydrogel. The major downside is the cost – it is expensive.
Considerations in Oxygen Permeable Contact Lenses
While purchasing a high oxygen permeable lens, there are a few things to consider;
- Wear Time and Lifestyle
Wearing your lenses only during waking hours and being removed at night calls for either the RGP or silicone hydrogel. However, if your lenses are worn continuously including overnight, you need a high oxygen permeable lens, making the silicone hydrogel your optimal choice.
Another thing to consider is the wearer’s lifestyle. An athlete may benefit more from lenses with high moisture retention and oxygen permeability.
- Individual Needs and Factors
You must consider your health history, such as corneal issues, dry eyes, or sensitivity. If you have such issues; you need lenses with higher oxygen transmission and additional moisture-retaining properties.
Your refractive error can also influence your lens choice – myopia, hyperopia, astigmatism, and presbyopia. Don’t forget allergies and conditions that may require specialized lenses. The hybrid lenses come in handy in such cases.
Conclusion
In your selection of contact lenses, oxygen permeability is a critical factor. It plays a large role in the health and comfort of your eyes. An oxygen-permeable lens will help you maintain corneal health by ensuring an adequate oxygen supply and preventing conditions such as edema, hypoxia, and neovascularization.
Ensure you speak and consult with your eye care practitioner while selecting your contact lenses for great eye health.
