Water content is one of the most important parameters when choosing quality contact lens. Water content also is an important factor of the various plastics which are used to make soft contact lenses. In the cases of conventional soft contact lenses, higher water content of a contact lenses can let more oxygen pass through the lens to the surface of the eye. So this is important for lens comfort and healthy eyes.
However, high water content can be more fragile, so they are more likely to tear with frequent handling. A lot of contact lenses now contain between 50% and 60% water and some contain over 70%. But we cannot say that a high water content contact is much better that a low one, because in the cases of dry eyes, a low-water-content lens is better, since the low-water content lens holds its shape better in dry environments and fits better, and it is also less dependent on absorbing your tears to maintain its shape.
How much water do contact lenses contain?
Depending on the water content, contact lenses can be divided into three groups. Each group means a slightly different quality in contact lenses. Do you know which group your contact lenses belong to?
- High water content (up to 75%) – Contrary to popular belief, lenses with a high water content attract the tears of the eye and thus make them more susceptible to drying out. The higher the water content of a contact lenses, however, the more oxygen reaches the cornea. In addition, contact lenses with a high water content are considered to be easier to handle when inserting, removing, cleaning and disinfecting.
- Mid water content (up to 60%) – Hydrogel contact lenses with a medium water content are suitable for most lens wearers. They allow oxygen to flow to the cornea without absorbing the water of the natural tear film.
- Low water content (up to 40%) – Soft contact lenses with a low water content level of about 38% feel comfortable and let your eyes breathe without drying them out.
How can I find out water content in my contact lens?
Basically, you’ll be able to find the water content percentage displayed on the packaging of your contact lenses. The percentage of water content that you see in the contact lens product packaging is displaying the percentage size of the lens in absorbing water in the nearby areas. It is not the amount of water contained in the contact lens. In the product packaging, you’ll also spot the components that make up the rest of the lens and the material used to design the surface of the lens.
Which water content is the best for you?
High water content lenses are generally not the best for dry eyes. Contact lens wearers who are more prone to dry eye syndrome will find contact lenses with lower water content more comfortable to wear. If you suffer from dry eyes, soft contact lenses with a high water content may be problematic for you, as they absorb the eye’s natural tear film. Therefore advises you to wear silicone hydrogel lenses, which combine the advantages of contacts with a lower water content and superior oxygen permeability.
With high water content lenses, the moisture in the lens draws out the eye’s tears, making them more prone to dehydration. High water contact lenses are also more likely to become dehydrated due to everyday environmental factors such as excessive screen use and air conditioning.
Wearing soft contact lenses can dry your eyes out due to modern-day living. This is known as contact lens induced dry eyes (CLIDE) and is slightly different to dry eyes syndrome. It occurs because the thin layer of contact lens material on your cornea limits oxygen flow to the eyes. Without a steady flow of oxygen, your eyes struggle to develop natural tears.
Silicone hydrogel contact lenses are a popular choice for those with more sensitive eyes as they allow more oxygen to pass through the material than standard hydrogel material. They also have a higher oxygen transmission which means that eyes will stay fresh and healthy throughout the day. The material keeps your eyes hydrated so that they don’t get dry as easily.
Some people refer to the oxygen permeability of contact lenses as the DK/t value. The unit of measurement for oxygen permeability through a contact lens depends on the thickness of the lens. Gas permeable contact lenses are usually classified according to their DK/t value. These lenses do not contain high-water content.
Your optometrist will prescribe you the best lenses for your eyes, and if you have particularly dry eyes, then you’ll most likely be prescribed mid-water type lenses due to their versatility and comfort. Let’s book an appointment with us at Malaya Optical Optometrist to know what are the best lenses for your eye.