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What does the water content of a contact lens mean?
Medically reviewed by Sharon Copeland on 8 December 2020
The water content of a contact lens means precisely that – how much of the contact lens is made up of water. This figure is always given as a percentage.
The higher the water content in a contact lens, the more oxygen reaches the cornea during lens wear. This is important for healthy eyes.
The relationship between water content and oxygen transmission is not the same with lenses made with silicone hydrogel materials. These contact lenses achieve very high levels of oxygen regardless of their water content.
Most contact lenses today are made from a soft plastic known as hydrogels. Hydrogels absorb a larger amount of water to keep the lens soft. The absorbing power of hydrogel material is also known as water content.
How can I find out the water content of my contact lenses?
Usually, you'll be able to find the water content percentage displayed on the packaging of your contact lenses. Here, you'll also see the components that make up the rest of the lens and which material makes the lens.
To find out the water content of your contact lenses, or the lenses you're looking to buy, why not take a look at our contact lens specification table.
Does the water content percentage affect the comfort level of my lens?
A higher water content generally means a thicker lens, which can often be felt in the eye. Nowadays, mid-water lenses, which are thinner and more widely worn, offer a greater degree of comfort to those who wear contacts. The general design of the lens and the smoothness of its edges will be a major contributing factor to the comfort on the eye.
Is higher water content in contact lenses better for dry eyes?
High water content lenses, contrary to popular belief, 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.
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 optician 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.
Following a good eye care routine can certainly benefit your eye health as can following a healthy diet. If you suffer from dry eyes using eye drops will help to relieve you of any discomfort. Our comfi Drops work to rehydrate and lubricate your eyes throughout the whole day.
What should the water content be for contact lenses?
The amount of water in contact lenses varies depending on the type of lens. For those who wear soft contact lenses, the water content ranges from 38 to 75 per cent.
Soft contact lenses are usually available in three categories: Low water content contact lenses containing less than 40 per cent water, medium water content containing 50 to 60 per cent water and high water content contact lenses containing more than 60 per cent water.
What are soft contact lenses made of?
Soft contact lenses are made of pliable hydrophilic. These are water-loving plastics called hydrogels. Hydrogels absorb large amounts of water to keep lens material soft and supple, thereby aiding comfort. Soft, flexible plastics include a silicone hydrogel material. This is silicone and hydrogel to help increase (oxygen transmissibility). Silicone hydrogel lenses are new and are very popular as the material transmits up to six times more oxygen to the cornea. This makes them safe for use as extended continuous wear lenses. They are considered to be better for your eye health as they decrease the risks of hypoxia. A condition when the corneal oxygen supply is significantly reduced.
Quick links:How dehydration impacts your eyes
A guide to dry eyes
What are silicone hydrogel contact lenses?