Water content of contact lenses

The water content of a contact lens is the percentage of water present in the lens material. Soft contact lenses are made from hydrogel or silicone hydrogel, materials that can absorb and retain water. This water content is expressed as a percentage of the lens’s total weight.

Most soft lenses have a water content of between 30 and 80 per cent. Lenses with a lower water content (30–50 per cent) are often referred to as low-hydrogel lenses, whilst lenses with a higher water content (50–80 per cent) are known as high-hydrogel lenses.

The water content helps determine how a lens behaves on your eye. Lenses with a higher water content often feel softer and more supple, but they can also draw moisture from your tear film more quickly. Lenses with a lower water content retain their shape better and evaporate less quickly, but may feel a little stiffer at first.

Silicone hydrogel lenses often have a lower water content than traditional hydrogel lenses, as the silicone material allows oxygen to pass through without requiring much water. This enables these lenses to combine good comfort with high oxygen permeability.

Water content and comfort

There is a common misconception that a higher water content is always better for comfort. In practice, comfort depends on several factors: the amount of tears you produce, the composition of your tear film, how long you wear the lenses and the environment in which you use them.

Lenses with a high water content can draw moisture from your eye during prolonged wear or in a dry environment in order to maintain their own moisture balance. This can actually lead to a dry sensation. Lenses with a lower water content evaporate less quickly and may therefore be more comfortable for some people, particularly when worn for longer periods.

Water content and oxygen permeability

With traditional hydrogel lenses, oxygen is mainly transported to your cornea via the water in the lens. A higher water content therefore often means better oxygen permeability. With silicone hydrogel lenses, the process works differently: the silicone material itself allows a great deal of oxygen to pass through, meaning that a lower water content does not pose a problem for oxygen supply.

Water content and lens care

The water content also affects how you care for your lenses. Lenses with a higher water content absorb moisture and fluid more easily, but also deposits and contaminants. They therefore often require careful cleaning and rinsing. At SMEYEL , you’ll find various types of lens solutions suitable for lenses with a range of water contents.

Choosing based on water content

Your optician or optometrist does not choose a lens based solely on its water content, but considers the overall picture: your eye characteristics, your tear film, your wearing pattern and any sensitivities you may have. Water content is one of the factors taken into account in that choice, but it is not the only one.