The soft contact lenses available today are made of either hydrogel or silicone hydrogel. The question is: what’s the difference between these two contact lens materials?
The history of hydrogel contact lenses
In 1959, Czech chemists Otto Wichterle and Drahoslav Lím published a paper entitled “Hydrophilic Gels for Biological Use” in the journal Nature. By 1961, Wichterle succeeded in making the world’s first four hydrogel contact lenses.
In 1965, the National Patent Development Corporation (NPDC) purchased the American rights to manufacture hydrogel contact lenses. The NPDC then sublicensed these rights to Bausch + Lomb.
In 1971, the US Food and Drug Administration (FDA) approved the first use of Soflens, the hydrogel material manufactured by Bausch + Lomb.
What are hydrogel contact lenses?
Hydrogel contact lenses are made of a water-infused polymer known as hydrogel. Hydrogel is a thin and pliable material, allowing it to conform to the shape of the eye.
In the 1970s, doctors started to prescribe hydrogel contact lenses more often than other types of contact lenses due to their comfort and ease of use. This led to hydrogel contact lenses rising in popularity.
What are the advantages and disadvantages of hydrogel contact lenses?
Hydrogel contact lenses are comfortable, durable, and easy to use. Hydrogel has high biocompatibility to the human eye, which means our bodies do not produce a negative immunological response when exposed to hydrogel.
Hydrogel’s biocompatibility to the human eye makes it an excellent material for contact lenses. Hydrogel contact lenses contain large amounts of water, making them suitable for people with sensitive eyes, or for those who suffer from dry eye syndrome.
Unfortunately, the water in hydrogel contact lenses gradually evaporates, making them uncomfortable to wear for long periods. Hydrogel also has low permeability to oxygen, which the human eye needs to maintain its health.
The history of silicone hydrogel contact lenses
Manufacturers were able to improve the hydrogel polymers used in contact lenses over the two decades after the FDA first approved hydrogel contact lenses in the US. This improvement resulted in the introduction of silicone hydrogel contact lenses.
In 1998, Ciba Vision (now known as ALCON) introduced the first silicone hydrogel contact lenses in Mexico.
In 2002, the US started marketing silicone hydrogel contact lenses.
What are silicone hydrogel contact lenses?
The improvement of hydrogel polymers led to silicone hydrogel contact lenses. From the name itself, silicone hydrogel is a polymer that contains both hydrogel and silicone. Silicone is a gel-like polymer that has a high degree of flexibility, making it a superb material for contact lenses.
Like hydrogel, silicone hydrogel contains water. However, unlike hydrogel, silicone hydrogel is more porous and has increased oxygen permeability.
What are the advantages and disadvantages of silicone hydrogel contact lenses?
Silicone hydrogel has high oxygen permeability, so silicone hydrogel contact lenses allow much more oxygen to pass through the lens and reach the cornea. Compared to hydrogel contact lenses, silicone hydrogel enables five times more oxygen to reach the cornea.
Silicone hydrogel’s high oxygen permeability means contact lens wearers are less likely to suffer from corneal hypoxia or a lack of oxygen supply to the cornea.
Another benefit of high oxygen permeability is that silicone hydrogel contact lenses are much more suitable for extended or continuous wear.
However, since silicone hydrogel is more porous than hydrogel, silicone hydrogel contact lenses are prone to deposit build-ups.
Furthermore, not all contact lens wearers should wear silicone hydrogel contact lenses. People who are allergic to or have any sensitivity to silicone cannot wear silicone hydrogel contact lenses.
Conclusion: which contact lens material is best for you?
Hydrogel contact lenses are comfortable and easy to use. They also have high biocompatibility to the human eye, which means people can wear hydrogel contact lenses without suffering any ill effects.
Hydrogel contact lenses also contain more water than their silicone hydrogel counterparts, making them ideal for contact lens wearers who suffer from dry eye syndrome. However, this water gradually evaporates, making hydrogel contact lenses less suitable for extended or continuous wear.
Meanwhile, silicone hydrogel contact lenses’ high oxygen permeability prevents wearers from suffering corneal hypoxia. This level of oxygen permeability also enables people to wear silicone hydrogel contact lenses for extended periods.
The downside of high oxygen permeability is that silicone hydrogel contact lenses tend to collect deposits more quickly than hydrogel contact lenses. Moreover, people who are allergic or sensitive to silicone cannot wear silicone hydrogel contact lenses.
Keep in mind that neither hydrogel nor silicone hydrogel can be considered the “best” contact lens material. When it comes to contact lens materials, there’s no such thing as the “best”. Every eye is different, and all contact lens wearers have unique situations. What’s best for you may not be best for other contact lens wearers and vice versa.
Finding the best contact lenses means finding the right ones for your specific vision requirements. To do this, consult with your eye care professional first and follow their recommendations.
The information in this guide is provided only as a secondary resource. It is not meant to replace the advice of a licensed eye care professional.
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