Contact Lenses Types Explained!

Various types of contact lenses are available now to correct all types of refractive errors, such as myopia, hyperopia, astigmatism, aphakia and presbyopia. A thorough eye examination is recommended to determine the type of contact lenses that is ideal for you. In general, there are three types of contact lenses made from different materials:

• Soft contact lenses (hydrogel plastic polymers)

• Hard contact lenses (polymethyl methacrylate - PMMA)

• Gas-Permeable contact lenses (plastic, silicone or fluoride materials).

Soft Contact Lenses

Soft contact lenses are the most popular and comfortable contact lenses. Soft contact lenses can be used to correct myopia, hyperopia, astigmatism, presbyopia and even bifocals. Soft contact lenses are large where the edge of the contact lenses extends beyond the boundary of the cornea. Soft contact lenses are composed of 38-80% water. The main advantages of soft contact lenses are comfort and ease of adaptation. However, the disadvantages of soft contact lenses are fragility, greater risk of biological contamination and greater care and maintenance.

Soft contact lenses are available on 'extended-wear' and 'disposable' types. Extended wear is worn for one week without removal and then discarded. Soft contact lenses can be worn on an extended-wear basis due to the lens are very thin and high water content. Disposable soft contact lenses are worn on a daily basis and they are cleaned and disinfected daily. They are discarded after two weeks of wear. Today, you can even find daily disposable contact lenses that are designed to be worn for a day and then thrown away. The advantages of disposable wear are better ocular health and minimal care. 

Hard Contact Lenses

Hard contact lenses (also known as rigid contact lenses) has smaller diameter compared to soft contact lenses.  It is used for people with serious astigmatism problem. Hard contact lenses do not flex on the cornea. Essentially, it deprives the cornea of adequate amounts of oxygen. Hard contact lenses are commonly associated with corneal irritations and abrasions. Moreover, they cause eyes to dry out hence are more likely to be lost during rough sport activity. However, hard lenses are more durable and require minimal care and maintenance compared to soft contact lenses.

Gas-Permeable Contact Lenses

Gas-permeable lenses (also known as "semi-soft" or "rigid gas permeable, RGP") have similar design to hard contact lenses. But they tend to flex more hence they allow more oxygen to transmit through the lens to the cornea. Due to greater oxygen transmission, initial adaptation is easier. As a result, gas-permeable contact lenses are preferred to hard contact lenses. Today, gas-permeable lenses also available on extended-wear due to recent advances in polymer technology.

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