Contact Lenses Explained

Contact lenses are thin curved discs worn directly on the surface of the eye to correct refractive errors or, in some cases, to change the apparent colour of the eye. This page gives a general overview of the main types available and the basic care principles involved. It is not a substitute for a fitting and assessment by a qualified optometrist.

Materials: soft versus rigid

Contact lenses are generally grouped into two broad material categories.

Soft lenses are made from flexible, water-containing plastics called hydrogels or silicone hydrogels. They are the most commonly prescribed type because they tend to be comfortable from the first wear and conform easily to the shape of the eye.
Rigid gas-permeable (RGP) lenses are made from firmer plastics that allow oxygen to pass through to the cornea. They hold their shape more precisely than soft lenses, which can give sharper vision for certain prescriptions, particularly higher levels of astigmatism, but they typically require a longer adaptation period.

Replacement schedules

Soft contact lenses are also categorised by how often they are replaced:

Daily disposables, worn once and discarded at the end of the day
Two-weekly or fortnightly lenses, cleaned and stored between wears and replaced on a set schedule
Monthly lenses, following a similar care routine but replaced less frequently

Shorter replacement cycles generally mean less cleaning and lower risk of deposit build-up on the lens surface, while longer cycles usually cost less per lens but require more diligent care.

Specialised designs

Beyond standard single vision soft or rigid lenses, there are several specialised designs:

Toric lenses, designed with different powers in different meridians to correct astigmatism
Multifocal contact lenses, which contain more than one focusing zone to address presbyopia, similar in principle to progressive eyeglass lenses
Coloured or cosmetic lenses, which can be fitted with or without a vision correction component
Orthokeratology lenses, rigid lenses worn overnight that temporarily reshape the cornea to reduce the need for correction during the day

Any of these designs should still be fitted and prescribed by an eye care professional, since an incorrect fit can lead to discomfort, blurred vision, or eye irritation regardless of the lens category.

Basic hygiene and care

Contact lenses sit in direct contact with the eye, which makes hygiene particularly important. General good practice includes:

Washing and drying hands thoroughly before handling lenses
Using only the cleaning and storage solution recommended for your specific lens type, rather than water or saliva
Replacing the lens case regularly and never topping up old solution with fresh solution
Following the replacement schedule prescribed for your lenses, even if they still feel comfortable
Removing lenses and consulting an optometrist promptly if you notice redness, pain, unusual discharge, or a sudden change in vision

Sleeping in lenses that are not specifically designed and approved for overnight wear increases the risk of complications, since it reduces the amount of oxygen reaching the cornea overnight.

Who might consider contact lenses

Contact lenses can be suitable for many people who wear glasses, particularly those who play sport, want an unobstructed field of view, or simply prefer not to wear frames. They are not automatically suitable for everyone, however, as factors such as dry eye, certain eye conditions, or an inability to maintain the required hygiene routine may make glasses a more appropriate choice. An optometrist can assess these factors during a contact lens consultation, which typically includes measuring the curvature of the cornea and checking the health of the eye surface before any lenses are prescribed.

For general background on eyeglass lenses as an alternative or complement to contact lenses, see the companion page on this site.