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Information on Contact Lenses

There are two main types of contact lenses - soft and rigid gas permeable (RGP). All contact lenses require a valid prescription and fitting by a contact lens professional (optometrist or contact lens optician).

Soft Contact Lenses

Soft contact lenses are made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses are easier to adjust to and are more comfortable initially than rigid gas permeable lenses. Because they take little getting used to, it can be easy for people to combine spectacle and contact lens wear - for example wearing lenses for social or sporting occasions and glasses the rest of the time.

Newer soft lens materials include silicone hydrogels which allow significantly more oxygen to your eye during wear. This tends to reduce the chances of adverse effects relating to lens wear.

Planned replacement of soft lenses

The majority of soft contact lenses nowadays are supplied on some form of pre-planned replacement schedule. Daily disposable lenses are worn once and discarded, with a brand new pair of lenses used each time lenses are worn. This is a very safe and convenient way to wear contact lenses but is not suitable for everyone.

Many soft contact lenses are supplied for frequent or planned replacement. These lenses will be worn for a pre-determined period, usually either two weeks or a month, removed at the end of each day, cleaned and then stored overnight before the next day's wear. This form of lens wear suits people who need more complex lenses that may not be available as daily disposables, or who wish to minimise the cost of their lenses.

Rigid Gas Permeable (RGP) Contact Lenses

Rigid gas permeable contact lenses (RGPs) are more durable and resistant to build up of deposits, and generally give clearer, crisper vision. They tend to be less expensive over the life of the lens since they last much longer than soft contact lenses (1-2 years). They are easier to handle and less likely to be damaged. The RGP materials we use allow more oxygen to the eye than conventional soft lenses, and so may be the more healthy option for those wanting to wear lenses for most of the day, every day of the week. They also may be the easiest and most cost-effective way of correcting certain prescriptions, for example, astigmatism. They are not as comfortable initially as soft lenses, however, and it may take a few days or weeks to get used to wearing RGPs.

Extended or Continuous Wear Contact Lenses

Extended wear contact lenses are available for overnight or continuous wear, ranging from one to six nights or up to 30 days. Extended wear contact lenses are usually silicone hydrogel soft contact lenses. There are also some RGP lenses that are designed and approved for overnight wear. The length of continuous wear (6-30 nights) depends on lens type and your eye care professional's evaluation of your tolerance to overnight lens wear.

The risk of adverse effects related to lens wear are greater for extended wear. The Eye Clinic does not currently supply contact lenses for overnight wear.

Decorative (Plano) Contact Lenses

The Eye Clinic offers a range of coloured lenses both with and without refractive correction. We can also fit custom hand-painted cosmetic lenses, designed to hide an unsightly eye due to injury, for example.

Some contact lenses do not correct vision and are worn solely to change the appearance of the eye, usually by changing eye colour. Even though these decorative lenses don't correct vision, their sale is limited by the law to registered practitioners, just like contact lenses to correct vision. This is because they carry the same risks to the eye. People without valid prescriptions have bought decorative plano contact lenses from a variety of unregistered and unlicensed retailers. This is not recommended - buying contact lenses without a prescription can be dangerous.


Specially-designed RGP lenses are fitted to be worn overnight to change the shape of the eye to correct low levels of short-sight (myopia). Once the eyes have adapted to wearing the lenses, the wearer should be able to wear them at night only and see clearly throughout the day without wearing any spectacles or contact lenses. Orthokeratology fitting is undertaken within a specialist research clinic within the Bradford School of Optometry and Vision Science. For further information, please contact Ms Annette Parkinson.

What type of lens should I wear?

It can be quite complicated making the correct decision about which lens type would suit you best. We advise that you book in for a contact lens trial with an open mind. We will measure your eyes, look at your prescription and then discuss with you the way you would prefer to wear lenses, before making any recommendations about which lens type would be best for you.

For further information on contact lenses, visit the British Contact Lens Association.

Risks of contact lens wear

There are some slight risks associated with contact lens wear. These can be reduced by following carefully the instructions you are given when you start wearing lenses. The most serious potential complication is a sight-threatening eye infection and the chance of that varies with lens type. For daily wear of RGP lenses this is about one in 20,000 wearers; for daily wear of silicone hydrogels the risk is similar and for daily wear of soft lenses the risk is about one in 2,500.

Most of the people who have problems have either worn their lenses for longer than was advised, have not replaced them as often as advised or have not cleaned and looked after them correctly. If these simple precautions are followed then contact lens wear is usually very safe.