Although there is a huge selection of contact lenses available, there is no need to be daunted by the choice. Contact lenses can be divided into several groups based on what they're made of, how often you need to replace them, whether you can sleep in them and what eye condition they are correcting.
Your lens choice depends on four factors which, in the jargon are: ‘material, function, modality and replacement schedule’.
Soft Contact Lenses: Contain from 25% to 80% water, are easy to get used to and are very comfortable.
Silicone Hydrogel (SiHy): The latest soft contact lens material which can deliver significantly more oxygen to your eye than conventional soft lenses, which is much healthier and more comfortable.
Rigid Gas Permeable (GP): These lenses take longer to adapt to, but are more durable and more resistant to deposit build-up; they can also provide clearer vision for some people with higher prescriptions.
Spherical (standard) lenses: correct single-vision prescriptions with little or no astigmatism.
Toric lenses: correct single-vision prescriptions with significant astigmatism.
Multifocal lenses: correct both reading and distance prescriptions in a single lens, just like bifocal or varifocal glasses. For low reading powers, spherical lenses can also be worn with one lens for distance and one for reading; this is known as monocular vision.
Coloured lenses: change the apparent colour of the eye, with or without vision correction.
Day-time-only, in solution at night: Many soft lenses and traditional GP lenses are worn only during the day and are taken out and kept in solution at night.
Day-time-only and then throw away: Daily disposable contact lenses are worn just once for a day and then thrown away, eliminating the inconvenience of solutions.
Extended (Overnight) Wear: Most SiHy lenses, and some others, are approved for extended wear, allowing you to sleep in them; some for up to 30 continuous days and nights – the ultimate hassle free contact lenses!
Night-time wear: The revolutionary Ortho-K lenses are special GP lenses that you wear only at night. You put them in just before bed and take them out first thing in the morning -- your vision is corrected and you can see unaided during the day!
Daily Disposables: Thrown away every night. Packaged in 30s or 90s (one or three months supply).
Other Disposables: Thrown away every week, fortnight or month as specified and packaged in 3s, 6s or 12s (six weeks to six months supply). Some lenses can be worn either as day-time-only or extended wear (with different replacement schedules for each modality).
Traditional Soft lenses: Usually changed every year.
GP lenses: Usually changed every two years or so, because they are made of a very durable material (although a specification change might require sooner replacement).
