Contact lenses consist of specially manufactured complex polymers that are placed directly over the cornea and can correct myopia, hyperopia, presbyopia, astigmatism, aphakia, keratoconus and other irregular or scarred eyes…
Contact lens wear schedules include daily wear, designed to be worn during the day and taken out at night, or extended wear, which can be worn overnight.
What Are The Different Types of Contact Lenses?
There are several different types of contact lenses available today. Your optometrist will be able to advise you on the type of contacts best suited to you. A list of CCLSA optometrists is provided here.
Please remember that professional advice from an optometrist is required to determine the contact lenses prescription. This includes the lens type, material, size, curvature and power. Your optometrist will also give you professional advice on contact lens care and maintenance to ensure your eyes stay healthy and seeing well. It is a requirement in Australia that all contact lenses supplied have a valid contact lens prescription written by an optometrist.
The main types of contact lenses available today are:
- Disposable soft lenses
- High oxygen (silicon hydrogel) disposable soft lenses
- Extended wear soft lenses
- Multifocal soft lenses
- Conventional soft lenses
- Rigid gas permeable lenses
- Ortho-k lenses
- Scleral or mini-scleral lenses
- Hybrid lenses
- Cosmetic or coloured lenses
- Bandage contact lenses
- Special purpose lenses
Disposable soft lenses
The vast majority of contact lenses worn around the world today are soft disposable lenses. These lenses are made of soft, flexible plastics known as hydrogels or, in more recent years, silicon hydrogels. Disposable contact lenses are available to suit most prescriptions and are generally very comfortable with no or minimal adaptation required. Disposable contact lenses are available in daily, two weekly and monthly designs and are replaced at these intervals. Daily disposable contact lenses wearers benefit from a fresh pair of lenses every time they wear the contacts, generally providing excellent comfort and eye health. These lenses require no cleaning or maintenance due to their daily replacement.
Two weekly or monthly disposable contacts are also available in a wide range of prescriptions and contact lens materials. These lenses require minimal maintenance; your optometrist will advise you of how to best care for your lenses.
Extended wear contact lenses
Extended wear contact lenses are lenses that you can sleep in, for up to 30 nights at a time. Extended wear offers lifestyle benefits and the convenience of not having to remember to take to contacts out before sleeping. High oxygen silicon hydrogel lenses are used for extended wear, allowing for greater flow of oxygen to the eye. Not all contact lenses are suitable for extended wear and extended wear is not suitable for all people. Extended wear carries a greater risk of infection and other complications compared to wearing contacts on a daily wear basis, so it is important that professional advice from an optometrist is provided and regular checks with your optometrist are conducted to monitor eye health.
Extended wear lenses are also used in cases where inserting and removing the lenses can be difficult, such as aphakia in infants (where congenital cataracts are removed and no intra-ocular lens is implanted) or in adults who have difficulty handling the contact lenses.
High oxygen (silicon hydrogel) disposable soft lenses
In recent years there have been many advances in the development of contact lenses. At the forefront of these developments has been the advent of silicon hydrogel disposable contact lenses. Silicon hydrogel lenses allow better oxygen permeability or breathability compared to regular hydrogel contact lenses. This has long term health benefits for the eyes, allowing for longer wearing times and helping to keep your eyes white and healthy.
Since the initial launch of silicon hydrogel disposable contact lenses in 2002 the technology has been continually refined resulting in softer, more comfortable lenses. The range of prescriptions available in these materials is also continually expanding. Silicon hydrogel lenses are available in several different lens materials and designs, including daily disposable, two week or monthly disposable and multifocal lenses.
Silicon hydrogel lenses may be suitable for you to sleep in, allowing greater flexibility and lifestyle benefits (see extended wear contact lenses, below). It is particularly important that if you wish to sleep in contact lenses this is discussed with your optometrist and that the health of your eyes is regularly checked.
Multifocal contact lenses
There have been many advances in multifocal contact lens design in recent years in what is a rapidly expanding area. Multifocal contact lenses combine distance and near vision for people aged 40 plus who are presbyopic (a normal age-related condition where the lens loses its ability to focus on close objects). Multifocal contact lenses are available in several different disposable and high oxygen silicon hydrogel materials, including daily disposable lenses. Vision with multifocal contact lenses has the advantage of not being dependent on head position as with multifocal glasses and incremental changes in presbyopia are more easily accounted for compared to laser surgery.
Conventional soft contact lenses
Conventional soft contact lenses are soft hydrogel lenses that are typically replaced every 12 to 18 months. As the range of prescriptions available in soft disposable contact lenses has expanded, conventional soft lenses are used less and less as soft disposable contact lenses generally offer eye health, comfort and convenience benefits compared to conventional soft lenses. However, for certain prescriptions, conventional soft contact lenses may still be the lens of first choice.
Rigid gas permeable contact lenses
Rigid gas permeable (RGP or GP lenses) are made from hard, durable plastics that transmit oxygen.
RGP lenses take a little longer to adapt to compared to soft lenses. They offer excellent optics, particularly for astigmatic (oval-shaped) or irregular corneas. They are particularly good lenses for conditions such as keratoconus and for post-corneal graft lens fitting.
Ortho-k contact lenses
Ortho-k or orthokeratology lenses are rigid gas permeable lenses that are worn overnight to correct mild to moderate short-sightedness and mild astigmatism. These lenses reshape the cornea or front surface of the eye and are taken out on waking, allowing people to be free of optical correction during the day.
There is some evidence that ortho-k can reduce the progression of short-sightedness. For this reason, ortho-k is gaining some popularity in use with children who are shortsighted. There is a great deal of current research in this developing area. More information on ortho-k can be found at www.osa.net.au.
Your optometrist will be able to provide professional advice as to whether ortho-k is suitable for you and to discuss the pros and cons of this method.
Scleral or mini-scleral lenses
Scleral or mini-scleral lenses are special purpose rigid gas permeable lenses. These lenses are larger than standard RGP lenses with the edge of the lens resting on the peripheral cornea or sclera (the white part of the eye). Scleral or mini-scleral lenses have had somewhat of a revival of late. They are used primarily for eyes with irregular corneas such as in keratoconus or pellucid marginal degeneration. Their larger diameter can result in better comfort than small diameter RGP lenses. As they hold a reservoir of fluid behind the lens, they can also be used to help people with severe dry eye disease, such as in Sjögren’s syndrome, Steven’s Johnson syndrome or neurotrophic corneal disease.
Hybrid contact lenses
Hybrid lenses consist of a rigid gas permeable lens in the centre with a soft lens skirt surrounding the central zone. They aim to provide the excellent optics of RGP lenses with the improved comfort or easier adaptation of a soft lens. They are used primarily for conditions such as keratoconus where the corneal shape is irregular.
Cosmetic or coloured lenses
Coloured contact lenses are available to change or enhance the colour of your eyes. These are available for dark and light coloured eyes in a range of colours. They are available with or without optical correction. You can even get novelty contact lenses with crazy designs if that is what you are after. Coloured contact lenses are available in daily, monthly disposable and soft conventional designs. It is important to remember that even coloured contact lenses without optical correction should be fitted by an optometrist, as professional advice regarding eye health is essential.
Bandage contact lenses
Contact lenses can also be used in certain cases where damage to the cornea or front surface of the eye causes pain. High oxygen silicon hydrogel disposable contact lenses are generally used here and can help the cornea to heal as well as significantly reducing eye pain. Bandage contact lenses may be used in conditions such as recurrent corneal erosion, corneal abrasion or bullous keratopathy.
Special purpose lenses
Other special purpose lenses are available that may be used in more unusual or difficult cases. Your optometrist will be able to give you advice specific to your needs.
You can find some good guidelines on contact lens care here
A Few Supporting References
- A brief history of contact lenses
- Van Der Worp, E. A guide to scleral lens fitting. Scleral Lens Education Society; 2010.
- Roat, M. 2003, Refractive Disorders in The Merck Manual of Medical Information, 2nd Edition, West Point, PA, USA, p. 1286-1290
- Segre, L. 2008, Contact lens Basics, Access Media Group
- Segre, L. 2007, Disposable Contacts: A Healthy Choice, Access Media Group
- Optometrists’ Association Australia 2009, Lens Care.
- Segre, L. & Del Pizzo, N. 2008, Extended Wear Contact Lenses, Access Media Group
- Del Pizzo, N. 2008, Gas Permeable (GP) Contact Lenses, Access Media Group
- White, G. 2007, Caring for Soft Contact Lenses, Access Media Group