Latest News : An important warning from the British Contact Lens Association.

Contact lenses

Contact lenses are small pieces of complex plastic that are placed directly over the cornea²¹ and can correct myopia, hyperopia, presbyopia and astigmatism.²²

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.²²

Depending on their replacement schedule and lens type, contact lenses fall into several categories:

1. Conventional soft (Hydrophilic) lenses
2. Gas permeable (rigid) contact lenses
3. Disposable lenses
4. Extended wear lenses
5. Combination lenses
6. Ortho-k lenses
7. Special purpose lenses

Conventional soft contact lenses

Soft contact lenses are made specifically to the patient’s prescription. Not all patients can wear disposable lenses and there may be other reasons why a conventional soft contact lens is prescribed. The life of a conventional soft lens is typically one-to-three years.

Gas permeable (rigid) contact lenses

Gas permeable (GP) contact lenses allow more oxygen to transmit into the eye than soft contact lenses. While GP lenses are not as flexible as soft lenses, they contain silicone, which gives them a greater flexibility and significantly more oxygen permeability than traditional hard lenses. ²⁶

GP lenses take a little longer to adapt to, but provide sharper vision correction and are more appropriate than soft lenses for people with conditions such as astigmatism.²⁶  They are also necessary for specific conditions such as the correction of keratoconus or other irregularities of the cornea.

Disposable soft contact lenses

Disposable contact lenses are designed to be worn during the day and replaced on a regular basis, whether daily, weekly or monthly. The replacement schedule of disposable contact lenses depends upon the prescription and the type of material from which the lens is made.²³

Frequent replacement of contact lenses provides greater comfort and reduced risk of infection from the build-up of protein, calcium and lipids that occur naturally in the eye.²⁴

Extended wear (or leave-in) contact lenses

Extended wear contact lenses are usually soft contact lenses which allow more oxygen to reach your cornea. Depending on the type of lens, extended wear contact lenses can be worn without removal for seven-to-30 days.²⁵

Extended wear contact lenses are not re-usable, thereby reducing the risk of infection that occurs with lens cleaning and reuse.²⁵

Combination contact lenses

Combination lenses consist of a rigid centre lens with a surrounding soft skirt. They are normally used in specialist practices mainly for medical purposes such as distorted or damaged corneas.

Ortho-k contact lenses

Ortho-keratology lenses are used to correct the lower levels of myopia by wearing a rigid gas permeable lens overnight. Each lens is designed specifically for an individual cornea and utilises the fluid layer trapped between the lens and eye to remodel the corneal shape.

The lens is removed on waking and gives clear vision over that day, sometimes longer. There is also early evidence that this procedure may slow down the progression of myopia in teenagers. Not all contact lens practitioners do ortho-k work and you should discuss the pros and cons of this with your own practitioner.

For more information on ortho-k lenses visit www.osa.net.au.

Other specialist contact lenses

Many other specialist lenses are available that may be used in more unusual or difficult cases. Speak to your optometrist or ophthalmologist for assistance.

Contact lens hygiene fundamentals

Follow these guidelines for good contact lens care to protect the safety and health of your eyes.²⁸

1. Before handling a contact lens it is important to wash your hands with warm water and soap. Dry your hands with a clean towel.
2. Any time a lens is removed from the eye, it should be properly disinfected.
3. Safety is enhanced significantly by rubbing and rinsing contact lenses both prior to and following storage.
4. Use the lens solution provided specifically for your contact lenses and rub the lens between the palm of one hand and a finger for five seconds on each side.
5. Rinse the lens thoroughly with sterile solution. Never use tap water to rinse or store your contact lenses. Water is a common source of very infectious and potentially damaging micro-organisms that can produce sight threatening infections.
6. Wear your contact lenses as prescribed. Your eye care practitioner will recommend a wearing schedule specific to the type of contact lenses you have selected. Only wear your contact lenses for the time recommended.
7. Place the clean lens in your container and fill the container with the fresh disinfectant solution provided for your lenses. Do not re-use solution in the case or top-up with solution. Replace your lens case frequently, every time you open a new bottle of solution.
8. Clean your lens case after each use with sterile solution and allow to air dry.
9. Always read the directions provided for the use and care of your contact lenses and use the appropriate solutions as recommended by your eye care practitioner.
10. When contact lenses have been stored for more than seven days, regardless of whether peroxide or multi-purpose solutions are used, lenses should be effectively re-disinfected before the next use.
11. If irritation or infection occurs (signs include redness, burning, or excessive tearing) remove your contact lenses immediately and discontinue wearing until you see your eye care practitioner.
12. Never wear another person’s contact lenses, especially if they have been worn before. Using other people’s contact lenses may spread infection.
13. Call your eye care practitioner immediately if you have any questions or concerns.

We are pleased to be able to provide care and handling instructions for soft and RGP Lenses courtesy of Elsevier Ltd.
 
For soft contact lens wearers please click here.
For rigid contact lens wearers please click here.

References

21. Roat, M. 2003, Refractive Disorders in The Merck Manual of Medical Information, 2nd Edition, West Point, PA, USA, p. 1286-1290.
22. Segre, L. 2008, Contact lens Basics, Access Media Group. Accessed 5th February 2009.
23. Segre, L. 2007, Disposable Contacts: A Healthy Choice, Access Media Group. Accessed 5th February 2009.
24. Optometrists’ Association Australia 2009, Lens Care. Accessed 5th February 2009.
25. Segre, L. & Del Pizzo, N. 2008, Extended Wear Contact Lenses, Access Media Group. Accessed 5th February 2009.
26. Del Pizzo, N. 2008, Gas Permeable (GP) Contact Lenses, Access Media Group. Accessed 5th February 2009.
27. White, G. 2007, Caring for Soft Contact Lenses, Access Media Group. Accessed 5th February 2009.
28. Institute of Eye Research Guidelines for the safe and effective use of contact lenses, AMO Asia Ltd. Accessed 19th February 2009.