Contact lenses are an alternative to glasses for those with short sightedness, long sightedness, astigmatism and presbyopia.
Types of contact lenses
There are 2 main types of contact lenses:
- Rigid gas permeable lenses
- Soft contact lenses
Soft contact lenses are used by 90% of contact lens wearers. There are 2 main kinds:
- silicone hydrogels
Silicone hydrogels are the newer generation and have a lower water content than hydrogels. There are at least 15 different silicone hydrogel materials with newer materials having higher water content and being more flexible to try and improve comfort. In general, they have a higher oxygen permeability than hydrogels. They were initially conceived as extended wear contact lenses but even daily disposable versions are available now.
In general, the comfort of hydrogels and sillicone hydrogels is similar although studies may be conflicting. Hydrogels tend to accumulate proteins and silicone hydrogels lipids. Good contact lens care regimes are equally important for both.
Soft contact lenses come in daily, bi weekly and monthly disposable versions. Conventional soft contact lenses can be used for 1 year or so before replacement. The disposable versions are meant to reduce the inconvenience of contact lens care regimes. Daily disposables require no cleaning and are disposed off after a single use. However, the on going cost will be higher for the convenience.
Rigid gas permeable lenses have high oxygen permeability, easier maintenance, excellent vision and safety. The main drawback is short term discomfort in the new user which may take 3 months to adjust to. Over the medium and longer term though, comfort levels are comparable to soft lenses. They are a good choice for those who develop allergy to soft contact lenses and who still want to continue wearing contact lenses.
Newer uses of contact lenses include cosmetic uses like changing the colour of the eye , making the eye more prominent and some contact lenses have graphics printed on them.