Soft contact lenses/most commonly used lenses are made from soft, flexible plastics, known as hydrogels, which contain water. The water allows oxygen to pass through the lens to the eye. This is important, as
the cornea (the clear front surface of the eye) obtains its oxygen supply directly from the air.
Most soft contact lens wearers find that they adapt to the lenses quickly and they are comfortable straight away (unlike rigid lenses, which require some
adaptation). This makes soft lenses suitable for people who do not want to wear their lenses every day, such as a footballer or netballer who only wears their lenses when they are playing.
Soft lenses are particularly suitable for sports, as they are
difficult to accidentally dislodge. Soft lenses are suitable for correcting most refractive errors. Special “toric” lenses can be used to correct astigmatism.
Hard lenses are made from plastics that are
less flexible than those used for soft lenses. Materials today allow almost as much oxygen to reach the eye as if no lens was being worn.
Rigid lenses provide better vision than soft lenses, as the optics can be better controlled, and are suitable
for a wider range of refractive errors. In some conditions in which the front surface of the eye becomes distorted, such as keratoconus, hard lenses are the only way of satisfactorily correcting vision.
Hard lenses require some adaptation on the part
of the wearer. Typically they are less comfortable than soft lenses for the first week or two of wear, but after that they do not cause any discomfort. Adapting to hard lenses is a bit like breaking in a new pair of shoes.
Rigid lenses are more durable
than soft lenses, so they do not need to be replaced as often.
Daily wear Only Lens
The most common wearing schedule is “daily wear”, where the lenses are inserted in the morning, worn through the day, and taken out
at night. The lenses are then cleaned and disinfected before being worn again.
24 hour x 30 Day/Extended wear Lens
Some newer lens types allow wearers to sleep in their contact lenses, either occasionally, or for up to 30 days.
You should NEVER sleep in your contact lenses unless your optometrist has specifically advised you that you can do so. Sleeping in the wrong type of lenses can cut off your corneas’ oxygen supply while you are asleep, causing severe inflammation and
possibly permanent damage.
Rigid lenses are typically replaced every one to two years. Often the replacement is necessary because the wearer’s prescription has changed or the lenses are scratched.
Most soft contact lenses these days are intended to be replaced at shorter intervals, typically from one day to 4 weeks. This ensures that the lenses are always clean, as they are replaced before any deposits can build up on them.
The frequent replacement of lenses especially One Day/Use lenses have reduced infection Rates.