Soft contact lenses

Classic contact lens types: hydrogel silicone hydrogel hybrid (RGP – Rigid Gas Permeable part in the middle of the lens, edges are out of soft materials) Since 1999, some types of silicone hydrogel contact lenses with high oxygen permeability have been approved for extended wear (to be worn overnight, or for longer than one day). Nowadays, extended wear is not often recommended, as prolonged wear presents a higher risk of eye infections and other health complications.

Advantages

The advantages of soft contact lenses include comfort of wear, easy application and low cost. Silicone hydrogel contact lenses have a high oxygen permeability, which ensures sufficient oxygen flow to the cornea. On the other hand they have worse wettability, increased stiffness and a propensity for harboring lipid deposits when compared to hydrogel lenses.

Disadvantages

Soft contact lenses are made of a more fragile material, which makes them more difficult to care for. They must be cleaned or changed regularly in order to prevent lipids, proteins and other deposits from forming on the tear film. Complications can occur due to insufficient lens care, incorrect selection of lenses, or by wearing the lenses longer than prescribed. Neglecting the lens care can lead to conjunctivitis and corneal neovasculariza­tion.

Replacement schedule

Each type of contact lens is designed to follow a specific replacement schedule, ie. how often the lenses must be disposed of and replaced.

Daily wear routine

The lenses should be worn for no more than 16 hours a day (for some brands, this time should be limited to 10 hours because of their lower oxygen permeability). The daily wear routine starts in the morning when the lens is inserted into the eye. At night, the lenses should be removed and placed in a lens case with contact lens solution where they will be disinfected overnight.

Extended wear

Extended wear is possible with several types of daily contact lenses that have high oxygen permeability. Contact lenses with extended wear can be worn overnight, but for a maximum of 6 days continously. This type of wear shortens the total lifetime of the lenses. (Eg. Monthly lenses will be viable for three weeks instead of four.)

Continuous wear

Contact lenses for continuous wear can be worn without removing for the duration of the time for which they are prescribed. For example, monthly lenses can be worn for 30 days, 24/7. This type of wear should only be prescribed by an eye specialist, because it is not suitable for every eye.

Lifetime of soft contact lenses

Daily contact lenses – inserted in the morning; thrown out at the end of the day Bi-weekly and monthly contact lenses – removed each night to be disinfected with contact lens solution Quarterly or Yearly contact lenses – not often used now due to the lower prices of the types above.

Durability of contact lenses

Contact lenses gradually accumulate lipid, protein, and calcium deposits in which microorganisms can grow. Therefore, it is necessary to properly clean the lenses with a suitable solution. This helps to remove impurities and properly disinfect the lenses.

Summary

Soft contact lenses have one disadvantage – they are more prone to accumulation of impurities. Therefore, they must be changed regularly to avoid possible eye infections. The advantage of these lenses is that they have high oxygen permeability, so they can be worn for a longer time. Some can even be worn continuously.
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