close
Health

Contact Lenses and Their Different Types

Contact lenses are small, curved plastic discs that fit over the eye’s cornea. They improve how light enters the eye by focusing it on the retina. Contact lenses stick to the thin coating of tears on the cornea due to surface tension.

In addition to vision correction, specifically coloured contacts can be used to modify the colour of the eyes for cosmetic reasons.

Contact lenses provide maximal peripheral vision, which is very important in sports and games. Contact lenses can also be used in correcting eyesight when the power of each eye varies substantially.

Contact lenses can be worn by the majority of people who need vision correction. However, a tiny percentage of people with dry eyes, frequent eye infections, or severe allergies may be unable to wear contact lenses.

Below are some of the types of contact lenses known:

PMMA Lenses

PMMA lenses are rigid contacts constructed of PMMA material. The lenses prevent oxygen from reaching the cornea directly, but tears carry dissolved oxygen to the cornea when the lens moves when the eye blinks. They are incredibly long-lasting and durable. However, they are no longer available on the market.

Gas Permeable Rigid Lenses (semi-hard contact lenses)

Rigid gas permeable lenses are a newer form of rigid plastic lens that allows oxygen to enter the eye straight through the lens. Although less durable than PMMA lenses, these lenses are more comfortable. Some gas-permeable lenses are designed to be worn for lengthy periods of time.

Semi-hard contact lenses require more adjustment than soft lenses but are less prone to deposit build-up. As a result, they provide good vision while lowering the risk of contact lens-related complications such as eye infections.

Soft Contact Lenses

Soft contact lenses contain water, which makes them soft and flexible and allows different levels of oxygen to enter the cornea.

Soft lens materials are now divided into two types: hydrogel and silicone hydrogel. Hydrogel lenses generally have lower oxygen permeability than hard gas-permeable lenses. In terms of oxygen permeability, silicone hydrogel lenses outperform hydrogel lenses, and some are equivalent to rigid gas-permeable lenses. In general, if you wear contact lenses for lengthy periods of time, utilise silicone hydrogel lenses since they are less prone to cause corneal difficulties due to hypoxia (lack of oxygen).

Soft contact lenses are quite popular in Singapore since they are convenient, pleasant, and provide a high degree of convenience. Some soft contact lenses can be worn for more extended periods of time than rigid lenses. However, it is not recommended to wear these lenses overnight as the risk of corneal infections increases.

Disposable Soft Contact Lenses

Because of the added convenience and safety, disposable soft lenses that may be discarded and changed daily, monthly, or fortnightly are gaining favour. In addition, the probability of allergic reactions and deposit development is decreased by replacing the lenses often.