Beauty of the Eye

Contact lenses are used almost by everyone today be it to correct the eye vision or just to enhance or change their eye color. Many people prefer contact over glasses for the cosmetic reason and for the freedom it provides. Contact lenses mainly compose of hard lenses and soft lenses. Nevertheless many people regard contact as just a piece of plastic but little do they know what materials are used to produce it.

The main components for the production of contact lenses are polymer. Hard contact lenses are made from some variant polymer of polymethyl methacrylate (PMMA). Polymethyl methacrylate (PMMA) is a clear, colorless polymer which is widely used in the optical industry. The disadvantages of using polymethyl methacrylate are low impact strength and poor chemical resistance. The advantage of using polymethyl methacrylate is due to the clarity and UV resistance.

polymethyl methacrylate (PMMA)

polymethyl methacrylate (PMMA)

Chemical equation

Methyl Metacrylate

Polymethyl methacrylate

PMMA is also often used as an alternative to glass and in competition with polycarbonate. It is often preferred for its moderate properties, easy handling and low cost. It is often used as lenses, light covers, glazing (particularly in aircraft), light pipes, meter covers, bathroom fittings, outdoor signs, skylights, baths, and toys. Acrylic film is laminated over ABS sheet to provide UV protection.

Soft lenses are made from poly hydroxyethyl methacrylate. Poly hydroxyethyl methacrylate (pHEMA) are used mainly because it has hydrophilic properties that is it can soak up water and retain its shape and optic functions. Poly(2-hydroxyethyl methacrylate) (pHEMA) is used because in water, the polar hydroxyethyl side turns outward and the material becomes flexible making it suitable for the production of contact lens when used with side polymers.

Poly hydroxtethyle methacrylate

In the future, contact lenses will be made from a new substance that is currently being researched called siloxane which is a silicon-oxygen compound. Siloxane forms a thin, flexible film and admits oxygen through to the eye 25 times better than current standard soft lenses. However the disadvantage of siloxane is that it does not wet easily and attracts lipids to its surface causing it to cloud.

Siloxane

Reseachers have found a way to add flourine molecules to the siloxane compound causing the molecule to resist lipids. Wetting agents are also added into the siloxane which changes its molecular shaped when boiled in saline solution so the material will soak up water like the traditional soft lenses.

Contact lenses

As people say, beauty is in the eye of the beholder. In this case, its the holder's eye that holds the beauty.