Modern contact lenses.

Modern contact lenses.

The modern contact lens actually has its beginning round the turn of the 20th century.

Adolf Fick gets the credit for inventing the 1st practical pair in 1887. But, it was Carl Zeiss, the famed lensmaker, who developed a glass contact lens that fit over the cornea that formed the prototype for all later work. It was still to be many decades before Touhy invented the 1st plastic corneal lens, using Plexiglas as a material. Whilst work commenced in 1952, it wasn't till 1971 the modern hydrophilic soft contact lenses came on the market. That word, 'hydrophilic' ( meaning 'water loving' ), is the key to fresh contact lenses.

Today's lenses are made from a plastic polymer ( pHEMA ) that allows the contact lens to absorb water. Some lenses were formed in a molding process called spin-casting, where the plastic is spun into the required shape. Early techniques needed last shaping with a lathe, but today the method is so correct the lenses can be made wholly thru molding alone. The lathe process may still be employed in some areas of the Earth, though, particularly for hard contact lenses that still make up anywhere up to 25% of those sold. In this strategy a tiny circle called a blank is cut from a plastic rod and fastened onto a lathe with wax. That is carried out by polishing the result into actual curves on both sides of the lens. Today, a P. C. Controls the method, which is kept correct by being fed info from the individual patient using data gathered during the eye exam. The lens is then sterilised, regularly by being boiled in salt water for many hours, which also softens it. They are then packed in a glass vial containing a sterile saline ( salt water ) solution.

As the lens material is hydrophilic it soaks up a lot of the solution, making it up to 75% water in the final analysis. As the solution is analogous to human tears that moisturize the eye, the contact feels good and works well during use. Research continues into finding materials that are longer lasting, more comfortable and safer to use.

Some comparatively fresh advances, as an example, include the Stiff Gas Permeable lens ( RGP ) invented in 1979, but marketed much later. That makes them more snug and safer to use over the long run. Several can now be worn steadily for so long as a week to a month. On the leading edge are new implantable contact lenses that are essentially placed into the eye and never need changing or cleaning.