What are the Contact Lenses?
The first contact lenses to be used as an eye aid were made by A.E. Fick in 1887. These early lenses were first made by blowing the glasses and then by grinding and polishing bottoms of glass test tubes. These lenses were not successful and for a long time remained just a subject of academic study. After 1950 smaller lenses were used that covered only the cornea which is the front surface of the eye and floated on a layer of tears. Such lenses are usually 7 to 11 millimeters in diameter and .1 to 1mm in thickness and can be worm all day without removing. The contact lenses are woen directly on the cornea of the eyes to correct any defects of vision. All the defects that are corrected by regular eye glasses or others that cannot be corrected thus can be rectified by contact lenses.
To fit the contact lenses the eyes are first tested for the vision defects just as they would be in case of spectacles. Then the radius of curvature of the eye surface is found out by using a device called keratometer. After deciding the diametre and power of the lens the prescription goes to the manufacturer for making the lens. To make the contact lens the plastic rod is first sawn into sections and then turned on a lathe to make button shaped tablets known as bonnets. Then they are given the right curvature with the help of machines for obtaining the desired power and then polished finally. The lenses are then examined to see whether they fit the eye well or not. Finally they are worn on the cornea. With increasing acquaintance these lenses can be worn comfortably by most people for 12 hours at a stretch. They are more useful in active sports since they are not easily lost or broken and can even be tinted to protect against the sun. They are also expensive and some people find difficulty in wearing them. Soft lenses of hydroxyethyle are used in modern contact lenses.