Contact LensesDid you know contacts lenses are made out of plastic? Well they are! You don't really think about it when you wear them, but its a small plastic disk floating on your eyeball. Contacts are mostly used for correcting vision, but they are also used for cosmetic reasons such as hiding disfigurations in eyes or to change the color of an iris. You probably didn't know this, but contacts are also used for medical purposes, like treating or studying eye diseases, or to measure the electrical output of an eye.
The picture below is a diagram of how the lens rests on the eye.Do you know what kind of contacts you wear?Well there are two kinds of lenses, there are soft lenses and hard lenses. The two lenses each correct certain things in the eye. For example soft lenses can correct mild to moderate astigmatism, but not severe astigmatism. Hard lenses are the ones that correct severe astigmatism. Soft lenses can also be bifocals, for those who need near and far sight correction.
The video below thoroughly explains how contacts are made.Here is some interesting history about contacts!- In 1888 the first contact lenses were made, but they were made out of glass- In the 1940's plastic lenses were introduced - They used to prevent tears from moving on the eye ball - Scleral lenses are rarely used today, except in a case where the eye ball and eye lid don't need to touch - In the 1940's lenses that float on the layer of tears in the eye were introduced, and called Corneal lenses - In the 1970's lenses were made thinner and softer | Glass LensesWe all know glasses are for people with vision defects. But did you know only a thin layer of glass or plastic can fix it all. You probably also didn't know that about 62% of people wear glasses or contacts. That means about 38% of people have perfect vision, or don't know they need glasses. Lots of people don't like wearing glasses or contacts, but they don't realize they are missing everything they NEED to see in the world.
The video below describes how glasses are made.Are your glasses lenses concave or convex or cylindrical?There are three types of lenses for glasses. Concave, Convex and Cylindrical. If you are nearsighted your lenses would be concave. If you are farsighted your lenses would be Convex. If you have astigmatism your lenses would be Cylindrical, but if you have astigmatism combined with farsightedness or nearsightedness, your lenses would be either Concave or Convex.
The picture in the link is a diagram showing the three types of lenses.Click here, for the picture!
A little history on glasses- Benjamin Franklin made the first bifocals in 1780
- Glasses made for faulty vision were made in Pisa, Italy in 1286 - The idea of glasses spreaded quickly to China - Glasses became popular in the 15th century - Convex lenses were used first, concave lenses didn't come until the 16th century |