Types of contact lenses
Before you read this text you have to understand that you mustn’t choose yourself lenses, only grounding on the information which were written. This text has only informational purpose.
Compared to glasses, contact lenses are a relatively modern invention. The first mention of the contact lenses was found in Italy. Historians claim that Leonardo Da Vinci about in 1508, was on its historical beginning. The next moment when contact lenses were mentioned was 350 years afterwards. In 1827, was English astronomer Sir John Herschel. He proposed the idea of making a mold of a person's eyes. From that moment scientist form the all over the world became to investigate and gave new ideas of making the lenses better. During investigation of the contact lenses were invented different types of lenses, about which you’ll read in the following text.
If you use contact lenses, probably you’re faced with a problem of losing your natural vision.
Don’t matter how long you use lenses and whether you wear them at all, you want to get know something about types of contact lenses. Now you will find out the basic information about the types of lenses and their differences. Let’s go.
There are different types of contact lenses. In general, contact lenses can be categorized into two types, based on how long they are approved to be worn before being removed. First of all, you should know that people use lenses as for solving their vision problems and for style (for example, to change the pupil color for adding some mystery). So generally, lenses are divided to the lenses for vision correction and cosmetic.
Let’s look at the cosmetic lenses. In the most such kind of lenses people use to change the eyes color. But also, these lenses could be used to hide an albugo and correct the refraction problems. Such lenses type is rated for one year of use.
So, you already got knew about cosmetical lenses, now you will find out about medical lenses and the first lenses you’ll get know would be bifocal contact lenses. That lenses type is multipurpose. You can say: “Multipurpose lenses? How could it be? Do these lenses help people with myopia (you can’t see far but you able to see around) and hyperopia (other way round)?” You’re right! It means, without any discomfort you can see far and around without falling back on some vision gadgets. Such kind of lenses are obsolete, so people invented multifocal lenses.
Next type of contact lenses are soft lenses. They are much comfortable than rigid lenses. They are made of hydrogel and it means they can be rolled or slightly folded without damaging the lens. They don’t have an adaptation period as the rigid ones. So, as these lenses type are made of hydrogel, they got some specific disadvantages: they are slightly stiffer and the lens surface can be hydrophobic, thus less "wettable" – factors that can influence comfort of lens use.
Conventional contact lenses
Next contact lenses type is conventional contact lenses. They’re made of a fairly stiff plastic (polymethyl methacrylate, or PMMA). It does not mold to the shape of the eye. They’re inexpensive and durable. Because of it it’s the least comfortable type of contact lenses. So as they reduce the amount of oxygen that reaches the pupil, people who use them are at risk of getting an overwearing syndrome or some other problems.
The two following types of contact lenses are almost the same, but they got some differences.
Usually, they’re called extended wear contact lenses (EW contact lenses).
There are long term contact lenses and long wear contact lenses. They’re thinner than regular daily wear soft lenses and because of it these lenses deliver more oxygen to the cornea. Almost all EW lenses are approved for continuous wear up to seven days, but depending on the doctor recommendations some lenses of this type cold be worn during thirty days of continuous wear.
The last info you’ll get know about types of hard contact lenses. They are also categorized to the several types. There are:
- Rigid gas-permeable (RGP) lenses
- Polymethyl methacrylate (PMMA) lenses
RGP lenses are the most common type. They’re made of a flexible plastic material that typically includes silicone. This lightweight material allows oxygen to pass directly through the lens to reach the cornea. These lenses are larger than PMMA lenses, and cover more of your eye. Also, the edges of RGP lenses fit more snugly against the surface of your eye. This makes them more comfortable to wear compared to the older variety. It also allows the lenses to stay on your eyes more securely.
PMMA lenses are less common, comparing to RGP lenses. Earlier types of polymethyl methacrylate (PMMA) lenses were harmful for wearing. But today PMMA lenses are seldom prescribed. PMMA lenses did not allow oxygen to pass through the lens. The only way oxygen could reach the cornea was for tears to wash under the lens each time you blinked. To allow tears to move under the lens, PMMA lenses were fairly small in size. Plus, there had to be a gap between the lens and the cornea. Because of it PMMA lenses are uncomfortable to wear. They can easily pop out, especially when playing sports.
But what about the best type of contact lenses? You just read the information about different types of contact lenses, you got know about some differences of the lenses which probably you thought they’re the same type. As were written at the text beginning, you mustn’t choose yourself lenses, only grounding on the information which were written, because this text has only informational purpose.