0 Contact Lenses

Introduction:
The contact lenses are used for correcting the eyes view (which is disturbed due to refractive error). Because the beauty of the man is depended on its eyes so he/she will never want to cover its eyes with glasses in case of any eye problem e.g. eye weakness.
In such cases the special type of the thin plastic made discs are being putted to the eyes which get fix to the eyes (due the friction of the tears in the eyes and them).The contact lenses gives the better vision as compared to the eyeglasses.
History:

1. Contact lenses were firstly described by the Leonardo da Vinci  in the beginning of the 1500s.     
2. In 1801 Thomas Young used contact lenses in a microscope 
3. In 1888 two European suggested contact lenses for correcting the view of the eyes.
4. In 1929 a greatest scientist Dr. Joseph Dallos introduced the method of measuring the size of the human eye helped in making the lenses of the size of the human eyes.
5. In 1945 contact lenses were started to be used in the optometry in the America due to suggestions of many American scientists.
6. The first soft contact lenses were made in the 1960 but they came to use in public in 1971.
7. In 1990s the lenses were made more advanced e.g. disposal lenses and daily disposal lenses etc. 

Types:
     There are many types of the contact lenses but they are usually classified to the two types.

1. Hard Lenses
2. Soft Lenses

The hard lenses are those which are made up of the rigid materials such as the polymethylmethacrylate (PMMA). In modern convex lenses the PMMA is usually combined with the others plastic materials to increase their oxygen transparence (passing). 
On the other hand the soft lenses are those which are made up of the soft materials but the classification of the soft and the hard lenses is determined upon its wearing. 
The different types of the contact lenses (soft lenses) are the following.

• Daily Wear Soft Lenses:

                 This type of the contact lenses which is made up of the soft plastic. These lenses are easy to wear. They get easily fitted to the eyes and used in sports usually. But they do not correct all the vision problems like the other some types of contact lenses.

• Disposable Soft Lenses:

                 This type of the contact lenses is only worn for only one to two weeks therefor they are called disposable lenses its all characteristics are well related to that of daily wear soft lenses.

• Daily Wear Disposable Soft Lenses:

                 This type of the contact lenses is only worn for one day means 24 hours these lenses are worn in day while removed at the night so at the next day new pair of lenses is used.

• Planned Replacement Soft Lenses:

                  This type of the contact lenses is replaced on the fixed time or can be said according to the time table these lenses are replaced again and again.

• Extended Wear Lenses:

              This type of contact lenses is usually worn up to a week means up to 7 days then they are replaced.

• Daily Wear RGP Lenses:

               These lenses are made up of the flexible plastic materials.

• Spherical Contact Lenses:

               These lenses retain a single prescription power.

• Aspheric Contact Lenses:

               These lenses are used for astigmatic patients.

• Toric Contact Lenses:

              These lenses contain the characteristics of the both of the spherical and cylinder lenses which are described above and i don't think to explain them again i hope you remembered them.

• Bifocal Contact Lenses:

             These lenses help to provide a sharp view to the eyes as the bifocal eyeglasses are used for but these lenses are much better as compared to the eyeglasses.

• Monovision Contact Lenses:

                  This type of lenses is very much useful and usually used by the opticians in their clinics for checking the near eyesight of the human beings and also for giving a correct measure of the eyeglasses or the lenses to the patients.
                                                   Thanks!
                                      "More you learn more you earn"
I hope i could help you in the topic of contact lenses. 

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