We wear contact lenses mainly because we are vain.
But, they come in handy for any kind of sports, people even wear them while swimming although you have to watch they don't float out.
The Inventor of the contact lens concept was Leonardo da Vinci in 1508,who sketched and described several forms of contact lenses.
Hard contact lenses
Hard contact lenses are manufactured from a rigid material, PolyMethylMethacrylate (PMMA). This substance is also combined with other plastics to increase the oxygen permeability.
Visual acuity is perfect.
In 1632 Rene Descartes of France suggests the first hard contact lens, which idea was actually developed in 1801 by Thomas Young; resulting in a quarter-inch-long, water-filled glass tube, the outer end having a microscopic lens,and he is the first user.
In 1887 a German Glassblower, F.E. Muller of Wiesbaden,fabricates the first piece of glass acting as a contact lens which could be seen through seen through and tolerated.
Soft daily wear lenses have the main advantage that they allow the eyes to be oxygenated through the lens.
They're also easy to adapt to and difficult to lose. You can get them in all kinds of colours. Fantastic for wearing in sport activities.
Not a panacea for all vision problems and they have to be thoroughly cleaned. Maximum lifespan 1 year.
In 1936 William Feinbloom, a New York optometrist, manufactures the first American- made plastic contact lenses. These were still hard lenses.
The first soft, water-absorbing plastic lenses were developed in 1960 by Otto Wichterle and Drahoslav Lim .
Disposable lenses
1.Extended-wear disposable
Soft lenses that you are able to wear for an extended period of time, up to six nights, and then you can throw them away. They hardly require any cleaning and have virtually no chance of causing eye infection if user instructions are followed...
You can get them tinted and as bifocals. Your Vision may not be as sharp as with other lenses and they do not correct all vision problems. More difficult to handle.
2. Planned soft daily replacement lenses
Soft daily wear lenses that you replace on a planned schedule, either every two weeks, monthly or
quarterly. Require thorough cleaning and disinfection. all vision problems. Not easy to handle.
Colored lenses
There are 4 types of colored contact lenses:
visible tints,
tints to enhance,
color opaque tints and tints that filter light
Most of these colored contact lenses are available in plano form (without visual correction), as well as for astigmatism, who need bifocal correction, or who want a disposable or frequent replacement lens.
Astigmatic lenses (toric) were first introduced in 1978 and approved for distribution in the United States.
These lenses contain both a spherical and cylinder component to correct prescriptions which have astigmatism. Lenses may be thicker in one meridian or have modified thickness profiles to enable the lens to maintain the correct orientation on the eye.
Bifocal contacts became available in 1982 for commercial distribution.
There are a variety of designs in bifocals, essentially all trying to provide a transition or reading zone for use at near distances. The different designs include; + aspheric multifocal - + simultaneous vision concentric - has either a central near or distance zone with surrounding zone of opposite type to centre (eg, centre near,distance surround) + diffraction/holographic - based on diffraction grating principles.
Eye exercises
There seems to be a natural alternative to eyeglasses, contacts, intacs, and even Lasik surgery, which is a series of eye muscle exercises over a period of 30 days that supposedly corrects your vision to quite an extent.
The validity of this method of vision correction has not been fully proven. |
