It is hard to believe this. But contact lenses orgininated in 1508 when Leonardo Da Vinci sketched and described various forms of lenses as in:
Hard lenses are made from a rigid material in the form of Polymethylmethacrylate or PMMA. This substance is being mixed with other plastics in increasing oxygen permeability.
They are manufactured from a rigid material, PolyMethylMethacrylate (PMMA). This substance is also combined with other plastics to increase the oxygen permeability and perfect visual acuity.
In 1632, Rene Descartes from France recommended the first hard lenses. His idea culminated in a quarter inch long and water-filled tube whose outer end was attached to a microscopic lens. Expermentating on himself, he became the first user.
In 1887, F.E Muller - a German Glassblower - fabricates the first piece of glass acting as lens which could be seen through and tolerated.
Soft lenses have the main advantage of allowing the eyes to be oxygenated through the lens.
The are easy to adapt to and difficult to lose. They are available in all types of colours and great to wear in sport activities.
However, they have to be thoroughly cleaned everyday and can last up to 1 year maximum.
Disposable lenses come in 2 forms as in:
1. Extended Wear Disposable
They enable you to wear up to six nights after which you can throw them away. They do not require any cleaning and have virtually no chance of causing eye infection if you follow its instructions.
You can get them tinted and as bifocals. Your eyesight 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 enable you to wear on a planned schedule. Be it fornightly, monthly or quarterly.
However they require thorough cleaning and disinfection at all times.
There are 4 types of colored lenses as in:
1. Visible Tints,
2. Tints To Enhance,
3. Color Opaque Tints and
4. Tints That Filter Light
Most of them are available in plano form (without visual correction) and for astigmatism who need bifocal correction or frequent replacement lens.
Astigmatic or toric lenses were first introduced and approved for distribution in US in 1978.
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.
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