TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > The History, Advantages and Disadvantages of Contact Lenses
Contact lenses, a relatively new invention, have allowed people with eye disorders who may have had to previously wear glasses have been given the chance to wear contact lenses as an alternative.
History of contact lenses
- First contacts made from glass shell filled with animal jelly.
- Idea first thought about in early 1800s
- Many problems with early lenses, very unhealthy for the eye
- Originally very uncomfortable
- 1930s saw the discovery of polymers
- First hard lenses created in 1950s
- First soft lenses created in 1960s
- First gas-permeable lenses created late 1970s
Disorders
- Myopia (Nearsightedness)
- Presbyopia (Light refracted too much on one side)
- Hyperopia (Longsightedness)
- Astigmatism (Distorted curving of images)
As time moved on, so did the progression of materials used for contact lenses, these were developed into three distinct types. These are soft, hard and gas permeable lenses. There are suitable materials used for each type of lens giving each its characteristic properties. Each has advantages and disadvantages that can be summarized in the following table:
| Lense type
| Advantages
| Disadvantages
|
| Soft lenses
|
- Comfortable
- Allow oxygen to penetrate
- Very Hydrophilic
- Daily disposables available
- From 99p per day!
- Some 69% water
- Ultra thin edges
|
- Clarity of vision is inferior to hard lenses due to high water content
|
| Hard lenses
|
- Durable, can last for several years
- High clarity of vision
|
- Not gas-permeable
- Expensive
- May take weeks for them to feel comfortable
- A wetting solution is required
|
| Gas-permeable lenses
|
- Reasonable clarity of vision
- Oxygen can penetrate
- Comfortable to wear in about 3 hours
|
- Often inflexible
- Expensive
|
These are not the only types of lens available; there is a broad range of which these are the most preferred. Other lens types include:
- Toric lenses (To correct astigmatisms)
- Bi-focals (Correct vision two ways i.e. reading glasses)
- Daily disposables (Soft lenses)
- Monthly disposables (Gas-permeable lenses)
- Coloured/novelty contacts (Any type, often soft disposable)
- Extended wear lenses (Hard lenses)
Physical properties of polymers
Polymers are without exception the current most suitable material for contact lenses to be made from, they have a variety of properties:
- Transparent (Amorphous)
- Flexible (In some cases)
- Low density around 1000 kg/m3
- Hydrophilic
- Gas-permeable
- Tough around 100kj/m2
- Un reactive
- Easy to manufacture
- In abundance
- Moldable
- Suitable refractive indices around 1.5 - 1.6
Social / economic factors influencing contact lenses
- No age restrictions however elderly find them more difficult to use
- Britain was originally very reserved about wearing contact lenses
- Sales now rising due to cheap disposable lenses
- Sales rising due to young generations growing up with them
- Some health worries between younger generations
Future of contact lenses
As they become more popular, the companies are able to spend more money researching the different types of materials which may be able to be used in the future enhancing the physical properties of the material and also the cost of materials. As it is already there are many people which are able to buy contact lenses for fun, choosing coloured or design contact lenses. They are definitely beginning to rival glasses and may eventually become the more preferred option among future generations.
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