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How has the Invention of Contact Lenses affected people's Sight?

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Introduction

Manon Mollard MP5a                                                                                      14.12.04

Biology: The Impact of Man’s Inventiveness on the Human Body.

How has the Invention of Contact Lenses affected people’s Sight?

Introduction

        People with sight troubles have had the possibility of wearing glasses for a really long time, but the new technology made available contact lenses. In this essay, I am going to look at the different contact lenses types that exist, at who invented them and when, for which vision problems they are solution, at how to take care of them, at how common they are in our society and finally, I will write about my own opinion.

What contact lenses are

According to the Macmillan Dictionary (2002), contact lens may be defined as “a plastic lens that you wear in your eye to help you see more clearly”.

A very wide variety of contact lenses are available in today’s society, including hard and soft (even if soft is by far more common now), disposable and extended wear; this makes it easy for each person to chose the appropriate type of contact lens for her. The main types of contact lenses are listed below:

  • Soft lenses: As these lenses are soft, they are made of a large percentage of water, and this allows oxygen to pass through the lens and reach the cornea. They are also more comfortable and easier to adapt to.
  • Rigid-gas permeable lenses: these lenses are not made of water so they are not as comfortable as the soft ones, but they do allow a larger amount of oxygen to pass through them. Their best advantage is that they offer a excellent sight correction.
  • Disposable lenses: Disposable means that the lenses are worn for a definite period (from two weeks to six months depending on the lenses) of time before being thrown away and replaces by a fresh new pair. The fact of throwing out the lenses helps making sure the lenses are always very clean, so healthier and more comfortable.
  • Extended wear lenses: these lenses are made to be worn 24h a day, and up to seven days on a row (a new type made of ‘silicone hydrogel’ allows more oxygen to flow in so that they can be kept for up to 30 days without taking them off).
  • Bifocal contact lenses: this type of lens has two major functions: to correct distance vision and to correct near vision. There are two main designs: the power or seeing far is concentrated at the top and the one of seeing nearby at the bottom, or the different powers are blended on different parts of the lens.
  • Coloured contact lenses: they can be used to correct existent sight troubles, but also just to look prettier, as they come in a large variety of colours, from hazel to blue, passing by grey, purple and green.
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Middle

  • Astigmatism: this condition usually affects both nearsightedness and farsightedness because the cornea’s curvature is rather oval when it should be round. Their sight is not précised and for example, they can confuse the letters M, N and H, or B and D. It is often associated to myopia or hyperopia.
  • Hyperopia: this is a long-sightedness condition, and people affected by it have difficulties to focus on close objects, while the sight of distant objects stays correct. It might be because the cornea is too bulging, or because the crystalline lens (see eye diagram) of the eye is too flat.
  • Myopia: also known as short-sightedness, people affected by this condition are able to do tasks that require a vision of nearby objects, such as reading or sewing; but they see distance objects blurred so for example, they cannot read highway signs.
  • Presbyopia: this long-sightedness condition cannot be avoided because it touches everyone at some point in life (usually around 40-50 years old). It is due to a loss in flexibility of the lens and loss of power of the ciliary muscles and it cause the person to have difficulties in focusing on nearby objects. A person affected by this condition will for example hold her newspapers further away from her eyes to see it better (we say that the “arm grows shorter” because it is not able to hold the object at a distance long enough for these people to see anymore).
  • Strabismus: this condition, also called lazy eye, makes us squint; there is a lack of coordination between the muscles of the two eyes, and this means that the vision axes of our two eyes are not parallel so they don’t point out at the same direction. This affects our depth perception.

The following eye diagram will help understand which parts of the eyes are damaged by the previously explained conditions:

image02.png

image03.pngimage00.png

image04.pngimage01.png


How to use them

You definitely need to consult a specialist who will tell you the type of contact lenses that are the most appropriate to your case: the optometrist will prescribe the lenses to you and the oculist will provide them. Your ophthalmologist will explain you how to put them on; it might look hard at the beginning but it’s just a matter of getting used to it. But two rules are still primordial: to make sure you have clean hands before you put your lenses in your eyes and not to wear them for than the indicated time.

It is very important to take care of you contact lenses; indeed they need regular cleaning and disinfecting to retain clear vision and prevent infections. Eyes were not designed to have a foreign object in them. Plus this ‘foreign object’ prevents the air to reach the eye, while this sight organ needs to receive oxygen. Contact lenses make your eyes vulnerable to all sorts of things so by cleaning them, they are less likely to breed bacteria and they are more air permeable. A large variety of products is nowadays available to clean, rinse and disinfect your lenses:

  • Saline solution: once the lens was cleaned, this solution is used to rinse it.
  • Daily cleaner: this cleaner is used once a day, to clean the lenses. With a few droplets of the cleaner on it, the lens is rubbed for about 20 seconds on each side. Long nails mean to be extra careful with the rubbing!
  • Multipurpose solution: this solution is used for rinsing, disinfecting, cleaning and storing the lenses. It can be used only for disinfection and storage if it is associated with another rinsing product (eg: Saline solution) and a cleaning one (eg: daily cleaner).
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Conclusion

Conclusion

In conclusion, the invention of contact lenses has greatly affected people’s sight: eyeglasses are not the first solution to solve vision troubles anymore, because contact lenses have replaced them. They have been so successful because they are easier to use, more discrete and practical as well. And it is more and more common to see people wearing coloured ones them only for the fashion side.

However it is important to remind that their first purpose was for medicine, and they require special care that people have to follow, even if they just contacts as fashion accessories.

Bibliography:

  • Articles (online)
  • Bellis, Marie; “Glass, Mirrors, Eyeglasses, Sunglasses, Contact Lens”; 2002. Available on the World Wide Web: http://inventors.about.com/library/inventors/bleyeglass.htm
  • Books:
  • 100 greatest medical discoveries ; Roystn, Angela ;  Dragon’s world (Great Britain – Surrey; 1995)
  • Macmillan English Dictionary ;
  • The Usborne internet-linked complete book of the human body; Claybourne, Anna; felicity Books (Cambridge)
  • Internet Websites:
  • http://id.essortment.com/contactslensca_rrxv.htm -PageWise, Inc-
  • http://www.newsandevents.utoronto.ca/bios/askus17.htm
  • http://www.augen.de/American/Brille_u_linsen/brillen.html
  • http://www.doctissimo.fr/html/sante/bien_voir/bien_voir_niv2.htm
  • http://www.visionhelp.com/terms.htm#terms
  • http://www.allaboutvision.com
  • http://www.encyclopedia.thefreedictionary.com  

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