Myopia and Hyperopia are two different conditions which occur due to the incorrect shaping of the lens causing the light rays entering the eye to not focus on the retina creating a blurred vision.......

Myopia


Presbyopia

  • Commonly referred to as “shortsightedness”.
  • Lens is constantly thicker and has high curvature.
  • People suffering from Myopia are able to see closer objects without problem however when viewing distant objects have blurred vision.
  • Light rays from distant objects are focused in front of the retina.
  • Can be corrected through concave lenses.
myopia_big.gif
Figure 7.1 represents the condition of Myopia, in the top image, where the light rays are focused in front of the retina. The bottom image represents the correction of Myopia through the use of a concave lens in order to focus the light on the retina.

  • Commonly referred to as “farsightedness”.
  • Lens is constantly thinner and has less curvature.
  • People suffering from Presbyopia are able to view distant objects with no problems but have trouble viewing closer objects due to blurred vision.
  • Light rays from closer objects are focused behind the retina.
  • Can be corrected through convex lenses.
hyperopia_big.gif
Figure 7.2 represents the condition of Hyperopia, in the top image, where the light rays are focused behind the retina. The bottom image represents the correction of Hyperopia through the use of a convex lens in order to focus the light on the retina.


From this we can gather that Myopia occurs in people who have trouble seeing long distances and is caused by the constant higher thickness and curvature of the lens and the focusing of light in front of the retina. This differs from Hyperopia as people suffering from this condition can view far objects fine but have trouble viewing closer objects caused by the constant thinness and less curvature of the lens and the focusing of light behind the retina.
The most common solution to these conditions are the use of corrective lenses to bend the light slightly before it enters the eye. People suffering from Myopia would wear concave correction lenses in order to spread the light slightly just before entering the eye. However people suffering from Hyperopia would use convex corrective lenses in order to bend the slightly straighter before entering the eye. Contact lenses work in a similar way to corrective lenses but are becoming increasingly popular as they are less noticeable and can be purchased in a variety of colour to effectively change the colour of your eye.

Figure 7.3 represents roughly what a person with Myopia would see, with the short-sightedness being fine to see however having blurred long sighted vision.
Figure 7.3 represents roughly what a person with Myopia would see, with the short-sightedness being fine to see however having blurred long sighted vision.
Figure 7.4 represents roughly what a person with Hyperopia would see, with them able to see long-sightedness without trouble however have blurred short sight vision.
Figure 7.4 represents roughly what a person with Hyperopia would see, with them able to see long-sightedness without trouble however have blurred short sight vision.

























Another technology used to correct Myopia and Hyperopia include radial keratotomy and photo-refractive keratectomy. Both of these are surgeries which invole the altering of the refractive power of the cornea. In radial keratotomy fine surgical instruments shave small amounts of corneal tissue off the eye while in photo – refractive keratectomy a computer controlled laser is used to remove thin slices of corneal tissue. {Aubusson, Eileen Kennedy Peter. Biology in Context: the Spectrum of Life. Victoria : Oxford Uni. Press., 2001. Print. page 474}





















http://www.youtube.com/watch?v=NH15CxVXts4 is the video to the left which gives a explanation of the process of radial keratotomy. http://www.youtube.com/watch?v=I6pqb6YzeN8 is the video on the right which explains the process of photo-refractive keratectomy.


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