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Eye Power????

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Eye Power????

Postby VeenaandNivyah » Fri Apr 07, 2006 11:11 am

Hiii
What causes Power in the eye... that is, short sight and long sight. I am aware that they can be rectified by use of concave and convex lens repectively.... but what is the cause????
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Postby MrMistery » Fri Apr 07, 2006 7:22 pm

Are you reffering to miopia and hipermetropia?
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Postby VeenaandNivyah » Sat Apr 08, 2006 2:58 am

yeah.... the causes?????
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Postby swatkat » Sat Apr 08, 2006 9:47 am

both r caused due to change in lens curvature
myopia is caused due to elongation of the eyeball
thus the image is formed in front of the retina
for hypermetropia the image is formed behind the retina
due to lesser refraction by the lens
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Postby jnkdna » Sun Apr 09, 2006 8:53 am

this may sound immature but how does watching too much tv affect ur eyes? :oops:
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Postby asutoshsahu » Sun Apr 09, 2006 12:24 pm

Lens of eyes have a certain limit to which they can tolerate. The hight energy light beams may harm your eyes.

Am I correct?
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Postby asutoshsahu » Sun Apr 09, 2006 12:29 pm

VeenaandNivyah wrote:yeah.... the causes?????
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As SWATKAT stated the regions it is mostly due to disfunction of ciliary muscles which helps in contraction or relaxation of the eye ball.

I think the blood vessels clot or something else occurs in the ciliary muscles. This can be treated with LASER beam by which the clot melts and the ciliary muscles start functioning. :roll:
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Postby kiekyon » Wed Apr 12, 2006 4:37 am

causes of myopia

Contrary to what some believe, you can be born with the predisposition to myopia and you can also develop myopia to some degree. Most of the information is common knowledge to optometrist but there are varying amounts of agreement when it comes to some of the theories. If you have further questions, you might want to check to see if there is a book for non-optometrists that might clarify even more for you.

Some people are believed to be born with myopia (congenital) or have early development of myopia as the eyeball matures due to the length or size of the eyeball. Axial length refers to the length of the eyeball from its anterior most structure (cornea) to the posterior pole (macula area of retina). This is where light travels through and ultimately rests on the retina as it is refracted (bending light) so it focuses on the retina. The power of the refracting surfaces (cornea and crystalline lens) have to be proportional to the axial length so the images can focus sharply on the retina. A slight increase (tenths of mm) in axial length beyond the proportion neccessary to focus perfectly on the retina, will result in a blurred image. One or two milimeters can result in high amounts of myopia. Generally speaking, axial myopes tend to have higher amounts of myopia than other types of myopes.
Refractive myopia has to do with the refracting surfaces (cornea, lens,) having too much refracting power for a relatively normal axial length. Corneas with too much power can induce generally less amounts of myopia than axial length myopia. This too can be passed on genetically. Some people can have a combination of axial and refractive myopia. LASIK surgery is composed of essentially decreasing corneal refractive power so as to decrease substantially or even eliminate myopia. Cornea power can also change over time from injury, disease, gravity, or even for unknown reasons!

Lastly, some people can develop relatively small amounts of myopia from the changes in the crystalline lens. This lens is responsible for dynamic movement that allows us to focus on near objects. If you tried to focus at a near object and then look far away immediately (very hard to) it would seem blurry for a very short time because the lens created a temporary state of myopia. There are theories that some people who have constant lens movement and physical stress to the lens can develop myopia. I believe there is some truth to that as the eye was not developed to do so much near demands we put on them in modern life. There are many studies done and other theories as to how we develop relatively low to moderate amounts of myopia. Some people who have to see in the dark for extended periods of time can develop some myopia
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