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Post Info TOPIC: Corneal curvature as a function of distance to the object.


Executive

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Posts: 437
Date: Wed Aug 24 1:46 PM, 2005
Corneal curvature as a function of distance to the object.
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Hello, just find it amazing...It's just that sometimes I feel my KC also depends on what I look at...


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 J Vis. 2003;3(7):456-63. Epub 2003 Aug 5.


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Change in corneal shape and corneal wave-front aberrations with accommodation.

He JC, Gwiazda J, Thorn F, Held R, Huang W.

Myopia Research Center, New England College of Optometry, Boston, MA, USA. hej@ne-optometry.edu

This study investigated the change in corneal curvature and corneal wave-front aberrations with accommodation. The corneal curvature of the right eyes of 12 young adults was measured using a corneal topography system, while subjects fixated far (4.0 m) and near (0.2 m) targets with their left eyes. Convergence was controlled. Both the mean corneal radius at the vertex and the shape parameter significantly increased from the far to the near viewing condition. No significant change in root mean square of wave-front aberrations with accommodation was observed for the group, but there was individual variation in the change of wave-front aberration. A significant mean change for the group in both x-axis coma and spherical aberration was found. The change in corneal surface with accommodation suggests an increase in peripheral curvature with flattening at the vertex.



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yarsky
Anonymous

Date: Wed Aug 24 10:55 PM, 2005
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I must say Yarsky I don't understand fully the study...

I think contrasts are harder....like the contrast of a shiny piece of metal in the sunshine.

...and also how the light travels....when i have been on holidays near the equator...i have not had much problems at all compared to being somewhere where it is cloudy all the time...i think the light hits the equator at 90% at the equator and so do not shatter first...and with hardly no clouds thhe clouds then do not shatter the clouds either!

Morning is also good...as the ligh is traveling horizonally from the horizon...and so goes straight in to the eye with out light coming from shatter for different angles to the eye.

fluresant (spelling?) is not like natual light...it as well shatters and so is a problem for kcers.

Anyway All the Best.

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Executive

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Posts: 437
Date: Thu Aug 25 3:30 PM, 2005
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The brightness of the light is important for it chages the size of the pupil and this has its own effects on our vision. In daylight I see better. In twilights or somber days worse.


What I find surprising in the strudy above is that...See, the cristaline changes the shape when accomodating (if the object is close it becomes more convex, if far - less convex). Cornea is a lense also, that does 2/3 of the overall fcalisation job. So, the resluts show that corneal curvature, as that of the cristaline, also depends on the distance to the object: it becomes more steep when the object is close, and less steep when the object is far How does that happen for cornea does not have muscles attachet to it? Right, but it is surrounded by sclera, and the sclera reacts on these things and transmits this signal, purely mechanicaly, to cornea. It looks like this Conclusion: for us it is better to leave the computers far behind, go to the seeside, or country side, relax...



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yarsky
Anonymous

Date: Thu Aug 25 11:15 PM, 2005
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You know...that is very interesting... i did not know that... may be that function is defunct for us? or may be not?

Anyway thanks Yarsky as i learnt something today and its true you do learn something new every day!! ...i've had my quota for today so i'll say ciao for now!!

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