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Black and white

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Black and white

Postby hoiki426 » Thu Jan 12, 2006 8:21 am

1.)When in bright condition
The black and white colour is detected by cone or rod?

My book said"Rod is for black and white vision"

but.....

I have done a HKCEE mc(30/99)
It said:

"When you are reading through a page , only a few words can be seen clearly each time.This is because

only a few words can be focused onto the yellow spot each time."

There is just cone on the yellow spot and the words on the book is usually black in colour.........................................


The black and white colour is detected by cone or rod?

2.) What kind of eye disease will be caused if our lens is not elastic?



Th for answering me so many questions~><
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Postby Dr.Stein » Thu Jan 12, 2006 9:45 am

RODS are more sensitive to light than are cones, and rods are particularly important for night vision. The outer segment of rods is an elongate cylinder of cytoplasm. Within this is column of discs which are flattened membrane bubbles whose contents are technically extracellular. These hollow wafers are produced continuously from the basal portion of the outer segment, forming as projections of cytoplasm that serially fuse to form the discs. These mature discs are not connected at all to the plasma membrane.

CONES operate at higher light intensities and are the main receptor of "daylight" vision, since rods saturate at very low light levels and essentially cease to function. All color distinction is due to cone function, based on the existance of three subtypes of cones sensitive to three distinct light wavelengths. Rods respond only to one narrow band of light frequency, and rod-only retinas are entirely colorblind. Cones have a much shorter outer segment than do rods, and the developing membranous processes that in rods fuse into the disc series--remains unfused in the rods. This gives these cells the appearance of bearing a kind of comb on their outer segment, but keep in mind that in 3-D, that is really a series of plates joined at the ciliary end.

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Postby hoiki426 » Sat Jan 14, 2006 6:18 pm

So...
I still have one question.

What kind of eye disease will be caused if our lens is not elastic?
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Postby MrMistery » Sat Jan 14, 2006 9:22 pm

This occurs in old people. As you get older, it is harder and harder to see things close to you. Punctum proxim moves from 7 to 80 centimeters away from the eye. The condition is called presbyopia
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Postby Dr.Stein » Sun Jan 15, 2006 1:10 am

Here it is the figure of presbyopia :)

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Postby MrMistery » Sun Jan 15, 2006 7:56 pm

At the rate you are posting pictures and i am saving them, i will have your entire collection by next year.
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