Re: back to school

Date: Wed Feb 06 2002 - 15:29:37 MST

Scerir forwards:
> << In order for the eye to be able to focus an image on the retina,
> the axial length of the eye needs to be just right. If the eye is too
> long (or too short), then the image is perpetually focused in front
> of the retina (or behind it). The result is nearsightedness (or
> farsightedness). It turns out that the retina of the eye plays a big
> role in making sure that the axial length of the eye is just right.
> How? Well, the retina has the ability to determine whether an image
> is "in focus" or "out of focus." If an image is "out of focus" then
> the retina emits chemical signals that control the growth of the eye,
> making it either longer or shorter, as needed, so that the image can
> be focused properly.

Interesting phenomenon. The other obvious question is, even if the
retina can tell that the image is out of focus, how does it know whether
the focal plane is in front of or behind the retina? In other words,
how does it know which way to grow in order to correct the problem?
That sounds even harder than determining whether the image is in focus
or not.

I wonder if they are barking up the wrong tree, and it is a signal from
the lens that does the trick, maybe some subtle chemical wafting through
the vitreous humor.


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