floaters
The eye is filled with a clear liquid. In the liquid are a few
floating cells which have broken away from structures within
the eye. You probably have occasionaly seen some of those
floating cells but didn't know what they were.
The floaters are sometimes seen when you look at the daytime
sky. Here is a somewhat improved way to see some of the
floaters. Use a pin to make a hole in a piece of paper. Hold
the paper as close to the face as possible and look through
the hole with one eye. You must look at a brightly lit scene
such as the daytime sky or the inside surface of a lamp shade.
If the bulb in the lamp is 60 watts or less you may get
better results by looking through the pinhole at the bulb, if
it is frosted or coated. If looking at the bulb it would seem
sensible to avoid too intense light with the following
precautions: do not have the eye closer than 1 foot from the bulb,
do not use a bulb of over 60 watts, the pinhole should not be
larger than the pin's diameter, use only the common
incandescent filament type bulb that is frosted or coated, and
limit viewing time to a few minutes. According to the book
'Know It All: The Fun Stuff You Never Learned in School'
floaters are all that's left of the hyaloid artery. That
artery supplied the eye with blood before you were born and
were in the womb. Then when the eye was finished growing
that artery was no longer needed. It shrank and broke into
the tiny pieces that you can still see as floaters.