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Trivia tidbit...............Katlillie |
When you press on or rub your closed eyes, do you sometimes see colors, lights and patterns flicker in the black space? This phenomenon has a name, which I learned today at my eye doctor's appointment......entoptic phenomena........
Entoptic phenomena are visual effects whose source is within the eye itself. Under suitable conditions light falling on the eye may render visible certain objects within the eye itself. These perceptions are called entoptical. (Occasionally, these are called entopic phenomena.)
They are different from optical illusions, which are perceptual effects occurring within the brain. Most entoptical phenomena have a direct, known physical cause. However, like optical illusions or hallucinations, the observer of an entoptical effect cannot give others a direct view of what he or she observes. During the 1920s, some theosophists, unaware of the physical explanation, maintained that the moving spots seen in the blue field entoptic phenomenon were "vitality globules" related to the concept of prana in yoga.
Some examples of entoptical effects include the following:
A phosphene:
is the perception of light without light actually entering the eye, for instance caused by pressure applied to the closed eyes.
Floaters:
or muscae volitantes are slowly drifting transparent blobs of varying size and shape, which are particularly noticeable when lying on the ground looking up at the sky. They are caused by imperfections in the fluid of the eye.
The blue field:
entoptic phenomenon has the appearance of tiny bright dots moving rapidly along squiggly lines in the visual field. It is much more noticeable when viewed against a field of pure blue light and is caused by white blood cells moving in the capillaries in front of the retina.
Haidinger's brush:
is a very subtle yellow-and-blue pattern that is seen when viewing a field of light that is polarized.
The Vascular figure:
is an image of the retinal blood vessels in one's own eye. It can be seen by shining a bright, moving light like a penlight onto the sclera (the white of the eye) in a darkened room. Normally the image of the retinal blood vessels is invisible because of adaptation. The unusual angle casts the image onto unadapted portions of the retina. Unless the light moves, the image disappears within a second or so. If the light is moved at about 1 Hz, adaptation is defeated, and a clear image can be seen indefinitely. The vascular figure is often seen by patients during an ophthalmic examination when the doctor is using an ophthalmoscope. In the process of aligning the instrument so that the doctor can view the blood vessels through the pupil, the light from the instrument often falls briefly on the sclera, so that the patient gets a quick glimpse of the vascular figure.
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| Alias | Date | Reply |
| ~Silver Alexis~ |
2/16/2006 9:02:00 PM |
Extremely interesting... and now I won't fear for my eyesight...but hey...ask your eye doctor about this one...maybe it fits the profile. Extremely thin wormlike silver strands always just to the side of where your eyeball is turning. I see these alot. In the dark and light..outside in the sun or inside in house lighting. Always wondered if I was imagining them...but I know Im not. |
| WitchyPoo |
2/17/2006 2:49:00 AM |
Yes, I used to do it all the time as a child just to see the pretty colours....LOL! |
| Bad Co |
2/19/2006 11:45:00 PM |
Katlillie :) How cool, lady! I've actually wondered about that ever since I was a child. Those colors, yes.:) I can just see you posing that question to the doctor.:) I like the way that you think. Thanks for this. Write on..... |
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