Saturday, March 8, 2014
ENTOPTIC PHENOMENA IN ROCK ART – FLOATERS:
Picketwire Canyonlands, south of La Junta, Colorado.
Photo: Peter Faris, January, 1995.
“Floaters are deposits of various size, shape, consistency, refractive index, and motility within the eye’s vitreous humour, which is normally transparent. At a young age, the vitreous is transparent, but as one ages, imperfections gradually develop. The common type of floater, which is present in most people’s eyes, is due to degenerative changes of the vitreous humour. The perception of floaters is known as myodesopsia, or less commonly as myodaeopsia, myiodeopsia, myiodesopsia. Floaters are visible because of the shadows they cast on the retina or refraction of the light that passes through them, and can appear alone or together with several others in one’s visual field. They may appear as spots, threads, or fragments of cobwebs, which float slowly before the observer’s eyes. Since these objects exist within the eye itself, they are not optical illusions but are entoptic phenomena.
Eye floaters are suspended in the vitreous humour, the thick fluid or gel that fills the eye. The vitreous humour, or vitreous body, is a jelly-like, transparent substance that fills a majority of the eye. It lies within the vitreous chamber behind the lens, and is one of the four optical components of the eye. Thus, floaters follow the rapid motions of the eye, while drifting slowly within the fluid. When they are first noticed, the natural reaction is to attempt to look directly at them. However, attempting to shift one's gaze toward them can be difficult since floaters follow the motion of the eye, remaining to the side of the direction of gaze. Floaters are, in fact, visible only because they do not remain perfectly fixed within the eye. Although the blood vessels of the eye also obstruct light, they are invisible under normal circumstances because they are fixed in location relative to the retina, and the brain "tunes out" stabilized images due to neural adaptation. This stabilization is often interrupted by floaters, especially when they tend to remain visible.” (Wikipedia)
My old friend.
I have had one floater as an old friend since about the age of seven, shaped like the loop of ribbon used to show support for cancer patients and research (pink), bringing the troops home and supporting wounded warriors (yellow), and other causes, even patriotism (red, white, and blue). I see it again periodically, every few days, usually when looking at a bright sky, slowly moving through my field of vision, and it seems unchanged after all these years. The fact is that I have no way of knowing if it is the same one at all, I may have been seeing a whole series of floaters, but it looks like the same one. The point is that I cannot control when I will see it. Indeed floaters display the interesting phenomenon, that when you try to follow them with your eye they go away faster. I submit that this is perhaps a more mysterious phenomenon than phosphenes, and as such, more likely to have been recorded in rock art. Maybe that is just my opinion, but it is possible.
Wikipedia - http://en.wikipedia.org/wiki/Floaters