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The Stuff That Dreams Are Made Of


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Floaters are the dark shapes resembling specks of dirt or fabric fibres floating in your field of vision. The accepted explanation for these is that they are produced when the vitreous, a gel-like substance that fills about 80 percent of the eye and helps it maintain a round shape, slowly shrinks. As it shrinks it becomes more watery and small, harmless clumps of cells develop and float in the gel. These can cast a shadow onto the retina. (, , ) This must be the case in some circumstances since states: “On rare occasions, floaters can be so dense and numerous that they significantly affect vision. In these cases, a vitrectomy, a surgical procedure that removes floaters from the vitreous, may be needed. A vitrectomy removes the vitreous gel, along with its floating debris, from the eye.”

However this explanation is inadequate for the floaters I see for several reasons:

ABBrightness along ABFirst derivativeSecond derivative

The floaters are bordered by dark line with a lighter line just inside. This gives the appearance of a cell wall. My hypothesis is that what is actually being seen is the second derivative of the noise layer superimposed on the field of view. This is similar to the line detection seen in the ‘shoe’ hypnogogic image. However, the floaters cannot be fully explained by line detection alone. The flicking from one position to another suggests that motion prediction is involved. Sometimes the floaters have red, green and blue fringes which indicates colour enhancement is also taking place.

The fact that floaters are easier to see when lying in bed has been attributed to the debris lying close to the retina. It is actually because shortly after waking up, the visual cortex's image enhancement processes have been ramped up during dreaming.

NHS - Floaters and flashes in the eyes
NIH National Eye Institute - Facts About Floaters
RNIB - Posterior vitreous detachment

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