Index

Seeing Spots or Lights


Seeing spots or dots is a frequent complaint. Many subjects find it difficult to provide detailed descriptions and very few are prepared to illustrate their observations graphically. Indeed, graphic libraries of spotted vision seem to be lacking. Part of the difficulty of coming to grips with symptoms like these is the difficulty of rendering movement, which often is an integral part of the experience. Computer graphics offers a solution to this problem. One application that immediately may come to mind is the simulation of the flying corpuscle or bluefield phenomenon that most everyone perceives when gazing at a uniform blue field of high luminance. The phenomenon consist of faint spots swirling around the line of sight, in synchrony with the heart beat. These spots are held to represent leukocytes passing through the perifoveal capillaries. Being transparent, the leukocytes transmit incoming light to the underlying photoreceptors. Move the cursor over the image to start the animation.

The second most common observation of spots or dots presumably relates to mouches volantes or floaters, which usually present another highly characteristic movement pattern. A dynamic floater simulation is presented elsewhere on this site.

Other types of spotted vision may be approached similarly, as attempted in the display below. The idea is to try to find an approximate match to the subject's symptoms and to obtain a rough quantitative measure. Select mode, size and numbers of spots, spot color and opacity, and rate of movement, to obtain as close a match as possible. To obtain a permanent record, tap the PrintScreen keyboard key, open a paint programme, and select import from Clipboard. The resulting image can be cropped and and saved. Feedback regarding possible improvements would be most welcome. Except for the bluefield phenomenon, optospotometry is a poorly explored field.


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Dot & Spot Simulator     © L. Frisén 2007

Mode Number Size Delay

A peculiar variant of spotted vision that recently has attracted much attention is so-called "visual snow": there are even some websites dedicated to this subject (e g, 1, 2). Visual snow may be simulated in the display with settings like

Visual snow has no known associations with disease. One of my patients thought of her visual snow as "tinnitus of the eyes". Perhaps soundly.

"Pixelized " and "noisy" vision are yet other fairly intuitive descriptions. Both terms are borrowed from computer graphic procedures. Pixelization refers to the breaking-down of images into featureless blocks. The above display can show an example (select Pixelize under Mode). Examples of noisy images are shown in the unstable vision section. These types of phenomena are not uncommon in the hypnopompic state, that is, when leisurely waking up after normal sleep. Again, there are no known associations with disease.

Visual snow, pixelized vision, and noisy vision are always bilateral phenomena. Actually, most variants of spotted vision appear to be binocular, indicating that the generators generally reside outside the eyes themselves.


New 2016: a refined version of the above display has been included with a host of other symptomimetic displays in a new dynamic visual library. The library has the format of an iPhone/iPad app named Vision Sx.


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