In hopes of turning this phenomenon into improved vision for the blind, scientists have developed a cortical visual prosthesis, implanted in the visual cortex, that generates patterns of phosphenes. The device has been approved by the FDA for clinical trial. As Alcmaeon rightly pointed out, there are causes for the bursts of light beyond just rubbing your eyes: Getting hit in the eye can produce this phenomenon—as can a sneeze, a surprisingly powerful event that tends to clamp our eyes shut, Wen says.
MRIs, for example, produce a changing magnetic field which can stimulate the visual cortex, making a person see these flashing lights. When it comes to an EEG, depending on the brain stimulation frequency band Hz used, some patients experience the phenomenon when closing their eyes, which is believed to come from retinal stimulation during the process. And the activity doesn't only happen on Earth; astronauts in space have also been known to experience them.
As reported in in the journal Vision Research, "over 80 percent of astronauts serving in today's NASA or ESA European Space Agency programs have perceived phosphenes at least in some missions and often over several orbits.
You may also see a dark tail with the dot of light, which is a bunch-up of red blood cells behind the slower-moving white blood cell. Seeing moving dots when staring at a clear sky is normal. The white blood cell movement is a normal function of the eye, though not everyone notices the moving dots in their vision.
Moving dots caused by the blue field entoptic phenomenon are all the same size and shape. If the eye stops moving, the spots keep whizzing around. In contrast, floaters, which are clumps in your vitreous, the gel-like fluid in your eye, differ in size and brightness. If the eye stops moving, the floaters settle down. They often occur when pressure on the eye stimulates the retina.
The retina is a light-sensing part of the eye. Pressure can be caused by an outside force, such as rubbing your eyes, or internal structural problems or inflammation. Photopsia can also occur with migraines, changes in blood pressure or blood flow to the brain, or brain damage. Photopsia is usually harmless. However, if you see them often, tell your healthcare provider or eye doctor. If you have other symptoms like a shadow or curtain in your vision or an increase in floaters, get emergency help right away.
Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Photopsias: A key to diagnosis. Visual snow: Visual misperception. J Neuroophthalmol. Posterior vitreous detachment - prevalence of and risk factors for retinal tears. Clin Ophthalmol. American Society of Retina Specialists.
Posterior vitreous detachment. Updated Differential effects of HCN channel block on on and off pathways in the retina as a potential cause for medication-induced phosphene perception. Invest Ophthalmol Vis Sci. The clinical characteristics and neurophysiological assessments of the occipital cortex in visual snow syndrome with or without migraine. American Migraine Foundation. Understanding ocular migraine. October 19, Your Privacy Rights.
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