Phosphenes are flashes of light that appear without an actual light source. They cause a visual phenomenon called photopsia (seeing stars).
Phosphenes stimulate the retina like a light source but come from inside the eye (entoptic phenomena). They’re commonly caused by increased pressure on the eye caused by rubbing, sneezing, and bearing down.
They can also be caused by eye trauma and optic nerve inflammation. While phosphenes usually go away after a couple of seconds and are nothing to worry about, persistent photopsia can result from an underlying medical condition.
What Do Phosphenes Look Like?
Phosphenes are described as illusionary flashes of light that chaotically move across the visual field, including:
- Darting flashes of color
- Temporary dots
- Squiggles
- Swirls of light
- Geometric patterns
Phosphenes are also linked to visual hallucinations, which include more complex, picturesque images. These are typically caused by drugs, alcohol, stress, fever, or psychotic conditions.
Other Common Symptoms of Phosphenes
Classic symptoms of phosphenes include flashes of light, stars, and squiggly lines that move across your field of vision. Other common symptoms of photopsia include:
- Visual snow (static or fuzz in the visual field)
- Bright colors
- A light that shimmers and twinkles
- Flickering zig-zag lines
- Shapes or dots that appear to be floating
What Causes Phosphenes?
Phosphenes usually appear because of stimuli that directly activate your visual system. Here's how:
- Mechanical pressure. Rubbing your closed eyes forcefully stimulates the retina, making you “see stars."
- Electrical and magnetic fields. Techniques like transcranial magnetic stimulation (TMS) can directly activate the visual cortex in your brain, producing vivid phosphenes. Powerful magnetic fields, like those used in MRI scans, can also induce phosphenes by generating electrical currents near your eyes.
- Radiation. Exposure to X-rays and other forms of radiation can excite the light-sensitive cells in your retina, leading to visual sensations.
- Neurological activity. Electrical stimulation of specific brain regions involved in vision can also generate phosphenes.
- Medication side effects. Some medications can have the unexpected side effect of producing luminous phenomena that resemble phosphenes.
How to Get Rid of Phosphenes
Since phosphenes are a side effect of visual stimulation or various health conditions, removing phosphenes includes eliminating the stimuli and treating the underlying medical condition.
While many cases of phosphenes go away on their own (migraine, optic neuritis), they could become permanent if structural damage occurs to the eye or brain. This suggests that the underlying condition is worsening.
When to See a Doctor
Occasional phosphene perception is common and typically goes away after a few seconds.
However, if phosphenes are persistent and don’t go away on their own, you should see a doctor, especially when they are accompanied by:
- Headaches
- Weakness
- Dizziness
- Double vision
- Nausea or vomiting
- Low blood pressure
- Loss of consciousness
- Numbness
Consider getting routine comprehensive eye exams. Not only are they great for maintaining your eye health it can also catch vision problems related to phosphenes early.
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