“Seeing stars” is a common visual sensation involving flashes, sparks, or streaks of light. While often fleeting and not a cause for concern, it can sometimes signal an underlying condition.
Understanding Phosphenes
The visual sensations commonly described as “seeing stars” are scientifically known as phosphenes. These flashes of light originate within the eye or brain, not from external light sources. Phosphenes occur when the retina, the light-sensitive tissue at the back of the eye, or the brain’s visual cortex is stimulated by something other than actual light. The brain interprets these internal stimuli as light, creating the perception of various patterns, colors, or flashes.
Everyday Reasons You Might See Stars
Seeing stars can stem from several common and generally harmless situations. One frequent cause is standing up too quickly, a phenomenon known as orthostatic hypotension. When you rapidly change from sitting or lying down to standing, gravity pulls blood into your lower body, causing a temporary drop in blood pressure and reduced blood flow to the brain and eyes. This brief deprivation of oxygen and nutrients to the retina triggers the perception of light.
Applying pressure to your eyes, such as rubbing them, can also induce phosphenes. The mechanical pressure directly stimulates the light-sensing cells in the retina, leading the brain to interpret this activation as light, even without an external light source. Similarly, forceful actions like sneezing or coughing can cause a temporary increase in pressure within the eye or head, stimulating the retina and resulting in flashes of light.
A minor bump to the head can also lead to seeing stars. This occurs because the sudden impact can jar the brain, causing neurons in the visual cortex to fire spontaneously, which the brain then interprets as visual signals.
Medical Conditions Associated with Seeing Stars
While often benign, seeing stars can also be a symptom of medical conditions. Migraine auras are a common example, where visual disturbances like shimmering spots, zigzag lines, or flashes of light precede or accompany a migraine headache. These visual symptoms are thought to result from a wave of abnormal electrical activity spreading across the brain’s visual cortex.
Certain eye conditions can also cause these visual phenomena. Retinal detachment, an emergency where the retina pulls away from its supporting tissue, causes flashes of light, often described as lightning streaks, due to the mechanical tugging on the retina. Changes in the vitreous gel, the clear substance filling the eye, as it naturally shrinks with age can also pull on the retina, leading to flashes.
Systemic conditions affecting blood flow or sugar levels may also manifest as seeing stars. Low blood sugar (hypoglycemia) can temporarily deprive the brain and retina of necessary glucose, impacting their function and leading to visual disturbances. Fluctuations in blood pressure, both very high and very low, can affect blood flow to the eyes and brain, causing visual symptoms. High blood pressure can lead to changes in the retinal blood vessels, while low blood pressure can result in insufficient oxygen supply.
When to Consult a Doctor
While seeing stars can be a harmless and temporary experience, certain signs warrant medical attention. If visual disturbances are persistent, worsen over time, or occur frequently, consult a healthcare professional. Sudden changes in vision, such as an increase in flashes or floaters, especially if accompanied by a dark curtain-like shadow, could indicate a retinal tear or detachment, requiring immediate evaluation.
If seeing stars follows a head injury and is accompanied by symptoms like persistent blurry vision, severe headache, dizziness, confusion, nausea, vomiting, or difficulty staying awake, seek emergency medical care. These symptoms could suggest a concussion or a more serious brain injury. Any new or concerning visual symptoms should prompt a visit to an eye care professional.