Phosphenes are the perception of light without actual light entering the eye, often described as seeing “stars” or flashes. This common visual phenomenon can occur due to various stimuli, ranging from everyday occurrences to underlying medical conditions. Understanding phosphenes helps distinguish between harmless instances and those that may signal a health concern.
Understanding Phosphenes
Phosphenes are visual sensations of light generated internally, rather than from an external light source. These perceptions can manifest as flashes, sparks, dots, squiggles, swirls, or patterns of light and color. This phenomenon occurs when the retina, the light-sensitive tissue at the back of the eye, or the visual pathways in the brain are stimulated by something other than actual light. The brain interprets these internal signals as visual input, leading to the perception of light. While typically brief, lasting only a few moments, phosphenes can sometimes be a recurring experience.
Common Causes of Phosphenes
Many factors can trigger phosphenes, with some of the most frequent being generally harmless. Mechanical stimulation is a common cause; for example, rubbing closed eyes or applying pressure to the eyeball can stimulate the retina’s photoreceptor cells. This mechanical pressure causes the cells to fire electrical signals, which the brain interprets as light, leading to the familiar experience of “seeing stars” or patterns. Similarly, a sudden blow to the head can also induce these visual sensations due to the pressure exerted on the eye.
Phosphenes can also occur with rapid eye movements, especially in a dark environment, as the eye adapts to changing light levels. Other everyday actions that can cause phosphenes include sneezing, coughing, or straining, which temporarily increase pressure within the eye.
When Phosphenes Signal a Problem
While often benign, phosphenes can sometimes signal an underlying medical condition. If phosphenes are persistent, new, or accompanied by other symptoms, medical evaluation is advisable. A significant concern is retinal detachment or tears, where the vitreous gel pulls away from the retina, causing flashes of light, sometimes with new floaters or a “curtain” over vision. This requires prompt medical attention to prevent permanent vision loss.
Optic neuritis, an inflammation of the optic nerve, can also cause phosphenes. These phosphenes might be related to eye movements and can be a symptom of neurological conditions like multiple sclerosis. Additionally, visual symptoms, including phosphenes, are a common part of a migraine aura, appearing as flashes or zigzag patterns before or during a headache. While migraine auras are usually temporary, persistent or atypical visual disturbances should be evaluated. Conditions like diabetes-related retinopathy, age-related macular degeneration, or low blood pressure can also be associated with phosphenes. Professional assessment is important when these visual phenomena occur frequently or with other concerning symptoms such as dizziness, weakness, or vision loss.