Phosphenes are visual sensations of light that occur without external light entering the eye. They represent an internal phenomenon, where light is perceived due to stimulation of the retina, optic nerve, or parts of the brain involved in vision. This experience can happen even when eyes are closed or in complete darkness.
The Visual Characteristics
Phosphenes present diverse visual appearances, often described as flashes of colorful light. Colors vary widely, including white, black, blue, yellow, and green, sometimes encompassing the full rainbow spectrum. They can appear bright, vibrant, shimmering, or twinkling.
Shapes are equally varied, appearing as sparks, flashes, stars, dots, squiggles, or lines. More complex geometric patterns like swirls, halos, rings, or amorphous blobs, including zigzags or checkerboards, are also possible. These visual phenomena can move, flickering, pulsating, drifting across the visual field, or remaining stationary.
Intensity and brightness differ among individuals and circumstances, ranging from dim perceptions to vivid displays. Duration also varies, often appearing as brief flashes that resolve quickly. Some patterns can be sustained for a short period, such as electrically induced phosphenes fading after 10-15 seconds.
Everyday Causes
Phosphenes commonly arise from various non-alarming stimuli. Mechanical pressure, such as rubbing closed eyelids, is a frequent cause, leading to “pressure phosphenes” or “seeing stars.” This mechanical stimulation directly affects retinal cells, generating the light perception.
Sudden changes in body position or pressure can trigger phosphenes. Standing up too quickly, sneezing, or coughing can lead to “seeing stars” due to temporary low blood pressure. This phenomenon, known as orthostatic hypotension, may involve mechanical and metabolic stimulation of visual system neurons.
Migraine auras frequently include visual disturbances, a type of phosphene. These can appear as shimmering zigzag lines, sparkling lights, or blind spots, often preceding or accompanying a migraine headache. Such symptoms typically last less than an hour, commonly 10 to 30 minutes.
The visual system’s adaptation to light levels can generate phosphenes. Rapid transitions from bright to dark environments, or prolonged darkness, can cause these perceptions as the retina adjusts. Electrical stimulation, while not an everyday occurrence, is a known scientific method to induce phosphenes, producing points, spots, or bars of light.
When to Seek Medical Advice
While most phosphenes are harmless and temporary, certain characteristics or accompanying symptoms warrant immediate medical attention. A sudden onset of new, persistent, or increasing flashes of light, especially with a significant increase in eye floaters, can be a warning sign. These symptoms could indicate a serious condition like a retinal tear or detachment, requiring urgent evaluation to prevent permanent vision loss.
Phosphenes accompanied by vision loss, pain, or neurological symptoms beyond a typical migraine aura warrant attention. Flashes of light combined with a “curtain” or “veil” in the field of vision, or peripheral vision loss, signal a medical emergency. Such changes suggest an issue with the retina or optic nerve requiring prompt diagnosis.
Phosphenes occurring after head trauma or an eye injury also require medical assessment. A blow to the head can sometimes cause “seeing stars” which, if persistent or associated with dizziness or blurred vision, should be evaluated by a healthcare professional. Consult a doctor if phosphenes interfere with daily life or cause significant distress, ensuring any underlying condition is identified and addressed.