Phosphenes are the perception of light or visual sensations without any actual light entering the eye, occurring even when your eyes are open. The term “phosphene” originates from Greek words: “phos,” meaning light, and “phainein,” meaning to show.
Understanding Phosphenes
Phosphenes can manifest in various forms, appearing as flashes, sparks, geometric patterns, or streaks of light. Some individuals describe them as rapidly moving stars, shimmering, twinkling, or glittering lights, while others might see floating shapes, dots, or even “snow” or “static” in their visual field. These visual phenomena originate from the stimulation of the retina, the light-sensitive tissue at the back of the eye, or from the visual pathways in the brain. The brain interprets these internally generated signals as light.
Common Triggers of Phosphenes
Several common factors can cause phosphenes.
Mechanical pressure on the eye is a frequent cause. Rubbing your eyes, for example, can stimulate retinal photoreceptor cells, leading to transient flashes or patterns. These pressure-induced phosphenes can sometimes persist briefly after the pressure is released.
Sudden changes in blood pressure can also trigger phosphenes. Common examples include “seeing stars” after standing up quickly, sneezing, laughing, or a heavy cough. These instances may involve mechanical and metabolic stimulation of visual cortex neurons, potentially due to temporary low oxygenation or lack of glucose. Such occurrences are usually brief and harmless.
When Phosphenes Signal a Health Concern
While many phosphenes are harmless, their presence can sometimes indicate an underlying medical issue, particularly if they are new, persistent, or accompanied by other symptoms.
Retinal detachment is a serious condition where the retina pulls away from its supporting tissue. This can cause a sudden onset of flashes, often accompanied by a sudden increase in “floaters” (small specks or cobwebs in your vision) or the sensation of a “curtain” coming across your field of vision. Immediate medical attention is necessary if these symptoms appear.
Ocular migraines, also known as retinal migraines, can also cause visual disturbances resembling phosphenes, often affecting only one eye. These visual auras may involve flickering lights, zigzag patterns, or temporary loss of vision in one eye, and may or may not be followed by a headache.
Optic neuritis, inflammation of the optic nerve, can lead to phosphenes, sometimes associated with eye movement. Other symptoms may include blurred vision, pain when moving the eyes, or loss of color perception.
Brain lesions or ischemia can also produce phosphenes, sometimes affecting both eyes. Seek prompt medical evaluation if phosphenes are new, increase in frequency or intensity, or occur alongside vision loss, eye pain, or other neurological symptoms.