Seeing flashes of light, often described as “seeing stars,” immediately after a sneeze is a common experience. While this sensation can be momentarily startling, it typically represents a harmless physiological response to the rapid changes occurring within the body during a sneeze. This phenomenon, known scientifically as phosphenes, involves the perception of light without actual light entering the eye.
The Body’s Response to a Sneeze
A sneeze is a powerful and rapid involuntary expulsion of air from the lungs through the nose and mouth, designed to clear irritants from the nasal passages. Before the expulsion, a deep breath is taken, followed by the closure of the vocal cords and a sudden increase in pressure within the chest and abdomen.
This buildup of intrathoracic and intra-abdominal pressure is significant, with studies showing that the force exerted during a sneeze can be comparable to that during moderate-intensity exercise. The pressure surge results in a temporary elevation of blood pressure throughout the body, including the head. As the sneeze culminates, the vocal cords open, and air is forcefully expelled, leading to a rapid release of this accumulated pressure.
The sudden fluctuations in pressure and blood flow can momentarily affect the delicate circulatory system supplying the head and eyes. This rapid change can lead to a brief alteration in blood flow to the brain and retina. While usually benign, this pressure change is a key factor in the visual sensations experienced.
Why You See Stars
The visual phenomenon of “seeing stars” after a sneeze is caused by phosphenes. This occurs because the sudden, intense pressure changes during a sneeze can momentarily stimulate the cells of the retina at the back of the eye, or the optic nerve which transmits visual information to the brain. The brain interprets any stimulation from the retina as light, even if no actual light is present.
Specifically, the temporary increase in blood pressure and the mechanical pressure exerted on the eyes during a forceful sneeze can trigger these visual signals. The vitreous gel inside the eyeball can also be momentarily jostled, potentially rubbing against the retina and stimulating it. Additionally, the vagus nerve, which influences heart rate and is involved in the sneeze reflex, may play a role by contributing to the transient changes in blood flow and pressure that affect the visual system. This brief alteration in blood supply or direct neural stimulation leads to the appearance of flashes, sparks, or dots of light.
When to Consult a Doctor
While seeing stars after a sneeze is typically a harmless event, certain accompanying symptoms warrant medical attention. If the visual disturbances are persistent, do not resolve quickly, or become more frequent, consult a healthcare professional.
Other concerning signs include a significant increase in flashes or floaters, new or prolonged visual disturbances, or any form of vision loss. If the “stars” are accompanied by symptoms such as a severe headache, dizziness, loss of consciousness, or if you have recently experienced a head injury, seek immediate medical advice. These symptoms could indicate a more serious underlying issue, such as retinal detachment or other neurological conditions, requiring prompt diagnosis and treatment.