Seeing flashes of light when you cough, sometimes called “seeing stars,” is generally harmless. This phenomenon results from specific physiological responses within the eye and brain.
The Science of Cough-Induced Flashes
Coughing increases pressure in the chest and abdomen, temporarily affecting blood flow and pressure in the head and eyes. These visual disturbances are phosphenes, the perception of light without actual light entering the eye.
Mechanical pressure from a cough stimulates photoreceptors in the retina, the eye’s light-sensing tissue. This causes retinal cells to fire electrical signals, which the brain interprets as flashes or streaks of light. This is similar to seeing lights after rubbing your eyes, as both involve mechanical pressure.
Distinguishing Harmless from Concerning Flashes
Most cough-induced flashes are temporary and benign, resulting from brief mechanical stimulation of the retina. They typically last only a few seconds and do not cause lasting vision changes. These flashes are particularly noticeable in darker environments, where the eye is more sensitive to light.
However, flashes of light with other symptoms can indicate a more serious eye condition. Posterior vitreous detachment (PVD) is an age-related condition where the vitreous gel separates from the retina. While PVD is usually harmless and causes flashes or floaters, pulling on the retina can sometimes lead to a retinal tear.
A retinal tear, if untreated, can progress to a retinal detachment, a medical emergency where the retina pulls away from its supporting tissues. Symptoms warranting immediate medical attention include a sudden increase in floaters, persistent flashes, a dark shadow or “curtain” in your vision, or sudden vision loss. Prompt evaluation by an eye care professional is needed to prevent permanent vision loss.
General Advice and Next Steps
If you experience new, frequent, or accompanied flashes of light when coughing, consult a healthcare professional. An eye care specialist can examine your eyes to determine the cause and rule out serious conditions. Early diagnosis and treatment of retinal tears or detachments can help preserve vision.
Addressing the root cause of the cough may also help alleviate the associated visual flashes. For example, treating coughs due to allergies, infections, or acid reflux could reduce the frequency or intensity of coughing fits and, consequently, the eye flashes.