Photopsia, or seeing stars in your vision, describes the perception of flashes of light, sparks, or streaks without an external source. While often temporary and harmless, this common experience, which can appear as brief bursts or zigzag lines, sometimes signals underlying health issues.
How the Eye Interprets Light
Vision begins when light enters the eye and is focused by the cornea and lens onto the retina, a light-sensitive tissue. The retina contains photoreceptors (rods and cones) that convert light into electrical signals. Rods handle low-light vision, while cones are responsible for color and fine detail.
These signals travel along the optic nerve to the brain’s visual cortex, where they are interpreted as images. When the retina or visual pathways receive physical or electrical stimulation without actual light, the brain can interpret these signals as “light” or “stars,” causing photopsia.
Everyday Reasons for Seeing Stars
Some instances of seeing stars are common and not a cause for concern. Mechanical stimulation, such as rubbing your eyes vigorously, can trigger these light perceptions by momentarily activating photoreceptors, causing a brief flash.
Similarly, sudden actions like sneezing or coughing forcefully can induce temporary photopsia due to increased pressure within the head and eyes. Another harmless cause is orthostatic hypotension, a temporary drop in blood pressure when standing up too quickly. This reduces blood flow and oxygen to the brain and eyes, resulting in momentary dimming of vision or flashes.
Medical Conditions That Cause Flashes
Persistent or new flashes can signal medical conditions requiring prompt evaluation. Migraines with aura often involve visual disturbances like flashing lights, shimmering zigzag lines, or blind spots that precede the headache. These visual changes typically last between 10 to 60 minutes and are thought to be caused by abnormal electrical activity in the brain.
Posterior vitreous detachment (PVD) is a common age-related condition where the vitreous humor, the gel-like substance filling the eye, liquefies and shrinks. As the vitreous pulls away from the retina, it can tug on the tissue, causing flashes, often described as lightning streaks, and new floaters. While PVD itself is usually harmless, the pulling can sometimes lead to a retinal tear.
A retinal tear or detachment is a more serious condition where the retina pulls away from its supporting tissues, potentially leading to permanent vision loss if untreated. Symptoms include a sudden increase in flashes, new floaters that might resemble a “shower” of specks or a large “cobweb,” or a shadow or “curtain” obscuring part of the vision. These symptoms indicate an urgent need for medical attention.
Head trauma, like a concussion, can also cause photopsia by disrupting the brain’s visual processing. A blow to the head can scatter nerve signals, leading to temporary visual disturbances like flashes or bright spots.
When to Seek Medical Attention
While occasional flashes are often benign, certain symptoms warrant immediate medical evaluation to rule out serious conditions. Seek prompt attention if you experience a sudden onset of new flashes, especially if their number or intensity significantly increases. This is particularly true if flashes are accompanied by new floaters, such as many small specks or a large, cobweb-like shape.
The appearance of a “curtain” or “shadow” obscuring any part of your vision, or flashes after head trauma, also signals a need for urgent care. Any persistent flashes, or visual changes that cause concern, should prompt a consultation with an eye care professional. These symptoms could indicate a retinal tear or detachment, conditions that require timely treatment to preserve vision.