Seeing flickering lights, streaks, or flashes that are not actually present is a visual phenomenon known medically as photopsia. This symptom indicates that something is stimulating the light-sensing parts of the eye or brain, which the visual system interprets as light. While the experience can be alarming, the underlying causes range from common, harmless events to serious conditions requiring immediate medical attention. Understanding the source of the flashes is the first step toward determining the necessary response.
The Physical Explanation of Seeing Light Flashes
The mechanism behind seeing light flashes often involves the eye’s internal structure, specifically the retina and the vitreous humor. The retina is the light-sensitive tissue at the back of the eye that converts light into electrical signals sent to the brain. The vitreous humor is the clear, gel-like substance that fills the center of the eyeball, maintaining its shape and supporting the retina.
As a person ages, the vitreous humor naturally begins to shrink and liquefy, causing it to pull away from the retina. The retina responds to any stimulation, whether actual light or mechanical tugging, by firing electrical impulses. When the shrinking vitreous gel pulls or creates tension on the retina, the retinal cells send these signals.
The brain interprets these impulses as light, even though no outside light source is involved. This mechanical stimulation creates the perception of flashes, often described as quick sparks, lightning streaks, or a camera flash in the periphery of vision. This process explains many common, age-related causes of flickering lights.
Causes Related to Headaches and Temporary Stress
Flickering lights are frequently a sign of a neurological event rather than a structural problem within the eye. A common cause is the visual aura associated with a migraine, sometimes called an ocular migraine or a migraine without headache. These visual disturbances, known as scintillating scotomas, manifest as shimmering lights, jagged lines, or geometric patterns.
The pattern usually starts small near the center of vision, then expands across the visual field over 20 to 30 minutes before fading completely. These visual events can occur without subsequent headache pain, which is termed an acephalgic migraine. This photopsia is caused by a temporary wave of altered electrical activity spreading across the visual cortex in the brain, not by a physical pull on the retina.
Other transient triggers can cause temporary light sensations, sometimes called phosphenes. A sudden drop in blood pressure, such as from standing up too quickly (orthostatic hypotension), can momentarily reduce blood flow to the visual system, leading to brief flashes. Similarly, a sudden jolt to the head can cause mechanical stimulation of the retina, which is the origin of the expression “seeing stars.” These occurrences are isolated, resolve quickly, and are distinct from persistent flashes associated with retinal issues.
Urgent Conditions Involving the Retina and Vitreous
The most frequent cause of flashes, particularly in individuals over 50, is Posterior Vitreous Detachment (PVD), an age-related separation of the vitreous gel from the retina. PVD often causes new, sudden flashes and floaters. In most cases, this separation occurs cleanly and is a benign part of the aging process. The flashes caused by PVD are typically quick, like a lightning streak or camera flash in the side vision, and may decrease in frequency over a few weeks or months.
The danger arises when the vitreous gel is abnormally sticky or attached to the retina, pulling hard enough to tear the delicate tissue. A Retinal Tear or Retinal Detachment is a medical emergency because the retina must remain attached to the underlying tissue for oxygen and nourishment. If a tear occurs, fluid can pass through the opening and accumulate behind the retina, causing it to peel away.
The flashes signaling a tear or detachment are often described as a sudden, dramatic increase in the number and intensity of the lights, sometimes accompanied by a shower of new floaters. The most severe symptom is the appearance of a dark shadow, curtain, or veil that blocks a portion of the field of vision. This visual obstruction indicates that the retina has detached, and the corresponding area of vision has ceased functioning.
Guidance on Seeking Professional Care
Any new onset of flickering lights or flashes warrants an examination by an eye care professional, such as an optometrist or ophthalmologist, to rule out serious retinal issues. A dilated eye exam is the only way to fully visualize the retina and confirm the source of the photopsia. This examination allows the doctor to differentiate between a harmless PVD and a sight-threatening retinal tear or detachment.
Immediate, emergency care is necessary if the flashes are sudden, numerous, or accompanied by a significant increase in floaters, a shadow, or vision loss. These symptoms suggest an active pull on the retina or a possible detachment, requiring urgent treatment to prevent permanent vision loss. If the flashes are isolated, recurring, and follow the characteristic pattern of a migraine aura, a routine eye check-up is still advisable to confirm the diagnosis and ensure the retina is healthy.