Seeing flashing lights or patterns when your eyes are closed is a common experience. While it can sometimes be startling, this phenomenon has a range of explanations, from harmless physiological responses to indicators of underlying medical conditions. Understanding these various causes can help demystify the experience and guide individuals on when to seek professional advice.
Benign Visual Phenomena
Phosphenes are light sensations that occur without actual light entering the eye. They can be generated by mechanical stimulation, such as rubbing your eyes, which physically stimulates retinal cells. Sudden eye movements, like saccades, can also induce phosphenes due to mechanical forces on the retina. These sensations result from the visual system’s normal activity when stimulated by something other than light.
Dark adaptation, where the eyes and brain adjust to low-light conditions, is another factor. As the visual system becomes more sensitive in darkness, it can amplify neural noise, leading to the perception of visual static, flickering, or graininess. This internal noise, sometimes called “dark light,” originates within the retina.
Retinal afterimages can also contribute to seeing flashes. After exposure to a strong light, photochemical activity in the retina can persist even after the stimulus is removed. These lingering impressions can appear as positive afterimages, retaining the original color, or negative afterimages, showing complementary colors.
Ocular Health Considerations
Flashes of light when eyes are closed can sometimes indicate specific eye conditions. Posterior Vitreous Detachment (PVD) is a common, age-related change where the vitreous gel, which fills the eyeball, separates from the retina. As the vitreous gel liquefies and shrinks, it can tug on the retina, causing mechanical stimulation that the brain interprets as flashes of light, often described as sparkles or lightning bolts, particularly in dim conditions or the peripheral vision. This pulling on the retina can also lead to the sudden appearance of new floaters, which are visible clumps or fibers within the vitreous.
A more serious concern is a retinal tear or detachment. If the vitreous pulls abnormally on the retina during PVD, it can create a tear. This tear allows fluid to pass underneath the retina, lifting it away from the back of the eye, which is a retinal detachment. Retinal tears and detachments can cause sudden, persistent flashes of light, often accompanied by new floaters that might appear as a “shower of pepper” or a dark curtain in the vision. These symptoms require immediate medical attention to prevent permanent vision loss.
Ocular migraines, also known as retinal migraines, are an eye-specific condition that can cause visual disturbances. These involve temporary visual symptoms in only one eye, such as blind spots, zigzagging patterns, shimmering or flickering lights, or floating lines. These visual symptoms last between 5 and 60 minutes and may or may not be accompanied by a headache. Ocular migraines are distinct from general migraine auras because their visual effects are confined to a single eye.
Broader Medical Conditions
Beyond eye-specific issues, flashing lights can sometimes be linked to broader medical or neurological conditions.
Migraine with Aura
Migraine with aura, often called a classic migraine, involves neurological visual disturbances that affect both eyes. These “auras” can manifest as bright flashing lights, zigzag lines, shimmering spots, or temporary blind spots, usually preceding or accompanying a headache. This phenomenon is caused by a wave of electrical or chemical activity spreading across the brain’s visual cortex.
Transient Ischemic Attacks (TIAs)
Transient Ischemic Attacks (TIAs), or “mini-strokes,” are caused by a temporary disruption of blood flow to the brain, which can cause sudden visual disturbances, including flashes. TIA visual symptoms can include sudden vision loss, blurred vision, or double vision in one or both eyes, resolving within a few hours. While temporary, a TIA serves as a warning sign, indicating a higher risk of a future stroke.
Certain Medications
Certain medications can also induce visual disturbances, including flashes, as a side effect. Various prescription and over-the-counter drugs can cause shimmering lights, halos, or a bluish tint to vision.
Seizure Activity
Seizure activity can also cause visual auras, including the perception of flashing lights. These auras are a type of focal seizure, originating in a specific part of the brain. Visual symptoms during a seizure aura can range from simple flashes or colored spots to more complex hallucinations, and they may serve as a warning sign before a more generalized seizure occurs.
When to Consult a Professional
Individuals experiencing new or concerning flashing lights should seek medical attention. Immediate urgent care or emergency evaluation is advisable if flashes are sudden, persistent, or accompanied by other serious symptoms. These include:
New floaters, a dark curtain or shadow obstructing vision, or any loss of peripheral vision.
Flashes occurring after head trauma.
Neurological symptoms like weakness, numbness on one side of the body, or speech difficulties.
For persistent but non-alarming flashes, or any new visual symptom causing concern, a non-urgent consultation with an eye care professional or general practitioner is appropriate. This allows for a thorough evaluation to determine the cause and rule out any serious underlying conditions. During an examination, an eye doctor will perform a dilated eye exam to assess the retina.
While many instances of flashing lights with closed eyes are benign, understanding the potential causes is important. Prompt evaluation by a healthcare professional can ensure that any serious conditions are identified and addressed early, safeguarding vision and overall health.